Atoms and Their Interactions
6.1
Elements
• Elements
– A substance that can not be broken down into
simpler chemical substances
– The Periodic Table lists all known elements
Atoms: The Building Blocks of
Elements
• Atom
– Smallest particle of an element that has the
characteristics of that element
• Structure of an Atom
– Nucleus
• Protons (Positive)
• Neutrons (Neutral)
– Energy levels
(outside of the nucleus)
• Electrons (Negative)
How come atoms do NOT
have a charge?
 In an atom, the number of electrons equals
the number of protons.
 So the number of positive and negative
charges balance out, giving the atom a charge
of 0.
Fill in the following chart:
Particle
Location
Charge
Symbol
negative
e-
Electron
outside of nucleus
In energy levels
Inside the nucleus
positive
p+
Inside the nucleus
neutral
n0
Proton
Neutron
Energy Levels
• First energy level
– 2 electrons
• Second energy level
– 8 electrons
• Third energy level
– 18 electrons
Rules for filling in energy levels!
• The first energy level has to be FULL before electrons
can go into the 2nd energy level
• The 1st and the 2nd energy level has to be FULL before
electrons can go into the 3rd energy level
Compounds
• Compounds are substances made of 2 or more
elements that form a molecule (2 or more
atoms together).
• Examples of common compounds:
– Table Salt - NaCl
– Oxygen gas – O2
– Water – H2O
Properties of Compounds
• Compounds have BONDS between the atoms
• It is difficult to separate the parts of a compound
• Compounds have chemical formulas to tell you what
elements are found in the compound and how many
atoms of each element are present.
– The chemical formula for water is H2O. There are two atoms
of hydrogen and one of oxygen.
Ionic Vs. Covalent Bonds
Ionic Bonds
• Form when electrons
are exchanged between
atoms.
Covalent Bonds
• Form when electrons
are shared between
atoms.
Both types of bonds result in all atoms having a full
outer energy level.
Chemical Reactions
• Chemical reactions happen when bonds are
formed or broken and recombine to form new
compounds
• All chemical reactions that occur within an
organism are referred to as that organism’s
metabolism.
Mixtures
• Mixtures are combinations of 2 or more pure
substances or compounds
• Some common mixtures:
– Iced Tea
– Dirt
– Paint
Properties of Mixtures
• There are NO BONDS holding mixtures
together
• Mixtures can often be separated
• Mixtures can occur in any proportions and DO
NOT HAVE A SET FORMULA and can use
different components
Solutions
Solution – mixture of one or more substances
uniformly distributed in another substance.
Can be solid, liquid, gas
ex. Plasma (liquid)
brass (solid) copper and zinc
soda (liquid/gas) water and CO2
Acids & Bases
The Homeostasis of living things depends on the
degree of acidity (acid) and alkalinity (base) in
certain areas
Acids & Bases
Acids= any substance that forms hydrogen (H+)
in water.
Alkalinity (a/k/a basic solution)= any substance
that forms hydroxide ions (OH-) in water
Acids
- pH < 7
- Sour taste
- Corrosive on metals
- Burns skin
• Ex. Orange juice,
• vinegar, sulfuric acid
*Homeostasis relevance
- your stomach must have a certain acidity
to function properly
Bases
-pH > 7
- Tastes bitter
- Slippery
- Irritate the skin
- Ex. NaOH
- Homeostasis relevance- your small intestine needs a
certain alkalinity (basic) to
function properly
pH Scale
- Tells you how acidic or
basic something is
- Ranges 0-14
- 7 = neutral
- above 7 = base
- below 7 = acid
- Ten fold system
- Measure pH with litmus
paper