Answers

2015-11-28T16:37:29+05:30
Valency is the  number of free electrons in the valence shell
Valency of nitrogen is three which means that it has 3 electrons free in its last shell for it to react. Same is for boron
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2015-11-28T16:47:22+05:30
Valency is the no of electrons that an atom can gain or lose during a chemical reaction.......
nitrogen has 5 (more than 4)electrons in its outer most shell or orbit
so it is deficit of 3 electrons which it can accept from other element during chemical reaction. when an atom accept electrons it gets negatively charged so the valency of nitrogen is -3 as
but boron has 3 electrons (less than 4 ) so it will readily lose electrons and become positively charge
and the valency will be +3
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