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Inside the Atom

http://www.australiancurriculum.edu.au/Elements/ACSSU177
by

Gerald Carey

on 27 February 2015

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Transcript of Inside the Atom

The Atom
The Australian Curriculum for Year 9 Science:
"All matter is made of atoms which are composed of protons, neutrons and electrons; natural radioactivity arises from the decay of nuclei in atoms"
Content descriptor (ACSSU177) http://www.australiancurriculum.edu.au/Science/Curriculum/F-10#level=9
Inside Atoms
Atoms:
are the building blocks of the universe
are microscopic
exist in 118 known types
are organised in the
periodic table

98% of the known universe is made up of two elements - Hydrogen and Helium
Two or more different atoms
Two or more atoms of the same type
Compound
Element
0
2
Oxygen
(Gas)
C
Carbon
(Diamond)
Au
Gold
(Metal)
For example:
Molecule
Lattice
Combinations of different atoms
Combinations of different atoms in repeating patterns
As either
Water
H
H
0
H O
2
Sodium Chloride
NaCl
Sub-atomic structures
Electron
Negative charge
Proton
Positive charge
Neutron
No charge
Determines the type of atom.
Number of
protons
= atomic number
Atomic number of Carbon = 6.
Therefore it has 6
protons
Atomic mass
Number of
protons
plus the number of
neutrons
= atomic mass
Atomic mass of Carbon = 12.
It has
6 protons
and

6 neutrons
Electrons are found at discrete distances from the nucleus.
They surround the nucleus in
electron shells
like onion layers.
This is the first electron shell.
It is filled first but can only have a maximum of two electrons.
This is the second electron shell.
It is filled next but can only have a maximum of eight electrons.
Ions
Sodium atom
Chlorine atom
11P
11N
17P
18N
(Gas)
(Metal)
17 protons = 17 electrons
Therefore it is a neutral atom
11 protons = 11 electrons
Therefore it is a neutral atom
Add
sodium metal
to
chlorine gas
and a
chemical reaction
occurs
Sodium

"donates"
an electron to
chlorine
Sodium ion
Chloride ion
11P
11N
17P
18N
17 protons = 18 electrons
Therefore it has a negative charge
11 protons = 10 electrons
Therefore it has a positive charge
Sodium Chloride
11P
11N
17P
18N
(White solid)
A
bond
has formed between these two atoms.
Because the
bond
has formed between two ions, it is called an
ionic bond
.
Sodium
ion
has one
less
electron than protons
therefore it is
positively
charged
it is called an '
ion
', specifically a
cation
symbol is:
Na
+
Chloride
ion
has one
more
electron than protons
therefore it is
negatively
charged
it is called an '
ion
', specifically a
anion
symbol is:
Cl
-
Sodium chloride does not exist as two atoms joined together in isolation.
It exists as a lattice of repeating sodium and chloride ions
Note that the total number of protons (28) = total number of electrons (28).
So Sodium Chloride has no overall charge!
Such ionic compounds are:
brittle
strong
hard to 'melt'
Add it to water
The lattice starts to break up
This forms an '
ionic solution
' because the ions are now free to move about.
This solution also conducts electricity very well!
Nuclear Decay and Radiation
11P
11N
What's the difference between a chemical reaction and a nuclear reaction?
In a
chemical reaction
, atoms gain or lose electrons e.g.
Sodium
loses an electron if it reacts with
Chlorine
.
11P
11N
Sodium
ion Na
+
In a
nuclear reaction
, atoms can gain or lose neutrons or even protons e.g.
Sodium

sometimes
loses an proton to become Neon.
10P
11N
High energy particle is lost
Electron is lost
Chemical v Nuclear reactions
Isotopes
6P
6N
Most atoms are stable.
Generally they do
not
undergo nuclear decay.
If these nuclear reactions occur naturally it is called
nuclear decay
.
This is 'normal
carbon.
It is:
stable
sometimes called
carbon-12
.
99% of the carbon in the world exists in this form
6P
7N
This is
carbon-13
. It is:
stable
an
isotope
of carbon.
(Why?)
1% of the carbon in the world exists in this form
6P
8N
This is
carbon-14
It is:
un
stable
an
isotope
of carbon.
(Why?)
very little the carbon in the world exists in this form
Isotopes of carbon
}
}
Radioactive isotope of carbon
Isotopes of other atoms exist
For example: Hydrogen
1P
0N
Hydrogen-1
'Normal'
1P
1N
Hydrogen-2
Not radioactive
1P
2N
Hydrogen-3
Radioactive
92P
146N
Types of Nuclear Decay
Uranium-238
90P
144N
Thorium
alpha
particle
Alpha decay
2N
2P
= Helium atom
Alpha decay
occurs in 'heavy atoms' with atomic mass greater than 100.
radiation is quickly absorbed by the environment
very little biological damage
6P
8N
Carbon-14
Nitrogen-14
Beta decay
e
Beta decay
occurs when there are more neutrons than protons.
Beta particles can penetrate further than alpha particles
can cause radiation burns
Unstable
Beta
Particle
-
N P
Stable
7P
7N
Neutron changes to a proton
19P
21N
Potassium-40
Potassium-40
Gamma decay
Gamma Decay
can pass through most objects.
can also come from lightning and space
very dangerous to cells and can damage DNA
Can cause cancer
High Energy
Particle
19P
21N
Half life
Measure of radioactive decay
It is the length of time it takes for
half
of some radioactive material to decay.
Iodine-131
Carbon-14
Uranium-238
8 days
5730 years
4.5 billion years
A long time to stay radioactive!
Uses of Radiation
Nuclear imaging of human body
Sterilization of medical equipment, food
Smoke detectors
e-
P
N
Sodium atom
Sometimes these atoms
gain or lose a neutron
. These forms of the atom are called
isotopes
.
Half life of
Half life of
Half life of
Nice summary of subatomic particles
Some revision and more information about isotopes
Musical summary of nuclear decay
Radiotherapy for cancer
Make a
Make an
In school, we only need to be concerned about the first four shells - named:
K - the first shell,
L - the second shell,
M - the third shell and
N - the fourth shell
Look up "Basic Atomic Structure" in YouTube if the link is not working.
If the link does not work, look up "Chemistry Music Video 8: Natural Decay" on YouTube
How much radiation is dangerous?
Really nice revision site:
http://resources.schoolscience.co.uk/stfc/14-16/index.html
(Google "A World of Atoms")

Covers just about everything in this Prezi and has interactive quiz questions on each page.
Interactive site: summary and quiz.
http://resources.schoolscience.co.uk/ICI/11-14/materials/match4pg1.html
A 'real' picture inside a hydrogen atom showing the first electron shell (outer ring) and the single proton in the nucleus (the yellow/red object in the middle).
Nice summary of nuclear decay
http://www.bbc.co.uk/schools/gcsebitesize/science/aqa_pre_2011/radiation/radioactiveact.shtml
Cl
17
35
Na
11
22
A video showing a platinum nanoparticle made up of thousands of individual platinum atoms.
Summary and demonstration of how small an atom is.
Full transcript