ATOMIC NUMBER (Z)

ATOMIC NUMBER (Z)

The number of protons is the nucleus of an atom of a given element is called the atomic number of that element.

or

Atomic number is the number of protons present in the atom of an element. It is denoted. by “Z”

Atomic number = Number of protons = Number of electrons (in a neutral atom)

Atomic number = Number of protons (in an ion)

e.g. 11Na

• Atomic number of sodium is 11
• Nucleus of sodium has 11 protons.
• Nucleus of sodium has 11 units of positive charge.
• There are 11 electrons, revolving round the nucleus of sodium.