Question

An atom has a mass number $A$ and atomic number $Z$.

How many electrons are revolving around the nucleus?

Answer 1

Mass number: The total number of protons and neutrons is called the mass number.

• It is represented by A.
• Mass number = the total number of a proton + the total number of neutrons.
• Number of neutron = Mass number – Atomic number
• n = A – Z

Atomic number: The total number of proton or electrons in an atom is called atomic number.

• It is represented by Z.
• Atomic number = total number of electrons or a total number of protons.

Electrons: It is the electronegative particles of the atoms.

• It is present in the orbitals shell of the atoms.
• It is revolving around the nucleus.
• It is also equal to the atomic number of the atoms.
• Number of electrons = an atomic number of atoms.
• So, all the electron which is equal to the atomic number revolves in a shell or orbitals around the nucleus.