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(C4) OCR 21st Century GCSE: Chemical Patterns

The Elements - The Periodic Table & Atomic Structure - Flame Colours & Spectra - Alkali Metals - Halogens - Displacement Reactions - Properties of Salts - Ionic Theory - Atoms Into Ions - Chemical Equations
by

J Amuah-Fuster

on 18 October 2016

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Transcript of (C4) OCR 21st Century GCSE: Chemical Patterns

Atomic Structure
Reactions of Alkali Metals
Group 1:
The Alkali Metals

C4: CHEMICAL PATTERNS
Sodium oxide
Magnesium chloride
Lithium oxide
Calcium fluoride
Potassium chloride
Iron(III) oxide (HINT: Iron ion has a +3 charge)
A lithium atom has a diameter of just 0.33 nm.
1 nm is
one billionth
of a metre or 1 x 10 m.
Atoms are so small that even with a powerful microscope we cannot see what they are made up of.
-9
The Periodic Table
Electronic Structure
& the Periodic Table

Flame colours & Spectra
Atoms into Ions
Periodic table
On the periodic table use different colours to shade in the elements which, at room temperature, are;
solids
liquids
gases
Add a title and key

On the periodic table:
draw the 'stair case' in and label metals on one side and the non-metals on the other side.
Label the groups (the alkali metals (Group 1), the alkaline earth metals (Group 2), the transition metals (between Groups 2 and 3), the halogens (Group 7), the noble gases (Group 0))
Starter
Define the term element

Where can we find a list of all the discovered elements?

Name an element that is:
a liquid,
a solid,
a gas

Suggest two elements that have similar properties. Why have you suggested this?
C4 L1: Elements in Order
To recall how the elements are ordered in the modern periodic table

Explain how Dobereiner, Newlands & Mendeleev developed the modern periodic table

Use key terms; atom, group, period, atomic mass, atomic number [proton number])
Bingo!
Write down the symbols for any 9 of the first 20 elements in a 9 x 9 grid
He lined up all the known elements
in order of their relative atomic mass
.

He spotted that
at intervals
along the line there were
elements with similar properties
(
periodicity
)

and put them in the
same group
.

He realised
not all elements had been discovered
and
left gaps
.

He could
predict the properties
of the missing elements.
Homework
Task: Make a note of three interesting findings about the Periodic table. Prepare to report on them.

You should:
Explore two or three of the websites. This will show the range of information available on the Internet.
Look out for anything that you find particularly interesting. This might be an interesting fact, idea, or story about:
an element you already know something about
an element that you knew nothing about before you started
the discovery and naming of elements
the discovery and development of the periodic table
something that you come across by chance
Try these websites:

Webelements

Royal Society of Chemistry

University of Nottingham
Write a brief account of your findings to show which of the arrangements brings the chemical families together most clearly.
Chemical family cards
Repeat step 2, keeping the cards in increasing order of density until you have placed all 20 cards in as many family groupings underneath each other as possible.
Make a note of your arrangement using the chemical and family symbols only.
Evaluating scientific ideas - 6 mark question
Reactions of the Halogens
Properties of Salt
The
positive
and
negative
ions are
attracted
to each other due to
electostatic force
.
Each ion attracts oppositely charged ions from all directions.
Each of these, in turn, attracts more ions, arranging them in a
regular pattern
.
Millions of ions come together to form a giant ionic structure (
giant lattice
) to form solid
crystals
as a result.
Ionic Theory
Group 7:
The Halogens

Look at the figures for density on the cards
Arrange the cards in order of increasing density, with the lowest (hydrogen) first.
Look along the cards in order.
When you come to an element that has the same family symbol as one that has gone before it, take that card and place it in a column directly below the first one.
Now take the rest of the row and bring all the cards down to the new level.
Repeat this process for each set of data: melting point, and relative atomic mass. Make a record of each arrangement.
Ca
K
Br
Assuming room temperature is 25 degrees celsius
What is your favourite element and why?
Standardised assessment Qn4
Plot the
melting point
(y axis) of the alkali metals (lithium, sodium, potassium, and caesium
)

against

proton number
(x-axis).
Use your chart to
predict the melting point of rubidium
.
Describe the
trend in melting point down group 1
from lithium to francium.
Plot
bar chart
of
melting points (
y axis
) against proton number (
x axis
)
of elements (from
lithium to argon
) show a repeating (periodic) pattern when plotted against proton number.

Draw a vertical line to
split the chart into periods
(after, Ne, Ar).
Label these periods 2 and 3
.

Now write a paragraph to
describe the trend in each period
.
Explain
how this shows a
Periodic pattern
.
To interpret patterns in chemical data

To explain what is meant by a periodic pattern
Which of these substances are
solid
at 130 degrees celsius?

Which of these substances are
liquid
at 105 C?
A similar pattern is observed in period 3, with exceptions; at proton number 13, the melting point is not as high as expected, while the melting point is too high at 16.
Period 3
Period 2
Alkali metals
Halogens
Answer
The melting point of metals does increase, but not proportionally (Mg and Al are very similar)
[1]
The melting point of non-metals decreases, with the exception of Sulfur, which is greater than Phosphorus
[1]
Further data required would include trends in melting points across other periods in the periodic table to observe if a similar trend is seen
[1]
Lesson Objectives
The
protons
and
neutrons
are
in the centre
of the atom.
This is the
nucleus
.
neutrons
(no charge), mass = 1
protons
(positively charged), mass = 1
Almost
all the mass
of the atom is
in the nucleus
.
In this model
atoms are not solid spheres
. They are made up of
other smaller particles
.
Scientists use a
model
of atomic structure to help to explain the
patterns
in physical and chemical properties.
Questions
With the help of a periodic table, work out:

the element with
one more

proton
in its nucleus
than a chlorine atom

the element with
one proton fewe
r in its nucleus
than a neon atom

the number of
protons
in a
sodium
atom

the number of
electrons
in a
bromine
atom

the number of
neutrons
in a
tellurium
atom

the size of the
positive charge
on the nucleus of a
fluorine atom
Calculating protons, electrons, neutrons
Copy and complete:
Use the periodic table
…so the model we use is not to scale.
The nucleus is actually like a 5p piece in the middle of a football pitch.
C4 L3 Atomic structure
describe the structure of an atom

give the relative masses and charges of protons, neutrons, and electrons

use information from the periodic table to work out the number of protons, electrons, and neutrons in an atom
Protons, electrons, neutrons
Neutrons
charge =
0
mass =
1
Protons
charge =
+1
mass =
1
An atom is made up of:
 

 

 

1
 

 

 

Nucleus

protons and neutrons
.
Has the mass
Particle
Mass
proton
negative
Charge
Copy & complete the table.
Sub-atomic particles
Use the table to answer the following questions using letters A-D:
What is the value of x? ………
Which element is from group 7? ………
Which elements are in the same group? ……… & ………
Exam question
In pairs, complete the sheet
First 20 elements sheet
What do you notice about the electronic configuration of all the elements in group 1?


What about group 7?


What do you notice about the electronic configuration of all the elements in period 2?


What about period 3?
Starter
Electronic configuration
Magnesium has
12 protons
, meaning it's
atom
has
12 electrons
as well.
Writing the electronic configuration
Why was it important that Bunsen invented this new burner?

What is the importance of the spectroscope?
Discovery of new elements- 6 marks
In 1868 there was a total eclipse of the Sun. During the eclipse, then Moon hides the whole bright disc of the Sun but not the much fainter light from the hot gases around the edges. This makes it possible to study the light from these gases and so Helium was discovered.

Explain how the discovery of new elements (for example Helium) depended on the development of new practical techniques. In your answer you should refer to:
Bunsen Burner
Spectroscope

and explain what evidence these practical techniques provided.

The quality of written communication will be assessed.
A solar eclipse in 1868 helped scientists to discover
helium
.
During an eclipse it is possible to study the spectra of the light from the hot gases around the edges of the Sun
Spectra – series of lines (
fi
ng
er

pr
int
of an element)
Sp
e
c
t
r
o
s
c
o
p
e

splits
the
coloured light
into component parts
When elements are subject to ________, their electrons absorb the energy.

They then give this energy out as ________ at specific frequencies.

The frequency of light corresponds to a specific ________.
Lots of elements show similar colours though…
When heating, use the
blue flame

why
?
Lesson Objectives
Recall the flame colours of the elements and the key turn ‘line spectrum’.

Explain ho that the discovery of some elements depended on the development of new practical techniques.
Set up a Bunsen burner on the
safety flame
What are the trends down the group?
In terms of melting and boiling point?

In terms of reactivity

What would you predict about the physical and chemical properties of Francium (Fr)?



What are the
differences
in the group 1 alkali metals?
What are the
similarities
in the group 1 alkali metals
Think about:
Appearance

Reaction with
oxygen
Softer (easier to cut)
Decreasing melting and boiling points
Trends down the group
Physical
properties

Lesson Objectives
To recall the physical properties of group 1 (alkali metals)

To recall the similarities and differences in the way they react (observations and equations)
Draw the electronic configuration for Li, Na and K
To do:
K
Na
Li
...and electrons
(negatively charged),
mass = 1/1860

OCR 21st Century GCSE
1. Cut out the hazard names, descriptions, and chemicals.
2. Stick the name, description and TWO chemicals in the relevant place on each hazard symbol
3 Under each hazard box, write down a suggested safety precaution when using a chemical labelled with the hazard symbol.
Hazard Symbols & Safety
Look at the trend in the boiling points of the halogens.
What is your prediction for the boiling point of fluorine?
Predictions
Recall and recognise the
chemical symbols
for the
halogens
and their
states
of matter. Recall the colours of the Group 7 elements at room temperature and pressure

Recall that the halogens consist of
diatomic
molecules

Recall the
main hazard symbols
and be able to give the
safety precautions
for handling hazardous chemicals (limited to
explosive, toxic, corrosive, oxidizing,
and
highly flammable
)
Learning Objectives
How would you handle the Halogens?
The halogens are
diatomic
.
Meaning each
molecule
is made up of
two atoms
.
The Halogens
Symbols
Metals / non-metals?
States of matter
Appearance
Uses
Electronic Configuration
Draw a spider diagram in your book of as many facts about the halogens as you can think of (make use of your Periodic Table)
Starter
The Halogens
Chlorine + Potassium bromide

Bromine + Potassium chloride
To finish: Answer questions 1 and 2 on page 113 of textbook

What did you find out?

Complete the practical and answer the questions: You have 20 mins

Safety precautions

- Wear eye protection

- Use chlorine and bromine in a fume cupboard (toxic gases)

- Wear gloves when handling bromine (corrosive)



What safety precautions should we take when working with the halogens?

Group 7 elements are also known as the _________. As you go ______ this group the elements become ______ reactive. This trend can be shown by their reactions with the ________ metals and iron.

For example, chlorine reacts violently with _______, burning with a bright orange flame. In contrast the reaction between _______ and sodium is much less violent.
Try the exam question:
General halogens questions
What kind of
compound
is
formed
when a
metal reacts
with a
halogen
?
Displacement reactions -
word and symbol equations
Potassium + chlorine bromine + potassium
bromide chloride


Potassium + chlorine
iodide


Potassium + bromine
iodide
Practical Ac4.6.1 - Hazards
For each chemical you are going to use

-note down the hazard symbol

-note down the precaution you will take
Conclusion...
Which is most reactive chlorine, bromine, or iodine?

Which of the salt solutions did bromine react with?

Write an equation for this reaction.

Explain the results you observed for the reactions involving iod
ine
?

Do you think fluorine would react with a solution of potassium chloride? Explain your answer

Learning Objectives
Identify patterns in data and use this to make predictions (today data from the practical)

Explain what this trend shows

Recall and explain the safety precautions necessary when working with the halogens
Draw the following results table
Record the colours
Put the halogens in
order of reactivity
(least to most)
Write down the colour of the vapour for
four
of the halogens
Cl
F
I
At
Br
Starter
The formula of a water molecule is H O.
The formulae of hydrogen and oxygen are diatomic, meaning the atoms travel in pairs, H and O .
Chemical Equations
The Elements in Order
Compare the
properties
and
appearance
of sodium and chlorine with sodium chloride. (6 marks)
Metals
react with
non-metals
to form
salts
.
When
sodium
reacts with
chlorine
, it makes
sodium

chlor
ide
.
Which is the metal and which is the non metal?
Salts
Ionic salts are compounds of _____ with ___-______.
Salts produced from the reaction between a metal and non-metal have very ____ melting/boiling points.
Salts produced from alkali metals and halogens are often __________ in appearance.
These salts can be _________ in water to form a salt solution.
The salt solution can _______ electricity because the elements making up the salt can be split into ____ that are free to ____. As a result, these ions allow electricity to pass through the solution.
Copy & Complete
Instructions Team 2
The structure of salts
Ions
= positive and negative atoms

Ionic structure
= structure made of ions bonded together


Crystals
Lattice structure
The shape of salt
Crystals of sodium chloride
A sodium chloride crystal is made up of
millions

of

Na+ and Cl− ions
arranged in a
regular pattern
.
The regular pattern is responsible for the cubic shape of all sodium chloride crystals.
Produces hydrochloric acid and bleach
Produces sodium hydroxide and hydrogen
Solid
Conducts when molten
Insulator
Metal
Salt
Dissolves to form a solution
Conductor
Hard
N/A
Soft
Silvery
White
Pale green/yellow
Gas
Non-Metal
All of the answers are scattered on the slide – check your answers
Back to the table from the start
Chemical properties
Solid – can’t conduct because ...
the ions in solid potassium iodide can not move
solid potassium iodide has a regular/fixed lattice arrangement of the ions
Dissolves – can conduct because ...
If the ionic compound dissolves it can conduct electricity because the charged ions can move
(independently) among the water molecules
Molten – can conduct because ...
When the ionic compound is heated, the ions move so much that they can not stay in the regular arrangement/ lattice destroyed on melting
Because the charged ions can now move (independently) the compound can conduct electricity
Stack up your books in the middle of the row
Pens down!
Four minutes of time to read through the information sheet
You will need to understand and be able to recall this information
Why do ionic salts conduct electricity when molten/dissolved?
Can you draw the electron configuration of the ions in sodium chloride (Na+ and Cl-).
RULE: Electrons are lost/gained on the
outer shell first
Task
Work in pairs with the person next to you
Assign one person to be the describer and one person to be the guesser
The describer must describe the chemistry word in bold without using the other keywords displayed (do not let the guesser see the card).
Record how many words are correctly guessed in your pair – prize for the winner
If finished make your own set of cards for another group to use **(1xmerit)**

C4 Chemistry Taboo

Complete the exam question under controlled conditions
3 minutes reading time + 5 minutes to answer
6 Mark Exam Question
Can you draw the electron configuration of sodium and chlorine?
Electron Configuration Recap
Using the purple pens
Starter
Lattice Structure
Explain that salts consist of ions

Use ionic theory to explain the conductivity of salts when molten or in solution
Lesson Objectives
Cl
Na
An
ion
is an _____ that has _______ or _______ electrons so it has an overall ________ .

Positive
ions have _______ an electron
Negative
ions have _______ an electron

Salts are made of positive ions and a negative ions, e.g. sodium chloride, __________ to each other due to __________ charges
Ions
Draw the structure of sodium chloride
Can you use the words
electrostatics
,
lattice
and
crystal
to describe the structure of the salt sodium chloride?
Which element does the Na+ ion now have the same electronic configuration as?


Which element does the Cl- now have the same electronic configuration as?


Can you see a pattern?
Explain, using diagrams and keywords, why ionic salts only conduct electricity when molten/dissolved?
Can you
design an exam question
that can be used as a starter for a student in the next lesson?
Four mark question
so
4 points or calculations needed
as a rough guide.
Be as creative as you like – fill in the gaps, drawing examples, etc.

Success Criteria
– does one of:-
Takes students through the formation of ions in terms of electron configuration
Gets students to calculate the charge of an ion
Gives students practice at working out the formula of compounds
Make your own Exam questions
Exam question
Work out the electronic structure of each ion.
What is the
charge
on each ion.
How many of each ion do we need to make a
neutral
compound
What is the formula for…
Complete as much of the table as you can
Draw a diagram to show the arrangement of electrons in a lithium ion (same group as sodium)

Draw a diagram to show the arrangement of electrons in a fluorine atom (same group as chlorine)

For each on, state how many protons and electrons it has
Starter
Learning Objectives
To distinguish between
atoms
and
ions

To work about the
formulae
of a compounds using the
charges
on the ion
To get an overall charge = 0, we need;
2+
Making formulae
The
charges of the ions must balance
to make
neutral
compounds
You need to work out the
ratio

of each element
to make this true.
E.g.
Making formulae
Ions have a
stable

outer shell
of electrons. They have the
same electron configuration
as
noble gases
(group 0 or8).
Protons: 17, electrons:
18
Protons: 11, electrons:
10
Ion

Protons: 17, electrons: 17
Protons: 11, electrons: 11
Atom

What happens when an atom forms an ion?
+8p – 10e =
-2
+12p – 10e =
+2
Lost 2
electron so
2+
Ion
Protons: +8, electrons: -8
Protons: +12, electrons: -12
Atom
What about the charge?
HMK – writing equations sheet
Write a
word
equation
Write the
correct formula
for each reactant and product underneath (check charges on ions)
Calculate how many atoms
of each element you have on the left hand side and right hand side of the equation.
If necessary,
balance the equation
by putting
big numbers in front
of the formulae
NEVER- Change the formulae
of a compound or element to balance.
Add
state symbols
(s, l, g or aq)
Rules for balancing equations
Salts are solids

unless water is present
(then they are
aqueous

solutions
)
Not sure about symbols
Complete ‘preparing for balancing equations’
Starter

Lithium + oxygen

Sodium + chorine

Potassium + water

Sodium + water sodium hydroxide + water
Examples
Balancing equations mat
Balancing equations: example
Balancing equations: example
In
1800
only about
thirty
elements were known

By
1900
most of the stable elements had been discovered
The Periodic Table
Döbereiner
Law of triads
1817
The History of the Periodic Table
Döbereiner
 arranged
groups
of three elements with
similar chemical properties
, he called these '
triads
'
Relative atomic mass
Different atoms have different masses
.
Atoms have such a
small mass
that it is too
difficult to measure
. So, it is
more

convenient
to know their masses
compared
(
relative
)
to each other
.
Using the information sheet, fill in the table for how Newland and Mendeleev arranged the periodic table
History of the Periodic Table
Newlands arranged the elements in order of:

a) atomic number
b) relative atomic mass
c) their first letter
Quick Quiz
Moseley arranged the elements in order of:

a) atomic number
b) relative atomic mass
c) their first letter
Quick Quiz
Who predicted the properties of undiscovered elements using their table?

a) Dobereiner
b) Newlands
c) Mendeleev
Quick Quiz
1864
1869
1913
1860
1829
Moseley (
modern periodic table
) 1913
KEY IDEA
atomic number
Newlands
octaves
1864
KEY IDEA
relative atomic mass
Newlands arranged them
in order of relative atomic mass
He noticed
every 8th element
had
similar physical properties
.
He called this the '
Law of Octaves
'
Found a way to measure the
number of protons
in an atom (
atomic number / proton number
).
Able to rearrange elements
in order of atomic number
instead of atomic mass
All atoms of the
same element
contain the
same number of protons
.
Arranged in order of
atomic number
(
proton number
)
Mendeleev's
Periodicity
1869
Te and I are not in order in terms of their atomic mass

How are the elements ordered in the periodic table we use today?
In the
modern
Periodic Table, which two elements are not arranged in order of increasing relative atomic mass?
Periodicity is a
repeating

pattern
in
chemical properties
that repeats from period to period (row to row)

Period
= row of the periodic table
Group
= column in the periodic table

The periodic table is now
ordered by atomic number
.
Groups
of elements have
similar properties
.
Periodicity
Johann Döbereiner also showed that the properties of the middle element could be
predicted
from the properties of the other two.
http://www.periodicvideos.com
Rb
o
None of them
What is the state at room temperature?
solid (s)
solid (s)
liquid (l)
gas (g)
Summary
6
19
9
7
4
1
8
6
19
9
7
4
1
8
12
39
19
14
9
1
16
6
19
9
7
4
1
8
6
20
10
7
5
0
8
Argon
Fluorine
11 protons
35 electrons
76 neutrons
+9 charge
Answers
Write these formulae down
Electrons
charge =
-1
mass =
almost
zero
The nucleus of an atom is made up of protons and electrons. All of the mass of an atom is found in the nucleus because protons have a mass of +1 and neutrons have a mass of -1.

The atomic (proton) number of carbon is 12, whereas the atomic (proton) number of scandium is 21.

The number of electrons is always equal to the number of neutrons. As you go down the group 1 metals, the boiling point increases.
List the five deliberate mistakes in the text. Can you correct them?
Use simple conventions, such as 2.8.1 and dots in circles, to represent the electron arrangements in the atoms of the first 20 elements in the Periodic Table

Understand that a shell (or energy level) fills with electrons across a period

Understand that elements in the same group have the same number of electrons in their outer shell and how this relates to group number
Learning Objectives
Our model so far...
Name the element…
Elements in the same group have…


Elements in the same period have…

Complete the sentences…
How many electrons are in magnesium?
Electron Configuration
Draw and write the electron configuration of the following elements:
Calcium
Silicon
Phosphorus
Carbon
Beryllium
Hydrogen

Extension
: read pages 120-121 and answer all three questions
Electron Configuration
On the scrap paper draw the electron configuration of your element nice and big.
Then stick it on the right spot on the board.
Making up the periodic table
The
arrangement of electrons
in these shells is called the
ELECTRONIC CONFIGURATION
Electron Configuration...
explained
Protons
are
positively
charged and
electrons
are
negatively
charged.
Opposite
charges
attract
.
Electrons
will be
attracted

to the nucleus
, they fill the shells nearest because these
require least energy
. If these
shells are full
, the electron must move to the
next closest shell
.
Rules
First shell, 2 electrons max
Second shell, 8 electrons max
Third shell 8 electrons max
Mg
Extension
: write the electronic configurations beneath each diagram
4
B
A
D
Electrons occupy
shells
(
orbitals
)
1st shell? -
Mg has
12
electrons
2nd shell? -
3rd shell? -
2
2
8
Can you help him?
"Why do electrons fill up the first shell first, then the second shell, then the third shell?

Why can’t they just go into any
shell?"
Jimi wonders ...
Where are electrons found in the atom?

What charge do they have?

What mass do they have?
Outside
the nucleus

Negative
(-1)

Negligible (
almost
zero)
Questions
The
same number of electrons
in the outer shell


The
same number of shells
(energy levels)
The nucleus of an atom is made up of protons and
neutrons
. All of the mass of an atom is found in the nucleus because protons have a mass of +1 and neutrons have a mass of
+1
.

The atomic (proton) number of carbon is
6
, whereas the atomic (proton) number of scandium is 21.

The number of electrons is always equal to the number of
protons
. As you go down the group 1 metals, the boiling point
decreases
.
They all have 1 electron in their outer shell.


They all have 7 electrons in their outer shell.



They all have 2 energy levels (shells).


They all have 3 energy levels (shells).
Quick Quiz
Dobereiner grouped the elements based on:

a) similar chemical properties
b) similar relative atomic mass
c) similar first letters
Copy and complete
Keywords
colour heat light
light
colour
heat
HEAT
LIGHT
Electron
jumps
to a
higher

energy

level
Electron
drops
to a
lower energy level
When

heated
,
electrons
in the metal ion
gain energy
and can
jump
into
higher energy levels
. Because this is energetically
unstable
, the
electrons
tend to
fall back down
to where they were before,
releasing energy
as they do so. This energy is released at various frequencies, often
as colours of light
. The
colour
(frequency)
varies between different metal ions
, leading to the characteristic colours of each metal
What do you think his contribution was?
Previously, heating was carried out using spirit burners.
These were glass and often burned alcohol, which could spill and cause
hazardous
fires.
Robert Bunsen designed a gas burner that had an adjustable air hole that could create a safer yellow flame or a much hotter blue flame for heating
In addition, the amount of heat was
difficult to control
.
Answers - mark scheme
What have we learned?
This data shows periodicity because there is a pattern/trend in properties that is repeated across other periods.
The trends seen in period 2 show that melting point increases steeply as proton number increases from 3 to 6. After this, the melting point decreases dramatically and continues to decrease more slowly to proton number 10.
Written Answers
Exceptions
As we go down group 1, the melting point decreases from lithium to francium.
As we go down group 7, the boiling point increases from fluorine to iodine.
Plot the
boiling points
(y axis) of the halogens (fluorine, chlorine, bromine, and iodine)
against

proton number
(x-axis).
Describe the
trends in boiling points down group 7
from fluorine to iodine.
...it helps to be able to
see all the particles
-
protons and neutrons (in the nucleus) and the electrons

at the same time
.
However...
A
cloud

of

electrons
surround the nucleus.
Sodium
Potassium
Fluorine
Phosphorus
Hint
:
the
number of
shells

is

equal
to the
period
in which the element is found
How many protons does lithium (Li) have?
Quick Quiz
All alkali metals react
vigorously
with chlorine to form a
colourless
, crystalline
salt
with the formula
MCl
Reactions with chlorine
Can you complete the general equation for the reaction of all alkali metals with water?


Predict the reaction of Rubidium and Caesium with water.

What is the pattern in reactivity of group 1 metals?

Questions
All the alkali metals react
vigorously
with
cold water
.
Reactions of the alkali metals
Alkali metals have similar reactions
because…?
Increased reactivity with water
Increased reactivity with halogens (group 7)
Chemical
Physical
Metal

+

water

Extension
– have a think about
why
reactivity changes down the group?
General equation for the reaction of all alkali metals with water is:


The reaction of
Rubidium
and
Caesium
with
water
will be
extremely

vigorous
(
Caesium

more

so
).
Rubidium
will form
rubidium

hydroxide
, while
caesium
produces
caesium

hydroxide
. Both will also produce
hydrogen

gas.

As we go
down group 1
the alkali metals become
more reactive
, as
more energy is released
during the reaction.
Answers
metal
+
water

metal

hydroxide
+
hydrogen
Use this information
760
1342
883
2
M
+
Cl
2
M
Cl
(s)
2
(s)
(g)
What alkali metal burst into flames when dropped into water?
How many electrons does sodium have in its outer shells?
What is the group number of the alkali metals?
Which is the most reactive alkali metal?
What is the flame colour of lithium?
Quick Quiz
Quick Quiz
Quick Quiz
Quick Quiz
Quick Quiz
Extension
Reactivity increases down the group because
electrons are further away from the positive nucleus
and so
not attracted so strongly
. They are
more easily removed
for reactions to occur.
Melting and boiling points
decrease
down the group

Reactivity
increases
down the group


Francium's physical properties would show a
lower

melting point
and
boiling point
than K, Rb and Cs. While it's chemical properties would be
similar
to those of Li, Na, K, Rb and Cs -
but much more vigorous / explosive
Lithium has
3 protons
Potassium
burst into flames when dropped in water
Sodium has
1 electron
in its outer shell
Group
number
1
Francium
is the most reactive alkali metal
Lithium (think
li
pstick) is
red
Lithium
Chlorine
Lithium Chloride
x
x
x
x
x
x
x
x
x
purple
green
lithium hydroxide
Na
Rubidium
K
Reaction with
water
Reaction with
chlorine

All alkali metals
have a
dull grey

outside
appearance with a
shiny lustre when freshly cut
.
react readily with oxygen to form their
metal oxide
(dull grey exterior).
react vigorously with water to form their
metal hydroxide
and
hydrogen gas
.
react vigorously with chlorine to produce their
metal salt
.
All the alkali metals react
vigorously
with
chlorine gas
.
F
Cl
Br
I
At
Fluorine -
yellow
Chlorine -
yellow/pale green
Bromine -
red/brown
Iodine -
purple
2KBr + Cl Br + 2KCl
2KI + Cl I + 2KCl
2KI + Br I + 2KBr
Chlorine is most reactive
Yes, fluorine is more reactive than chlorine, so it will displace the chloride, forming potassium fluoride and chlorine
Bromine reacted with potassium iodide
only
2KI + Br I + 2KBr
Iodine is
least

reactive
, it
couldn't displace other halides
from their salts
"The halogens are similar because... "
Discuss in groups
Because they exist as
molecules
with a
pair
of
atoms
, Fluorine molecules have the formula F , chlorine Cl , bromine Br and iodine I .
What might this mean, in terms of their chemical formula?
Exam Practice Qs
All alkali metals react
vigorously
with water to form the
alkaline
,
metal hydroxide
(with the formula
MOH
), and
hydrogen gas
Reactions with water
2
M
+ 2
H O
2
M
OH

+

H
(aq)
2
(s)
(l)
(g)
2
Sodium street lights
Alkali batteries
Floats
on water surface,
fizzes
and
dissolves
Floats
on water,
fizzing
and
sparks
.
Dissolves with popping!
Floats
,
fizzes
and ignites with
lilac flame
-
explodes!!
Needs

lots of heat
to start. Displays
light
, produces
colourless
(not white)
crystalline solid
Needs

little

heat
to start. Produces
very bright light
,
colourless

crystalline solid
made
Needs

moderate

heat
to start.
Lots of light
seen,
colourless crystalline solid
produced
Lithium hydroxide + Hydrogen gas
Potassium hydroxide + Hydrogen gas
Sodiumhydroxide + Hydrogen gas
Lithium chloride
Sodium chloride
Potassium chloride
Write the formula for all five halogens
Keywords:
alkali
down
halogens
iodine
less
sodium
Reactions of the halogens
Fill in the gaps
halogens
sodium
iodine
alkali
down
less
New uses of the halogens
Uses of halogens
Physical properties of halogens
These are also the
colours
of the halogens
2
2
2
2
2
2
iodine + potassium
chloride


iodine + potassium
bromide
Write word and symbol equations for all of the reactions where there was a change.
Equations
E.g.
Molecules of the halogens have two atoms; (F–F, Cl–Cl, Br–Br, I–I). The
bonds between the atoms
in the molecules are
strong
.
How
can you account for the fact that all
halogens easily become gases
?
What
test
could you do on an iodine crystal to confirm that iodine is a
non-metal
?
Which
properties
of the halogens suggest that they are
non-metals
?
Identify
five

ways
in which chlorine, bromine, and iodine are
similar
.
What are the
formulae
of the
compounds
formed when halogens react with Group 1 metals? What is the
pattern
?
What is the
trend
in the
chemical reactivity
of the
halogens
down the group?
What is the
trend
down the group in the
boiling points
of the
halogens
?
Identify
and
describe

two reactions
which
illustrate
the
trend
.
Starter
Lesson Objectives
A
more reactive

halogen
will always
displace
a
less reactive
hal
ide
from its
compound
in solution.
e.g. Potassium Bromide and Chlorine:
2KBr + Cl 2KCl + Br

Determine if the following reactions will occur.
If they do, write a balanced equation for the reaction.
1) Potassium Iodide + Chlorine
2) Sodium Chloride + Iodine
3) Sodium Iodide + Bromine
4) Potassium Bromide + Iodine
5) Potassium Astatide + Chlorine
2
2

Why?
L10 – Ionic theory
L11 – Using ionic theory to explain the key properties of salts
Aim: To investigate the properties of different salts

Shape
and
colour
Melting point (
high/low
?)
Conductivity of
solid
Solubility
Conductivity of
solution


Groups of 4 – split the different activities between the 4 of you. E.g. 2 people investigate 1 and 2, 2 people investigate 3 and 4.
Complete for at least 2 different salts
Copy and complete as much of the table as you can.
Use the textbook if you need, and recall the video
Properties of Salts
Copy and complete the table, remember to include the name of the salt.

What conclusions can you draw about the
Melting points
of salts?
The
conductivity
of salts?

Write this down as
two
sentences in your book.
To record…
Salt
Halogen
Electron
Atom
Alkali
Metal
Non-metal
Nucleus
C4
Activity AC4.14 Investigating Salts
colourless conduct conducts dissolved
high ions metals move
non-metals
non-metals
ions
colourless
dissolved
conduct
metals
move
high
6 Mark Question
Describe and investigate the key properties of salts
1) Potassium Iodide + Chlorine
2) Sodium Chloride + Iodine
3) Sodium Iodide + Bromine
4) Potassium Bromide + Iodine
5) Potassium Astatide + Chlorine
Answers
Equations
1)
3)
5)
2NaI + Br I + 2NaBr
2
2
2KAt + Cl At + 2KCl
2
2
2KI + Cl I + 2KCl
2
2
Charge
Mass
Relative atomic mass
Proton number
Period
Group
Shell
6 mark question
Compare the
properties
and
appearance
of Sodium and Chlorine with Sodium chloride. (6 marks)
Sodium is ...
a
silvery / metallic
element,
that
conducts electricity
,
OR
with a fairly
high melting point
(solid)
Chorine is ...
a
yellow-green / non-metallic
element,
that
does not conduct electricity
,
OR
with a
low melting point
(gas)
Sodium Chloride is ...
a
white / colourless
compound
,
that
conducts electricity
only

when

molten
or
dissolved
in solution,
OR
with a
very
high melting point
(solid)
1 mark for each point
-
+
The illustration shows
part
of a sodium chloride lattice.
Assign your partner a mark out of 6.
Each point = 1 mark
Peer mark
and
comment using
purple pens
Evidence for ions
Michael Faraday
decided that compounds
decomposed by electrolysis
must contain
electrically-charged particles
.
When they reached the electrodes, the
charged particles turned back into atoms
.
Since
opposite charges attract
each other, he imagined the compound had contained
positive and negative particles
that were attracted to oppositely charged electrodes.
Method
Calcium
Chloride
Chromium Oxide
Potassium
Sulphide
Iron
Bromide
Barium
Oxide
chemical name
Use square brackets
to show electron configurations of ions and
write the charge
as a
superscript
Gained 2
electron so
2-
2
The formula is
Mg
Cl
Short-cut:
'
Crossover
' method
Answers
Can you complete the rest now?
Extension Task
HINT: Treat negative ions as a
single particle
.
Put into brackets
if more than one is needed.
Instructions
Team 1
1. Look at the crystals with a hand lens.
What do you notice about their shape? What colour are the crystals?

2. Place a few grains of the salt in the bottom of a dry test tube. Heat the tube strongly for a few minutes.
Decide whether the salt has a high or low melting point.
3. Test to see if the solid crystals conduct electricity. Add 1 ml of water to a test tube. Add the salt a little at a time.
Is the salt very soluble, soluble, slightly soluble, or insoluble?

4.
If a solution formed in step 4
, pour a little of it into a watch glass, or dish, and
test to see whether or not it conducts electricity
. Remove the electrodes as soon as you have checked whether it conducts or not.
A sodium chloride
crystal
is made up of millions of oppositely charged Na+ and Cl− ions. These are attracted to each other through
electrostatic

forces
, and arranged in a regular pattern called a
lattice
.
Na+ has the same configuration as Neon



Cl- has the same configuration as Argon


Stable ions tend to have the
same configuration as one of the noble gases
atom
attracted
charge
KEYWORDS
Some may be used more than once
gained
lost
opposite
For each compound, write the correct formula
Hydrogen + oxygen water
Complete the WORD equations:
s
=
s
olid,
l
=
l
iquid,
g
=
g
as,
aq
=
aq
ueous solution
Liquids
include
water
and
bromine
Gases
include
hydrogen, oxygen, nitrogen, fluorine, chlorine
The next step is to write down the formula of the reactants and products.
The formula of sodium (and all other metals) is the same as the symbol,
Na
.
The formula for a water molecule is
H O
.
Balancing equations: example
The final step is to balance the equation so that it has the same number of atoms of each element on each side. This can be done by putting the correct numbers in front of the formulae.
Each of the hydroxides of group 1 metals has a formula with the metal symbol and OH for hydroxide. So sodium hydroxide has the formula NaOH.
Hydrogen is an element that exists as diatomic molecules, so its formula is H .
We can now begin to write the symbol equation:
... if the question asks for state symbols, put them into the balanced chemical equation.
For example, in the equation discussed above the state symbols would be inserted as follows:
sodium + water sodium hydroxide + hydrogen
The first step is to write a word equation, showing the reactants and products.
Na + H O NaOH + H
Balancing equations: example
2
2
2
2
2Na + 2H O 2NaOH + H
2
2
Remember...
2Na + 2H O 2NaOH + H
2
2
(s)
(aq)
(g)
(l)
Balancing equations: example
Balancing equations: example
Next write the formula of the reactants and products.
Balancing equations: example
Finally, balance the equation by putting the correct numbers in front of the formulae...
hydrogen + oxygen water
Write a word equation
2
2
2
Write the symbol equation:
H + O H O
2
2
2
2H + O 2H O
2(g)
2(g)
2
.. and include state symbols
(l)
potassium hydroxide + hydrogen
lithium oxide
sodium chloride
Compound
Compound
Compound
Compound
Element
Element
Element
=1
=1
=1
=3
=3
=1
=2
=2
=2
=2
=3
=3
=1
=3
=2
=3
potassium hydroxide
rubidium hydroxide
caesium hydroxide
sodium hydroxide
lithium hydroxide
caesium fluoride
sodium bromide
potassium oxide
lithium chloride
rubidium oxide
lithium iodide
sodium iodide
sodium oxide
rubidium
sodium
lithium
solid
gas
solid or aqueous
solid or aqueous
liquid
solid or aqueous
solid or aqueous
solid or aqueous
solid or aqueous
solid or aqueous
solid or aqueous
solid or aqueous
solid
solid
4
s
2
g
2
s
2
s
2
aq
g
l
2
2
s
g
2
s
2
2
l
s
2
aq
2
g
s
s
s
4
s
g
2
s
2
s
2
aq
g
l
2
2
s
g
2
s
4
s
g
2
s
2
s
g
2
s
c, e, f, j
b, d, g
h, i
2 Li
:
1 O
2-
2
The formula is
Li
O
1 Mg
: 2 Cl
To get an overall charge = 0, we need;
4Na + O 2Na O
2
2
(s)
(s)
(g)
2K + Cl 2KCl
2(g)
2Na + 2H O 2NaOH + H
2
2
(s)
(aq)
(g)
(l)
K + O K O
(s)
2(g)
2
2Li + 2H O 2LiOH + H
2
2
(s)
(aq)
(g)
(l)
(s)
(s)
(s)
100,000 fm (0.1 nm) = 1 Angstrom
Full transcript