Chapter 3
Chemistry
3.1 Matter
• Matter – anything that occupies space and has
mass
• Mass is the quantity of matter an object has
• The pull of gravity on an objects mass gives it
weight
• Changes in matter are essential to life’s
processes
Physical Properties of Matter
• Can be observed or measured without permanently
changing the identify of the matter
• Ex. - Color, odor, texture, taste, hardness, melting
point, boiling point
Chemical Properties of Matter
• Describes the ability to
change into a new
substance as a result of a
chemical change
• Ex. Coal burning – can
not get it back
3.2 Atoms
• Fundamental unit of matter (atom)
• Atoms are the basic building blocks of matter
• Cannot be subdivided further by any ordinary
chemical means
• Made up of subatomic particles (P, N, E)
• Have a net zero charge
Structure of Atoms
• Nucleus – small central
part – made of protons
and neutrons
• Protons – positively
charged particles
• Neutrons – neutral
particles
• Electrons – negatively
charged particles found in
the space outside the
nucleus
The Nucleus
• Atomic number – the number of protons in the
nucleus determines the atomic number of an
element
• Each atom has it’s own atomic number
• Most of the mass of an atom lies in its nucleus
• Mass number – the mass of the entire atom is equal to
the sum of its protons and neutrons
• Mass number – atomic number = # of N
• Atomic Mass – the average mass of all of the atoms of
a particular element
Electrons
• Atoms generally have the
same number of protons
and electrons
• Atoms are electrically
neutral in normal
circumstances
• Electrons determine the
chemical properties of
atoms
• Electrons are arranged in
levels – energy levels
Energy Levels
• Each energy level is a different distance from the
nucleus
• The first energy level holds 2 e• The second energy level holds 8 e-
• A filled outer energy level is a stable electron
arrangement
• Atoms with unfilled energy levels (valence
shells) tend to form compounds where each
atom has a filled outer level
• Gain, lose or share
• First Energy Level: 2
Second Energy Level: 8
Third Energy Level: 18
Fourth Energy Level: 18
Fifth Energy Level: 8
Elements
• Made of only one type of
atom
• Cannot be broken down
into simpler substances
• Ex. O2, Fe2
Compounds
• Made when two or more
kinds of atoms are
combined in definite
proportions
• Differs in physical and
chemical properties from
the elements that
compose it
• Can be separated into the
elements that make them
up
• Ex. CO2, H2O
Chemical Formula
• Shows the kind and proportion of atoms that
form a particular compound
• Ex. CO2, H2O
Structural Formula
• Shows the number and
kind of atoms in a
molecule but also how
the atoms are bonded to
one another
Isotopes
• Varieties of an element that differ only in the
number of neutrons
• Not exactly alike but they behave the same way
chemically – same number of e• Ex. Hydrogen – Protium, Deuterium, Tritium
Radioactive Isotopes
• The nuclei of many isotopes are unstable
• Radioactivity – unstable nuclei give off (emit)
charged particles and radiation
• Loss of particles (protons) changes the particle
to different isotopes, usually of a different
element
Practical Uses of Radioactive
Isotopes
• Tracer – can follow the isotope through stages in
a chemical reaction
–
–
–
–
–
Ex. P-32 – plants
I – 131 – Thyroid gland
Fe – 59 – blood circulation
Cobalt 60 – used to kill cancer cells
Carbon 14 – brain tumor
• Kill bacteria that cause food to spoil
• Measure the age of certain rocks
• Must be careful – radiation can kill
3-3 Interactions of Matter
• Chemical bonding – combining of atoms of
elements
• Atoms follow rules
• Rules are based on the number of e- in the outer
energy level
Ionic Bonds
• Transfer of e- from one atom to
another
• Caused from the gain or loss of
electrons
• Ion – charged particle
Na+ Cl• Formed when an ionic bond
occurs
• Ex. NaCl
Covalent Bonds
• Sharing of e• Shared e- are in the outer most level of both
atoms at the same time
• Strong bond
• Single, double or triple
• Ex. CO2, H2O, Br2, F2
• H-H, O=O, N N
Molecule
• Formed when 2 or more
atoms join together in a
covalent bond
• Ex. CO2, H2O, NH3,
C6H12O6
• Regardless of the type of bond formed atoms
change their physical and chemical properties when
they form a compound
Ex. Na – silvery metal, reacts explosively with
water
Cl – poisonous greenish gas – WWI
NaCl – table salt – solid- dissolves in water –
not poisonous
3.4 Chemical Reaction
Reactants  products
AgNO3 and NaCl  AgCl3(s) + NaNO3
Hydrogen Gas Reacting with Oxygen
Chemical Equation
O2 + 2H2 (yields) 2H2O
2H2O  O2 +2H2
(Does not happen. Why?)
Balancing Equations
• Chemists have learned
that the most important
factor in determining
whether a reaction will
occur is the flow of
energy.
• Spontaneous reactions
release energy.
The End