Question

Define atomic number and mass number. how can you represent an atom by using atomic number and mass number . Give two examples.

Answer 1

Atomic number:

• The total number of protons in the nucleus of an atom gives the atomic number of that atom.
• It is represented by the symbol Z.

Mass number:

• The number of protons and neutrons combined gives the mass number of an atom.
• It is represented by the symbol A.

The representation of atoms by using atomic numbers and mass numbers is given below:

${}_{\mathrm{Z}}{}^{\mathrm{A}}\mathrm{X}$ where X is the element, Z is the mass number, and A is the atomic number.

For Example:

• ${}_6{}^{12}\mathrm{c}$-In this atom, the atomic number is 6 and the mass number is 12.
• ${}_2{}^4\mathrm{H}e$-In this atom, the atomic number is 2 and the mass number is 4.