Subatomic Particles
Using the Periodic Table
Atomic
Number
Mass
Number
N
14.0067
7
Symbol
Atomic Number The number of protons
in the nucleus
 Every element on
the Periodic Table has
an unique atomic
number
Determine the number of
PROTONS in each:
1.
2.
3.
4.
5.
Na
O
Br
Zn
H
1. 11
protons
2. 8 protons
3. 35 protons
4. 30 protons
5. 1 proton
Mass Number The number of protons and
neutrons (you need to round the
decimal number first)

To find the number of neutrons:
Mass Number - # of protons
From the atomic number
Determine the # of protons and
neutrons for each of the following:
1. H
2. Cl
1.
2.
3. Mg
3.
4. Ca
4.
5. I
5.
1 proton and 0 neutron
17 protons and 18
neutrons
12 protons and 12
neutrons
20 protons and 20
neutrons
53 protons and 74
neutrons
Charge of an atom
 Atoms
overall charge is
always zero (they are
neutral)
 To achieve this, the
positively charged protons
must be equal to the
negatively charged electrons
P+E=0
for all atoms
Determine the number of protons,
neutrons, and electrons in each:
1. K
2. Mn
3. P
4. Al
5. H
1. 19p,
19e, 20n
2. 25p, 25e, 30n
3. 15p, 15e, 16n
4. 13p, 13e, 14n
5. 1p, 1e, 0n
Ions
What atoms turn into when
they gain or lose electrons
 To
find the charge on an ion,
compare the # of protons to
the # of electrons
Example of an Ion
Find the number of protons and
electrons in a neutral Mg atom:
 12 protons and 12 electrons
If Mg loses 2 electrons, what
will happen to its charge?

(+12) + (-10) = +2
Final answer:
Mg+2
The Complete Chemical Symbol
Mass Number
(rounded)
16
8
Atomic Number
-2
Charge