Ions are atoms that have gained or lost electrons to become charged. Cations have a positive charge from losing electrons while anions have a negative charge from gaining electrons. Atoms form stable ions by gaining or losing electrons to achieve a full outer electron shell. Isotopes are versions of an element with different numbers of neutrons. Some isotopes are stable while others are unstable. Isotopes can be written with the element name and mass number, such as Carbon-14. The average atomic mass shown on the periodic table is calculated from the relative abundances of naturally occurring isotopes.

1. Ions & Isotopes

2. Ions are charged atoms that have
either gained or lost electrons.
Cations = positive charge
Anion = negative charge

4. Atoms prefer to have full outer orbitals, which is their most
stable state. Atoms that have a nearly full or nearly empty
valence shell are unstable and easily react to give/get e-’s.
Some *** Non-metals gain electrons and metals lose
electrons.

5. Non-metals gain electrons while metals lose electrons.
Normal Stable
Be Cl
Be Cl

6. Create the stable ion form for the following atoms:
(must have full outer shell)
Na Mg
Br O

7. Isotopes are versions of an element with different #’s of
neutrons. Some are stable while others are not.
Remember, that changing at atom’s protons changes what
element it is.

8. Isotopes can be expressed in a
couple of ways. For example,
Carbon usually has 6
neutrons, but an isotope of C
can have 8. This isotope can
be written as:
• Carbon-14
• .
How many e-, p+ and No
does C-14 have?
14
C6

9. Carbon Isotopes

10. Carbon Isotopes
Fill in the following:
C-13
P+:
e-:
No:
C-12
P+:
e-:
No:
C-14
P+:
e-:
No:

11. Average Atomic Mass
Different isotopes exist in different quantities. The atomic
mass shown on the periodic table represents the AVERAGE
mass of these isotopes.
How could the average mass be calculated?

12. Practice Q
1. If 2 atoms are isotopes that weigh 10amu and 15amu
which are found in equal quantities, what is the average
atomic mass?
2. Two isotopes of X-23 and X-30 have been found in
nature. If the relative abundances of each are 75% and
25% respectively,
Calculate the average atomic mass of X.