The Chemistry of Life
You should know:
 What three subatomic particles make up atoms?
 How are all the isotopes of an element similar?
 What are the two types of chemical bonds?
The Big Idea:
Matter and Energy
 Life depends on chemistry
 Chemistry =
 Matter =
 Chemical reactions keep you
alive
Atom…way smaller than a cell
 Basic unit of matter
 The building blocks of EVERYTHING!
 Your phone, a dog, your lunch, your body, your bed, your
clothes, your car, your house, your pencil!
Democritus, 2500 years ago
 Democritus asked, can you
divide a substance without
limit, or does there come a
point at which you cannot
divide the substance
without changing it into
something else?

Democritus thought
that there had to be a
limit, and he called the
smallest fragment the
atom, from the Greek
word atomos, which
means “unable to be cut.”
Subatomic particles
P
N
E
Protons
Electrons
Neutrons
Element
Mercury, Hg
=
 Elements make up earth & organisms
 cannot be broken down by a chemical
process into a simpler substance
 100+ elements are known, but only about two
dozen are commonly found in living
organisms.
 Ex: Oxygen (O), Nitrogen (N), Carbon (C)
Phosphorus (P), Hydrogen (H)
6
C
Carbon
12.011
Atomic number
Isotope
Nonradioactive carbon-12
6 electrons
6 protons
6 neutrons
Nonradioactive carbon-13
6 electrons
6 protons
7 neutrons
Radioactive carbon-14
6 electrons
6 protons
8 neutrons
Isotopes
 mass number =
 Isotopes are identifiedamed by their mass numbers;
EX: carbon-12, carbon-13, and carbon-14.
6
C
Carbon
12.011
Atomic Mass
The average of the masses of all of an elements
isotopes is called its atomic mass
http://ed.ted.com/lessons/just-how-small-is-an-atom
Isotopes
 Because they have the same number of
electrons, all isotopes of an element have the
same chemical properties.
 Isotopes - have an unstable nucleus that
breaks apart giving off energy in the form of
radiation
Radioactive isotopes
Can be dangerous
Can be used
practically
 Radioactive dating
 Treat cancer
 Kill bacteria
 used to tell age of fossils
 preserve food
Compounds
=
 Often has very different physical and
chemical properties than its elements.
Ex) H2O, 2 H and 1 O, 2:1 ratio
Ex) NaCl, 1Na and 1Cl, 1:1 ratio
Table Salt
Chemical Bonds
 The force that holds atoms together
 Electrons are the key players
 valence electrons =
2 main types of bonds
1) Ionic bonds
2) Covalent bonds
Ionic Bonds
Sodium atom (Na)
Chlorine atom (Cl)
Sodium ion (Na+)
Chloride ion (Cl-)
Protons +11
Electrons -10
Charge
+1
Protons +17
Electrons -18
Charge
-1
Transfer
of electron
Protons +11
Electrons -11
Charge
0
Protons +17
Electrons -17
Charge
0
If an atom loses an electron it
becomes ______________
called a
If an atom gains an electron it
becomes _______________
called a
Covalent Bonds
 Sometimes electrons are shared by atoms instead of
being transferred.
 The moving electrons travel about the nuclei of both
atoms, forming a covalent bond.
Covalent Bonds
 The structure that results when
two or more atoms are joined
together by covalent bonds is
called a molecule, the smallest
unit of most compounds.
 Ex: Each hydrogen atom is
joined to water’s lone oxygen
atom by a single covalent bond.
Each hydrogen atom shares two
electrons with the oxygen atom.
COVALENT VS. IONIC
Van der Waals Forces
A slight attraction that develops
between the oppositely charged
regions of nearby molecules due
to unequal sharing of electrons
New Vocabulary
 Atom
 Electrons
 Protons
 Neutrons
 Valence electrons
 Element
 Ions
 Negative Charged
 Positive Charged
 Isotope
 Mass Number
 Atomic Mass
 Atomic Number
 Compounds
 Molecules
 Covalent Bond
 Ionic Bond
1. Describe the structure of an atom.
2. Why do all isotopes of an element
have the same chemical properties
3. What is a covalent bond?
4. What is a compound? How are they
related to molecules
5. How are ionic bonds and Van der
Waals forces similar? How are they
different?