# ATOMIC NUMBER AND MASS NUMBER

## ATOMIC NUMBER :

The number of Protons present in the nucleus of an atom is known as its ATOMIC NUMBER.

- It is generally denoted by the letter 'Z'
- This was proposed by Moseley based on X-ray spectral studies.
v1/2 = a(Z-b)

where,

v = frequency of X-ray of element

z = atomic number of the element a and b are constants

atomic number of an element can be written as:

- Number of protons present in the nucleus of the atom
- Number of electrons present in the neutral atom of the element
- Positive charge of the nucleus of the atom
- Serial number of the element in the periodic table

Atomic number(Z) = number of protons = number of electrons

## MASS NUMBER :

The sum of the number of Protons and neutrons present in the nucleus of an atom is known as its MASS NUMBER.

- It is generally denoted by the letter 'A'
- Mass number of an element is a whole number never a fractional value.
- Atomic mass of an element corrected to the nearest whole number will be the mass number of the element

Mass number(A) = Atomic number(Z) + Number of neutrons

### Now lets calculate 'A' and 'Z' of element

Enter the name of any element from Hydrogen to calcium ENTER ELEMENT NAME:
Atomic number :
Mass number :

#### note:

##### elements between hydrogen and calcium:

hydrogen,helium,lithum,beryllium,boron,carbon,nitrogen,oxygen,fluorine,

neon,sodium,magnesium,aluminium,silicon,phosphorus,sulphur,chlorine,

argon,potassium,calcium.