Question

Define Valency and Atomic Size

Answer 1

1) ​Valency: Valency may also be define as number of valence electron present in outer most shell.

• For element, if the number of electron is ≤ 4 then the valency will be the number of electron present in outer shell.
• If number of electron is > 4 then valency will be (8-n), where n is the number of electron present in outer most shell.

Valency of chlorine: Atomic no. =17

Configuration :2,8, '7 '= (8-7=1) valency is 1

Valency of Magnesium: Atomic number = 12

Configuration : 2, 8, 2 , so valency = 2

2) Atomic size is the distance between the centre of an atom to the outermost shell , in other words it is the radius of the atom.