Question

The number of protons present in the nucleus of an atom is known as its mass number.

• A. True
• B. False

Answer 1

The correct option is B False

• Atom consists of mainly 3 subatomic particles which are electrons, protons, and neutrons.
• There is a small, dense, positive center at each atom which is known as the nucleus.
• Positively charged protons and neutral neutrons are present inside the nucleus while negatively charged electrons revolve around the nucleus in a definite circular path known as shells or orbit.
• The atomic number of a neutral atom equals the number of protons in the nucleus.
• The atomic number has the symbol Z.
• The Mass number of an atom refers to the total number of protons and neutrons present in the nucleus.
• The mass number has the symbol A.

Example

Consider the neutral $\mathrm{Sodium}\left(\mathrm{Na}\right)$atom,

• Atomic number(Z) of $\mathrm{Sodium}\left(\mathrm{Na}\right)$ = 11
• Number of protons present in the nucleus = Atomic number(Z) = 11
• Number of protons = Number of electrons = 11

Therefore, the given statement is false i.e., The number of protons present in the nucleus of an atom is known as its mass number.