Question

Define the following terms : (a) Atomic number (b) Mass number

Answer 1

(a) Atomic number:

1. The atomic number of an element is equal to the number of protons in the nucleus of an atom.
2. The atomic number is denoted by $\mathrm{Z}$.

Example:

1. Consider a Carbon $\mathbf{\left(}\mathbf{C}\mathbf{\right)}$ atom.
2. Carbon has $6$ protons.
3. Thus, atomic number of Carbon is $6$.

(b) Mass number:

1. The mass number is defined as the sun of number of protons and number of neutrons in an atom.
2. The mass number is denoted by $\mathrm{A}$.

Example:

1. Consider a Carbon $\mathbf{\left(}\mathbf{C}\mathbf{\right)}$ atom.
2. Carbon has $6$ protons and $6$ neutrons
3. Thus, mass number of Carbon is $12$.