
Everything in the universe is made up of
matter.
› Matter- anything occupying space and has
mass.
 Mass- amount of matter an object has.
 Weight- force of gravity on a given mass.
Q: Would your weight or mass change if you
went to the moon?

Elements- pure substances that cannot
be broken down chemically into simpler
kinds of matter.
› 100+ elements have been discovered.
› Less than 30 are important to living things.
› Over 90% of the mass of living things consists
of:




Carbon (C)
Hydrogen (H)
Oxygen (O)
Nitrogen (N)

Periodic Table of Elements- lists
information about each element
including the element’s
› Chemical symbol- 1-3 letters
› Atomic number
› Atomic mass

Atom- simplest particle of an element
that retains all of the properties of that
element.
Nucleus

3 Subatomic Particles in Atoms
› Proton- Positively charged particle found in
the atom’s nucleus. ATOMS OF AN ELEMENT
ALWAYS HAVE THE SAME NUMBER OF
PROTONS.
› Neutron- Found within the nucleus and has
no charge.
› Electron- Small negatively charged particles
with very little mass.
 Move in orbitals found outside of the nucleus.

Nucleus
› Most of the atom’s mass
› Contains protons and neutrons
Atomic Number = # of protons
 Mass Number = # of protons + # of neutrons

Q: How can you determine the number of
neutrons an atom has?
A: Mass number – Atomic number = # of neutrons

Atoms have a net charge of ZERO.
› # of Protons (+) = # of electrons (-)

Orbital- 3D region around the nucleus
indicating the probable location of an
electron.
› Combination of all orbitals  electron cloud
› Farther from nucleus  greater electron’s energy

Orbitals and energy levels:
› Each energy level corresponds to certain
orbitals that can hold a set number of
electrons.
 First energy level has 1 orbital- holds maximum
of 2
 Second energy level has 4 orbitals that hold 2
electrons each (total of 8).

Isotopes- Atoms of the same element
that have a different number of neutrons
(number of protons DOES NOT change).
› Changes atomic mass

http://gtmmedia.discoveryeducation.com/videos/
Discovering the
Elements/sec2941_300k.asf

Atoms of most elements readily combine
with the same/different atoms or
elements to make compounds.

Compound- atoms of 2+ elements in
fixed proportions.
› Ex: Water (H2O)
Chemical and physical properties differ
between compounds and the elements
making them up.
 Number and arrangement of edetermines how elements combine and
form compounds.

› Atoms are stable/less reactive when highest
energy level is full. Ex: Noble gases

Attractive forces holding atoms
together.
› Covalent Bond
› Ionic Bond
› Hydrogen bond

Formed when 2 atoms SHARE 1+ pairs of
valence electrons.

Transfer of e- from a metal atom to a
nonmetal atom.
› More stability for the atoms involved.
› Creates ions (charged atoms that have
gained/lost e-)
HCl
2. CO2
3. Cl
4. Li
5. H2O
1.
HCl, CO2, and H2O- compounds
Cl and Li- elements
Energy- the ability to do work.
 Forms of energy include:

› Radiant (light) energy
› Thermal (heat) energy
› Chemical energy
› Electrical energy
› Mechanical energy
All atoms and molecules in a substance
are in constant motion.
 Motion of and spacing between
atoms/molecules determine the
substances state:

› Solid
› Liquid
› Gas
Move less rapidly than liquids or gases
 Fixed volume
 Molecules/atoms more closely linked
than liquids or gases (with the exception
of H2O).


Maintain a fixed volume, but particles
move more freely  ability to flow and
conform to container’s shape.
Particles move rapidly
 Little to no attraction to each other.
 Fill the volume of the container they
occupy.


Chemical Reaction- change from one
substance to another.
› Energy is absorbed/released when bonds
are broken and new bonds are formed.
› Ex: CO2 + H2O  H2CO3 (see pg 36 Fig 2-6)
Q: Where are the reactants? Products?
Q: What does the arrow represent?
Reactants  Products
 Products  Reactants
 Number of each type of atom must be
EQUAL on both sides of the equation.
 Reversible reactions shown using arrows
pointing in both directions.


Sugars, proteins, and fats in your food
get broken down into CO2, H2O, and
other products.
› Breaking bonds  release of energy to be
used in building & maintaining cells, tissues,
and organs.

Activation energy- amount of energy
needed to start a reaction.
› Usually a large amount of energy is needed
to start reactions.

Catalysts- reduce the activation energy
needed for a reaction without being
changed/destroyed.
› Enzymes- “special” proteins
› RNA molecules

Oxidation-reduction reaction = redox
› Oxidation reaction: reactant loses 1+
electrons  more + charge
› Reduction reaction: reactant gains 1+
electrons  more – charge
› Oxidation reactions are always followed by
a reduction reaction.

Forming Na+ Cl- involves oxidation and
reduction reactions.
› Na donates an e- to Cl  oxidation of Na to
form Na+
› Cl accepts an e-  reduction of Cl to form
Cl-
Type of protein.
 Most enzyme reactions are reversible
(arrow goes both ways).
 Maintain homeostasis: reactions would
not occur fast enough without them.
 “–ase” = enzyme
 ONLY react with specific substrates.
