Question

1. what is the difference between \mass number\ and \average atomic mass\? give an example.

Explanation:

• Mass Number: It is the sum of the number of protons and neutrons in the nucleus of an atom of a specific isotope. It is a whole number because it counts particles. For example, a carbon - 12 atom has 6 protons and 6 neutrons, so its mass number is \(6 + 6=12\).
• Average Atomic Mass: It is the weighted average of the masses of all the naturally occurring isotopes of an element, taking into account the relative abundance of each isotope. It is usually a decimal number. For example, the average atomic mass of carbon is approximately 12.011 amu. This is because carbon has isotopes like carbon - 12 (abundance ~ 98.93%), carbon - 13 (abundance ~ 1.07%), and a trace amount of carbon - 14. The calculation is \((0.9893\times12)+(0.0107\times13)\approx12.011\) amu.

Answer:

• Mass Number: Sum of protons and neutrons in a specific isotope's nucleus (whole number, e.g., C - 12 has mass number 12).
• Average Atomic Mass: Weighted average of isotopes' masses (decimal, e.g., C has average atomic mass ~ 12.011 amu).