Question

How can the mass number be calculated?

Answer 1

To solve this we must know that the sum of the number of protons and the number of neutrons in the nucleus of an atom of an element is known as the mass number of the element. The mass number is also known as the atomic mass number or the nucleon number.

Complete step by step answer:
- We know that the general representation of elements is $_{\text{Z}}{{\text{X}}^{\text{A}}}$. - Where ${\text{Z}}$ is the atomic number of the element, ${\text{A}}$ is the mass number of the element and ${\text{X}}$ is the atomic symbol of the element.
- The number of protons in the nucleus of the atom or the number of electrons surrounding the nucleus of the atom of any element is known as the atomic number of the element.
- The sum of the number of protons and the number of neutrons in the nucleus of an atom of an element is known as the mass number of the element.

Thus, the equation to calculate the mass number is as follows:
${\text{Mass number}} = {\text{Number of protons}} + {\text{Number of neutrons}}$
- If the number of protons and the number of neutrons of an element are given you can calculate the mass number.
- Thus, the mass number of an element can be calculated by adding the number of protons and the number of neutrons.

Note: Consider the following examples: A carbon atom has 6 protons and 6 neutrons. Thus, the mass number of the carbon atom is 12. The carbon atom is represented as $_{{\text{12}}}{{\text{C}}^{\text{6}}}$. A carbon atom has 6 protons and 7 neutrons. Thus, the mass number of the carbon atom is 13. The carbon atom is represented as $_{{\text{13}}}{{\text{C}}^{\text{6}}}$. $_{{\text{12}}}{{\text{C}}^{\text{6}}}$ and $_{{\text{13}}}{{\text{C}}^{\text{6}}}$ are known as isotopes of each other.