1. Parts of
the Atom

2. Relative electric charge
Subatomic Particles
particle
symbols
Relative electric charge
Mass number
Relative mass (amu)
Actual mass (kg)
electron
proton
neutron -1 e-
0.0055
9.1 x 10-31 p+
1.007 +1 1
1.7 x 10-27 n0 1
1.008
1.7 x 10-27
Mass number of an atom with:
The electron doesn’t contribute any significant mass to the atom.
1 proton
= 1 (1.007amu)
1 electron
= 0 ( amu)
1 neutron
= 1 (1.008 amu)
2 amu

3. Atomic number is the number of protons
Mass number is the number of protons + neutrons.
An atom with 6 protons and 7 neutrons has an atomic number of 6 and a mass number of 13.
This atom would be carbon because carbon’s atomic number is 6.

4. Isotopes Isotopes are atoms of the same element with different masses.
Not all atoms of an element are the same.
Not all atoms of hydrogen are the same.
There exists 3 isotopes (types) of hydrogen.
Substitute the word variety (or flavors).

5. H C Isotopes of Hydrogen Isotope Nuclear Symbol Number of protons
Number of electrons
Number of neutrons
hydrogen-1
hydrogen-2
hydrogen-3 1 H 1 1 2 1 H 1 1 1 3 1 H 1 1 2
mass number=
protons + neutrons
protons + neutrons
1 p + 2 n H 3 1
6 p + 7n C 13 6
atomic number=
protons
1 p
protons
6 p

6. Isotopes of Hydrogen Isotope Nuclear Symbol Number of protons
Number of neutrons
Mass number
hydrogen-1
hydrogen-2
hydrogen-3 1 H 1 1 2 1 H 1 1 2 3 1 H 1 2 3
Mass number is the number of protons + neutrons.

7. Ions Cl + e- a Cl-1 S + 2e- a S-2 Na a Na+1 + e- Ions
(not to be confused with isotope)
Ion is an atom that has either lost or gained electrons and therefore has a charge. (not neutral)
Cl + e- a Cl-1
Ions
S + 2e- a S-2
Na a Na+1 + e-

8. Symbol
Atomic number
Mass number
# of protons
# of neutrons
# of electrons
charge O 9 K 39 19 40
F-1 -1 8 17 8 8 19 19 20 19 19 21 19 9 9 10 10
Use the periodic table to find atomic number.
Atomic number = # of protons.
Mass number = # of protons + neutrons
Since the charge is zero, # of protons = # of electrons