DEF. 0F VELENCEY      1.NO. OF ELECTRON IN LAST SHELL.e.g H IS 1 ELECTRON IN LAST SHELL SO ITS VELENCEY IS 1                                           2.ABILITY IN AN ATOM TO SHARING OF ELECTRON e.g Ca SHARE 2 ELECTRON,H SHARE 1 ELECTRON .SO Ca HAS 2 VELENCEY & H HAS 1                                           3.ABILITY IN AN ATOM TO GAIN OR GIVE ELECTRON e.g NA GIVE 1 ELECTRON & Cl ACCEPT 1 ELETRON .SO BOTH VELENCEY IS 1.                                                                             4.WHEN AN ATOM GIVE 1,2 OR 3 ELECTRON ITS VELENCEY WILL BE POSITIVE  1,2 OR 3                                                                  5.WHEN AN ATOM ACCEPT 1,2 OR 3 ELECTRON ITS VELENCEY WILL BE NEGATIVE RESPECTIVILY 1,2,OR 3 

roup	Valence 1	Valence 2	Valence 3	Valence 4	Valence 5	Valence 6	Valence 7	Typical valences
1 (I)	NaCl							1
2 (II)		MgCl2						2
13 (III)			BCl3, AlCl3 Al2O3					3
14 (IV)		CO		CH4				4
15 (V)		NO	NH3 PH3 As2O3	NO2	N2O5 PCl5			3 and 5
16 (VI)		H2O H2S		SO2		SO3		2 and 6
17 (VII)	HCl		HClO2	ClO2	HClO3		Cl2O7	1 and 7