Question

what is valancy define
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Answer 1

The elecrons present in outer most sheep of an atom

Ex: sodium has 1electron in its outer most shell

So it has valency 1

Answer 2

valency is a combining power with other atoms when it forms a molecule or a chemical compound

Extra info:-

Now let us know about the valency of 10 elements valency

1.hydrogen = 1

2.helium = 0

3.Lithium = 1

4.Berrylium = 2

5.Boron = 3

6.carbon = 4

7.Nitrogen = 3

8.oxygen = 2

9.flourine = 1

10.Neon = 0