Answers

2015-04-10T15:58:24+05:30
The number of electrons present in the outer most orbit of an atom is called Valency
valency of oxygen=2
               calcium=2
                nitrogen=3
0
plz mark it as best
tnk u
hey click on thanx
ok
which class u r ?
The Brainliest Answer!
2015-04-10T16:13:46+05:30
The number of unpaired electrons in an atom's outermost shell is known as valency.
hydrogen have 1 valency because it have only one electron in its outer most shell.

Oxygen have 2 valency the atomic number of  oxygen is 8 from spdf for oxygen
1s^2 2s^2 2p^4 when you arrange p orbital 2 electron are remain unpaired. So it have 2 valency  
like this valancy of carbon is 4. 
valancy of nitrogen is 3

1 5 1