NUCLEUS

Define a nucleus.

Generally the nucleus of an atom has the following features:

NUCLEUS

The center part of an atom is called Nucleus.

SHAPE OF NUCLEUS

Nucleus has spherical shape.

SIZE OF NUCLEUS

Nucleus has very small size. Diameter of nucleus is about 1x10 -14m.

CHARGE OF NUCLEUS

It has positive charge due to presence of proton.

NUCLEON

Neutron and protons are collectively known as Nucleon.

ATOMIC NUMBER OR CHARGE NUMBER

Total number of proton in the nucleus of an atom is called its atomic number.
OR
Total number of electrons in an atom is also known as atomic number, because
in an atom number of an electron is always equal to proton.

SYMBOL

It is denoted by z

z = number of protons OR z = number of electron

MASS NUMBER

Total number of a proton and neutrons in an atom is called Mass number.

SYMBOL

It is denoted by (A).

FORMULA

A = no. of proton + no of neutron
A = p+ n 
OR 
A = Z + n.