Question

what is important of valancy?please answer me now in detail...

Answer 1

valency is the combining capacity of an element .It measures the combining power of chemical compound made by that element. valency also determines that an element is a metal or a non-metal because metal has the tendency to donate electrons and non metals to gain electrons. Thus, valency plays an important role in various conditions

Answer 2

we know , any atom form form by no of electrons , protons , neutrons , positrons extra -extra .
protons and neutrons are found in the nucleus. but in case of electrons, this doesn't exist in the nucleus . electrons move around the nucleus . due to this reason electrons have tendency to eject from atom or any orbit of atom .
it means due to instability of electrons atom , convert in ion.
now , if you have answer , why do any atom combine with another ?
the answer is instability . atom get stable when it combine with another atom . how stability come ? answer is when atom loss or except no of electrons and complete octet after lossing electrons then it will be stable .

it means any compound forming when atom loss , gain , or share of electron to another arom.

now ,
according to Octet rule :-
the outermost shell of an atom is called the valence shell . and the electrons present in it are called valence electrons .
# elements that are not have complete Octet have a high tendency to attain Octet configuration either by lossing or gaining or sharing electron to with of same or other elements .

# An atom which electrons are easily loss ? e.g valence electrons .

in which shell electrons gain to the atom ? e.g velence shell .

now , we can say valence shell or valence electrons are most important for forming compound . e.g valency are most important for forming compounds.
because valency is co-related to valence shell or valence electrons.
example :- Carbon have four valence electrons , so its valency 4

Oxygen have 6 valence electrons
so, it valency = 8 -6 =2