- Protons, neutrons, and electrons are the three main subatomic particles that make up atoms. Protons have a positive charge, electrons have a negative charge, and neutrons have no charge. - The periodic table contains information about each element, including the element symbol, name, atomic number, and atomic mass. The atomic number is the number of protons in an atom's nucleus, while the atomic mass takes into account the total number of protons and neutrons. - Electrons are not counted in the atomic mass because they are much smaller than protons and neutrons, and have a negligible contribution to the overall mass of the atom.

1. Do Now Dec 22
- Explain the difference between a
proton, an electron and a neutron.

2. The Periodic Table Elements
• Boxes in the periodic table contain a lot of
information. To understand this information, it is
necessary to refer to the periodic table’s key
Atomic Number
Element Symbol (a capital
letter or a capital followed
by a lower case letter)
Atomic Mass
8
O
Oxygen
15.999
Element Name

3. Atomic Number
• Atomic number- the number of protons in the nucleus of an
atom
• Equal to the number of electrons to make an atom neutral
+
++
-
-
-
What would
be the atomic
number of this
atom?

4. Atomic Mass
• Atomic mass- the total number of protons and
neutrons in an atom’s nucleus
• Expressed in Atomic Mass Units (amu)
• Each proton or neutron has a mass of 1 amu
+
++
-
-
-
What would be the atomic
mass of this atom?
+  3
 4
3 protons + 4 neutrons =
an atomic mass of 7 amu
Why did we not account for the
electrons when calculating the
atomic mass?

5. Atomic Mass
• Atomic mass- the total number of protons and
neutrons in an atom’s nucleus
• Expressed in Atomic Mass Units (amu)
• Each proton or neutron has a mass of 1 amu
+
++
-
-
-
What would be the atomic
mass of this atom?
+  3
 4
3 protons + 4 neutrons =
an atomic mass of 7 amu
Why did we not account for the
electrons when calculating the
atomic mass?

6. Sub-atomic Particles
Size Comparison
(protons, neutrons, electrons, & quarks)
Size in
atoms
Size in
meters
(m)
Atom 1 10-10
Nucleus __1__
10,000
10-14
Proton or
Neutron
___1___
100,000
10-15
Electron
or Quark
_____1____
100,000,000
10-18
(at largest)
+
+
+
+
+
++
-
-
-
-
--
-
-
+

7. Stations
• 1. Students will be able to calculate the atomic
mass unit in order to determine atomic mass
unit. Complete math section in textbook on
page 93.
• 2. Students will be able to infer information
about electromagnetic energy in order to
answer questions based on information. PSSA
LTS orange pages 76 to 79.