In general chemistry, isotopes are substances that belong to one specific element. So, they all have the same atomic numbers. But they only differ in the mass numbers, or the number of protons and neutrons in the nucleus. In a nutshell, they only differ in the number of neutrons.
For Nickel, there are 5 naturally occurring isotopes. Their identities, masses and relative abundance are listed below
Isotope Abundance Atomic Mass
Ni-58 68.0769% 57.9353 amu
Ni-60 26.2231% 59.9308 amu
Ni-61 1.1399 % 60.9311 amu
Ni-62 3.6345% 61.9283 amu
Ni-64 0.9256% 63.9280 amu
To determine the average atomic mass of Nickel, the equation would be:
Average atomic mass = ∑Abundance×Atomic Mass
Using the equation, the answer would be:
Average atomic mass = 57.9353(68.0769%) + 59.9308(26.2231%) + 60.9311(1.1399%) + 61.9283(3.6345%) + 63.9280(0.9256%)
Average atomic mass = 58.6933 amu