Variation of Valency
(a). Variation along period: – Valency of normal elements i.e. s and p-block elements first increases from 1 to 4 and then decreases from 3 to zero. But d-block elements show variable valencies. f-block elements exhibit only electropositive valency, the most common being 3.
(b). Variation down the group :– On moving down a group, the number of valence electrons remains same and therefore, all the elements in a group exhibit same valency. For example, all the elements of group 1 have valency equal to one and those of group 2 have valency equal to two.
CTM:– Valency can be determined as follows:-
If no. of electrons in valence shell is 1 to 4 then valency of atom is equal to no. of electrons in valence shell. If no. of electrons in valence shell is 5 to 8, then valency is equal to valence electron -8
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