Atomic Structure and the
Periodic Table
Chapter 5
Chapter 5
I. The Structure of the Atom
A. Three particles make up the
structure of atoms:
1) protons …. positive charge (+)
2) neutrons … no charge (neutral)
3) electrons …negative charge (-)
B. These particles are located in one of
two locations:
1) in the nucleus – protons and neutrons
2) around the nucleus - electrons
C. The mass of an atom is concentrated in
the nucleus …
Atomic mass = sum of protons + neutrons
D. The Periodic Table indicates the
number of protons in each element:
Atomic number = number of protons
* The atomic number identifies the
element
E. Shorthand notation is used to indicate
the element, atomic number and atomic
mass:
At . Mass
Symbol
At .#
1
1
H
12
6
C
23
11
Na
Hydrogen
1 proton
0 neutrons
Carbon
6 protons
6 neutrons
Sodium
11 proton
12 neutrons
Hydrogen-1
Carbon-12
Sodium-23
Practice: Indicate the name, number of
protons and number of neutrons
17
8
O
56
?
Fe
80
35
Br
64
29
?
201
80
Hg
79
35
?
II. Isotopes
A. “Atoms of the same element
that have different atomic
masses because they have
different numbers of neutrons”
B. The atomic number identifies the
element…
C. The atomic mass = sum of protons +
neutrons
D. Only neutrons can change the atomic
mass
Examples:
20
10
Ne
Neon
10 proton
10 neutrons
21
10
Ne
Neon
10 proton
11 neutrons
22
10
Ne
Neon
10 proton
12 neutrons
20
10
Ne
90.48%
21
10
Ne
0.27%
22
10
Ne
9.25%
What would be the atomic mass of neon?
20 x .9048 = 18.10
21 x 0.0027 = 0.06
22 x 0.0925 = 2.04
20.20
III. Electrons
A. A NEUTRAL atom has the same
number of electrons as protons
B. ION – an atom that has a charge
because it has lost or gained
electrons
IV. The Periodic Table
A. The periodic table is arranged in
specific rows and columns according
to their chemical behavior
B. Specific regions have been
named:
Representative
Group
Period
Noble
Metals
Gases
Non
metals