Download Chapter 3: Atoms and Moles By: John Pierce

CHAPTER 3: ATOMS AND MOLES
By: John Pierce
SECTION 1: SUBSTANCES ARE MADE OF
ATOMS
The law of definite proportions states that two of
the same substances that have different sizes
have the same proportions by mass.
 The law of conservation of mass states that mass
can’t be formed or destroyed in normal chemical
and physical changes. This law also states that
the mass of the reactants in a equation equals
the mass of the products.
 The law of multiple proportions states that when
two elements merge to create two or more
compounds, the mass of one element that
combines with a given mass of the other is in the
ratio of small whole numbers.

SECTION 1: SUBSTANCES ARE MADE OF
ATOMS

Dalton’s Atomic Theory States
1.
2.
3.
4.
5.
All matter is made up of atoms, which can’t be
divided, created, or destroyed
Atoms of a given element are identical in their
physical and chemical properties.
Atoms of different elements differ in their physical
and chemical properties.
Atoms of different elements to combine in simple,
whole-number ratios to form compounds.
In chemical reactions, atoms are combined,
separated, or rearranged but never created,
destroyed ,or changed.
SECTION 2: STRUCTURE
OF
ATOMS
The diagram to
the left shows the
parts of an atom.
The nucleus is the
center of the atom
and houses the
protons and
neutrons. Protons
have a positive
charge whereas
neutrons have a
neutral charge.
Shown in the
outer field of the
nucleus is the
electron cloud,
where electrons
constantly move.
Electrons have a
negative charge.
SECTION 2: STRUCTURE
The picture to the
left shows
uranium isotopes.
Isotopes are atoms
of the same
element that have
different numbers
of neutrons.
OF
ATOMS
SECTION 3: ELECTRON CONFIGURATION
Shown on the top
are the shapes and
orientations of the
s and p orbitals,
on the bottom are
the different
shapes and
orientations for
the d orbital. Each
orbital that is
shown can hold a
maximum of two
electrons.
SECTION 4: COUNTING ATOMS
The mass of atoms are expressed in Atomic mass
Units or AMU.
 A mole is defined as the number of atoms in
exactly 12 grams of carbon- 12.
 The number of particles present in 1 mole of a
substance called Avogadro’s number
(6.0221367 X 1023)

WORK CITED

Meyers, R. Thomas, et al. Ch 3, Pages 74-104
Holt Chemistry Austin, TX: Riehart and
Winston, 2004.