“…beneath the clothes, we find a man... and beneath
the man we find... his... nucleus.”-Nacho Libre
Reference Text - Modern Biology
Chapter 2 / pgs. 30-42
All organisms are made of matter.
 The structure and function of all living
things are governed by the laws of
chemistry.
 Matter is constantly being rearranged
through chemical reactions.
 Chemical structures and reactions are
central to all biological processes.

What do living and non-living have in
common?
All things are made up of matter.

Matter-anything that takes up space and has
mass (solids, liquids, gas, plasma).
◦ Mass – the amount matter an object has.
Chemical
Changes in
matter are
essential to
ALL life
processes.
Matter is made of tiny little particles called
ATOMS !
You cannot see atoms because they are so small.
Lots of atoms join together to make up matter
that you can see.
Nucleus - central core of the atom, consisting
of:
◦ Protons (+ charge)
◦ Neutrons (neutral or no charge).
 Electrons (- charge) are found moving very fast
around the nucleus in orbitals (electron
cloud/energy levels).

Atoms with no charge (neutral) have equal
protons and electrons.
Neutrons
Electrons
Protons
Properties of atoms determine the structure
and properties of the matter they compose.
Charge
Mass
Protons (in Neutrons
nucleus)
(in
nucleus)
Positive
Neutral
(+)
(no
charge)
Big
Big
Electrons
NEGATIVE
(-)
VERY
small
DRAW A PICTURE OF AN ATOM
(LABEL ALL THE PARTS)
Atoms can join together in different ways to
make different kinds of matter.
Some matter has only one kind of atom.
This is called an ELEMENT.
An element is:
 A pure substance that cannot be broken down
chemically into simpler kinds of matter.
Elements are
arranged on
THE
PERIODIC
TABLE.
The table
provides
information
such as
chemical
symbol,
atomic number
and atomic
mass for each
element.
How to Read the “Periodic Table”
Each element has unique chemical symbol
Atomic Number - # of
protons in an atom (also
tells the # of electrons).
Atomic Mass # - number
of protons + number of
NEUTRONS
FYI - if you are talking about average atomic mass, which
is shown on the periodic table, it is the sum of the
masses of the common isotopes of an element.
There are more than 100 elements, but only
about 30 are important to living things:
6 Major elements:
 Carbon – 18.5%
 Hydrogen – 9.5%
 Oxygen – 65%
 Nitrogen – 3.3%
◦ Phosphorus – 1.0%
◦ Sulfur – 0.3%
 Others - K, Ca, Na, Fe
(trace elements)
Approximately
95% of the
mass of living
things is made
up of these
four elements
Under normal conditions, most elements do not
exist by themselves…
 A compound is a pure substance made up of
atoms of 2 or more elements chemically joined,
making them more stable
Examples: CO2,H2O2, H2O
 A molecule is the simplest part of a substance
- 2 or more atoms chemically
joined together.
Examples: H2O, O2, CO2,
H2O2, H2
1. Share electrons
Covalent Bond
2. Steal electrons
Ionic Bond
Salt- the outer electron of Na atom is
transferred to the Cl atom
~this results in ions - an atom with a + or –
charge.
Because + and – attract, this attraction is
called an ionic bond.
Atom of Oxygen
Molecules of Oxygen
Compound containing Oxygen