Why the valency of nitrogen and boron is 3?

Fist of all, keep it in mind that both N and B are non-metals and thei compounds are covalent in nature and covalent bond is formed by mutual sharing of electrons. as N requires 3 electrons to make its electronic configuration similar to nearest noble gas so its valency is 3. read more

Boron has electronic configuration 2,3 so it will lose 3 electrons rather than gaining 5 electrons. Thus, the valency of nitrogen and boron is 3. read more

Save for Helium in group 18 (VII,0) which only has two valence electrons, those being its only electrons, the group number determines the valence electron count. The alkali metals all have 1 valence electron, and they are group one. Group 2, the alkali earths, all have 2 valence electrons, and so on. read more