Atoms and
Molecules
Unit 4A
The Building Blocks
of Matter
All matter is
formed by:
•Atoms
•Molecules
•Molecules are groups
of different types of
atoms bonded
together.
Subatomic Particles
(Parts of an Atom)
•Proton
•Electron
•Neutron
• Measured by AMU’s
•Atomic Mass Unit
Parts of an Atom
Particle
Location Charge
Mass
+
P
Nucleus
+
1 amu
e
Outside
-
0 amu
0
N
Nucleus
0
1 amu
Parts of an Atom
• Atoms are mostly empty
space.
Ex: If you put a golf ball in
the middle of a football
stadium (nucleus), the
electrons would be WAY
up in the nosebleed
sections.
Atomic Models
• The current model is Electron
Cloud, but it is complicated.
So…
• We will be using the Bohr Model.
The Bohr Model
•Electrons
surround
the nucleus
e
in different
energy
e
levels.
e-
ee-
-
e-
P+ N0
-
e-
ee-
e-
Elements
•Elements = only 1 kind of
atom
•The # of PROTONS in that
element tell us which
element it is
•Listed on P.T. as atomic
number
• The Atomic Number
tells us the number of
Protons an atom has
• It also tells us how
many electrons a
neutral atom has
• REMEMBER - APE
Isotopes
• Isotopes – elements that
have the same # of
protons and a different #
of neutrons
• Isotopes have different
masses.
Atomic Mass
• Mass number = the mass of
one atom
• Atomic mass = the average
mass of all isotopes of that
element.
Mass # =
+
#P
+
0
#N
Isotope Notation
Mass #
12
13
14
6
6
6
C
C
C
Atomic #