Explain: Determining the Subatomic Particles of Atoms
8.5 B - identify that protons determine an element's identity and valence electrons determine its chemical properties, including reactivity.
Each element of the periodic
table is made of only one kind
of atom. Atoms are
Parts of
an atom
composed of subatomic
Neutral
atoms
In a neutral atom, the positive charges of the protons are balanced by the
particles called protons,
neutrons, and electrons.
negative charges of the electrons. Neutrons are neutral and do not affect the
charge of an atom.
Periodic
table info
Use the periodic table to determine the number of protons, electrons, and
neutrons.
1. Identify the number of protons. The
Atomic
number
atomic number represents the number
of protons.
Ex.) The atomic number for Oxygen is 8.
That means all atoms of oxygen have 8
protons.
Atomic Number = Number of Protons
2. Identify the number of electrons. In a
neutral atom, the number of positive
charges must be balanced by an equal
Number of
electrons
number of negative charges.
Ex.) Fluorine has an atomic number of 9.
That means there are nine positively
charged protons. Since it is a neutral
atom, it also has 8 negatively charged
electrons.
Atomic Number = Number of Protons = Number of Electrons
A
P
E (all three are equal in a neutral atom!)
3. Identify the number of neutrons. Round the atomic mass to the
nearest whole number. The atomic mass represents the number of
protons plus the number of neutrons in the nucleus.
A.) Fluorine has an atomic mass of 18.998. Round it to the nearest
Atomic
mass
whole number which is 19.
B.) To find the number of neutrons:
Atomic Mass
Number
Ape
man
=
Number
Number of
Neutrons
19
-
9
=
10
M
-
A
=
N
Atomic
Remember
Atomic
-
Number
A
Atomic Mass
Number
M
=
Number of
Protons
=
P
=
Atomic
-
=
Number
-
=
A
=
Number of
Electrons
E
Number of
Neutrons
N
Another way to determine the number of
protons, neutrons, and electrons…
Fluorine -- F
practice
Atomic Number
9
Atomic Mass Number
19
Number of Protons
9
- Atomic Number
9
Number of Electrons
9
Number of Neutrons
10
Another way to determine the number of
protons, neutrons, and electrons…
More
practice
Aluminum -- ___
Atomic Number
___
Atomic Mass Number
___
Number of Protons
___
- Atomic Number
___
Number of Electrons
___
Number of Neutrons
___
Now, it’s your turn.
Sodium -- ___
Atomic Number
___
Atomic Mass Number
___
Number of Protons
___
- Atomic Number
___
Number of Electrons
___
Number of Neutrons
___
Atomic Number
___
Atomic Mass Number
___
Number of Protons
___
- Atomic Number
___
Number of Electrons
___
Number of Neutrons
___
______________
___
______________
___
______________
___
______________
___
______________
___
______________
___
______________
___
______________
___
______________
___
______________
___
______________
___
______________
___
Nickel -- ___
Manganese -- ___
Argon -- ___