Question

How will you find the valency of chlorine, sulphur and magnesium (atomic no. of Cl-17, S-16,
Mg-12)?
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Answer 1

Explanation:

Cl-2, 8, 7

therefore valency 1 to complete octet(-1)

S- 2,8,6

therefore valency 2 to complete octet(-2)

Mg-2,8,2

similarly valency 2(+2)

Answer 2

the valency of an element is it's combining capacity and it can found by looking at the number of electrons in the outermost shell

Cl-2,8,7

chlorine has 7 electrons in its outmost shell so it will gain one electron to form an anion. it is easier to gain 1 electron than to lose 7. hence it is monovalent

S-2,8,6

sulphur has 6 electrons in the valence shell. It will gain 2 electrons to reach octet configuration.

it forms a bivalent anion

Mg-2,8,2

magnesium will lose 2 electrons . it forms a bivalent cation

hope this helps ,