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The Chemistry of Biology

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Sonia Bawa

on 2 September 2016

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Transcript of The Chemistry of Biology

The Chemistry of Biology
Do Now
What is matter?

What is it made of?

In what forms can we find matter?

Why is matter of importance to us?
Elements in Living Organisms
Matter
Anything that has mass and takes up space
3 States of Matter
Atoms
Building blocks of matter
There are different atoms for different pure substances.
These pure substances are called...
ELEMENTS
+
Label the Atom
"Opposites attract"
Structure of atom due to
attractions
between protons and electrons
+
_
Elements cannot be broken down into other substances
Rows = periods
O
xygen,
C
arbon,
H
ydrogen, and
N
itrogen make up 96.3% of humans.
Elements
Atomic Number
Chemical Symbol
Chemical Name
Atomic Mass
(Based on # of protons)
An atom of a certain element always has the
same
number of...
HOWEVER, some atoms of elements can have different numbers of
neutrons
, which changes...
PROTONS
ATOMIC MASS
Atoms of the
same
element that have
different
numbers of
neutrons
are called...
ISOTOPES
Isotopes
Same # of...
PROTONS
Different # of...
NEUTRONS
Radioactive Isotopes
Does adding neutrons increase atomic mass? Charge?
Sometimes, if the nucleus has
too many neutrons
(it gets too heavy), the nucleus becomes
unstable
.
Radioactive Decay
The nucleus starts to
break apart
(decay) to get to a more
stable
state.
As the nucleus breaks apart, it emits
RADIATION
Why is this important?
What happens when you combine 2 or more different elements to form a pure substance?
COMPOUNDS
Table Salt
Water
Compounds
Specific combination of elements in a
fixed ratio
E.g. Sodium Chloride Salt is always formed from 1 sodium (Na+) atom and 1 chlorine (Cl-) atom
Physically different from elements that comprise them.
E.g. Sodium Chloride Salt is
chemically and physically different
from pure sodium atom and pure chlorine
Compounds
Compounds
Cannot be broken down by physical means
E.g. You cannot break water apart by tearing it. You will never pull the Hydrogen atoms and the Oxygen atom apart.
Compounds can only be chemically separated.
Lets go back to the
ATOM
Protons
and
neutrons

are the components of the atom that have
MASS
The mass of each is approximately
1 g/mol
No matter what state
matter
is in...
The atoms and molecules are
hard
and
dry
Protons
,
neutrons
, and
electrons
are called...
Subatomic Particles
Compound
substances are made of many of the same
molecule
Water is made of many
H2O
molecules
How are
compounds
formed?

CHEMICAL BONDS
Forces that hold substances together
ONLY IF...
the atoms are held together by
covalent bonds
In an atom, what can change?
Electrons
Energy Levels/Shells
Valence Electron(s)
Electrons in the outermost shell
Partially filled shells are
UNSTABLE
.

CHEMICAL BOND FORMATION
Two Types of Chemical Bonds
Covalent Bonds
Ionic Bonds
Covalent Bonds
2 atoms share their valence electrons
In other words
A
molecule
is a compound whose atoms are held together by covalent bonds.
Most of the compounds that comprise living organisms are
covalently bonded
IONS
1 pair of electrons is shared
2 pairs of electrons are shared
3 pairs of electrons are shared
SINGLE BOND
DOUBLE BOND
TRIPLE BOND
What kinds of bonds does a water molecule have?
One way atoms can become stable is by
accepting
or
donating
electrons.
When an atom accepts or donates an electron, it becomes
CHARGED
, making it an
ION
.
Which atoms are more likely to donate electrons?
Which atoms are more likely to accept electrons?
Atoms that
donate
electrons _____________ their outer electron shell.
Atoms that
accept
electrons ___________ their outer electron shell.
Ions with a (+) charge
Ions with a
(-) charge
CATIONS
ANIONS
To get a
cation
, an atom must have _______________ electrons.
To get an
anion
, an atom must have _______________ electrons.
Ionic Bonds
"Opposites Attract"
Ions are held together by an
electrical attraction
between opposite charges.
Now we have looked at what holds two atoms together, but
what holds molecules together
?
Which atoms/elements are the most stable? Why?
van der Waals forces
Remember electrons are
randomly
moving around the nucleus of an atom
Sometimes
one area
will have
more
______________ than another,
at this moment
, the side with more electrons will have a
more
_________________
charge
than the other side.
intermolecular forces
This side will be considered temporarily _______________ and the other side will be temporarily __________________.
Then, the temporarily ______________ side of one molecule will be attracted to the temporarily _______________ side of another molecule
These attractions are called __________________________________________, and these forces hold ______________________ together.
Na+
Cl-
K+
Determining the
age
of rocks or fossils by radioactive
carbon dating
Studying activity within an organism via
“tracers”
van der Waals forces are very weak intermolecular attractions
Recall
Covalent bonds are formed when 2 atoms _______________________________.
When electrons are evenly shared, the molecule formed is ___________________.
When electrons are unevenly shared, the molecule formed is ____________________.
In a polar molecule, electrons are ______________ shared.
This means one side of the molecule is ______________________ and the other side is _________________________.
How are polar molecules different from other molecules that experience van der Walls forces?
The partially _______ end of a molecule attracts to the partially _______ end of a different molecule
Then what?
This forms a...
Weak electrostatic attraction
Polar Molecule
Partially negative charge
Partially positive charge
Water
When a polar molecule involves a Hydrogen atom and either a Fluorine, Oxygen, or a Nitrogen atom, the _____________________ attractions are called ___________________________.
Hydrogen bonds are
necessary
for the existence of life
They are hold
DNA
and
proteins
together!
Why are hydrogen bonds weaker than ionic bonds?
To become
STABLE
, atoms:
Gain/lose
electrons
Attract
valence electrons from another atom

The mass of electrons is considered to be
negligible

Protons =
Neutrons =
Electrons =
Water
's life-sustaining properties are due to its
polarity
and ability to form
hydrogen bonds
.
Ice is less dense thank liquid water because…

Hydrogen bonds
hold water molecules further apart in ice
This is why ice floats in water

Unique Properties of Water
hydrogen bond
Ice
Hydrogen bonds are stable

Columns = groups
LOST
GAINED
Atoms with few (1-2) valence electrons
Atoms with more (6-7) valence electrons
EMPTY
FILL
share electrons
nonpolar
polar
unevenly
more positive
more negative
(+)
(-)
Hydrogen bonds
weak electrostatic
Full transcript