Transcript How to calculate the number of protons, electrons, and

How to Read the Boxes in the Periodic
Table
Step 1: Locate the atomic number.
Atomic number=#Protons
Step 2: Locate the atomic mass and round it up
or down (ex: if the atomic mass is 13.6, then
round it up to 14).
Atomic mass=#Protons + #Neutrons
How to Read the Boxes in the Periodic
Table
Step 3: Calculate the number of neutrons by
subtracting the atomic number from the
atomic mass.
#Neutrons=Atomic Mass-Atomic Number
Step 4: Calculate the number of electrons. This
is simple because the number of protons
always equals the number of electrons in a
neutral atom.
#Electrons=#Protons
How to Read the Boxes in the Periodic
Table
Mnemonic device:
A=P=E
M-A=N
A=atomic number
M=atomic mass
P=protons
E=electrons
N=neutrons
Let’s practice…
How many protons, electrons, and neutrons are
in the following atoms:
1. H
2. Be
3. C
4. S
5. Ne
Hydrogen
Protons = atomic number=1
Electrons=atomic number=1
Neutrons=mass-atomic number=1-1=0
Carbon
Protons=atomic number=6
Electrons=atomic number=6
Neutrons=mass-atomic number=12-6=6
Beryllium
Protons=atomic number=4
Electrons=atomic number=4
Neutrons=mass-atomic number=9-4=5