How can I calculate the valency of an element?Pl. suggest some formulas.?

Question

Here is a question.
Taking valency of 02 as 2,Derive the valency of Nitrogen in -
N2O,NO,NO2
Please explain.

Answer 1

These links may help:

http://www.jghs.edin.sch.uk/mathscience/chemistrynotes/topic4.html
http://www.chelationtherapyonline.com/technical/p19.htm

Answer 2

Each oxygen will have a minus 2 charge. The compounds are neutral, so the positive charges on nitrogen will be the absolute value of the charges of the oxygens. In the first one, you have two N's to one O. So each N is +1. Bet you can take it from there.

Answer 3

"The valence of many elements is determined from their ability to combine with hydrogen or to replace it in compounds. For example, one oxygen atom combines with two hydrogen atoms to form water and the valence of oxygen is thus determined to be 2. Similarly, chlorine accepts one electron in combining with a single atom of hydrogen to form hydrogen chloride, HCl, and chlorine’s valence is 1. Zinc does not combine with hydrogen but does replace it in compounds; in a typical replacement reaction, one zinc atom replaces two hydrogen atoms, as in the equation Zn+H2SO4 => ZnSO4+H2, so that zinc has a valence of 2."
http://www.bartleby.com/65/va/valence.html