Answers

2015-05-01T23:19:50+05:30

just remember the atomic number or periodic table and arrange  electrons in shells . valency  is the electrons present in outermost shell like

1)carbon ; C

atomic number: 6

electronic C ; 2,4

4 is the valency

2) calcium ; Ca

atomic number : 20

electronic C: 2, 8,8,2

2 is the valency

4 2 4
2015-05-02T10:41:59+05:30
Valency is the number of electrons present in the outermost shell.
for example:
electronic configuration of of chlorine =1s2 2s2 2p6 3s2 3p5
valency=2+5=7. As the last two digits are the same(3)

electronic configuration of sodium=1s2 2s2 2p6 3s1
valency = 1
3 2 3