Question

how to know the valency of an element by atomic number​

Answer 1

Answer:

 The Valency of the atom of an element is determined by the number of electrons in its outermost shell, i.e. valence shell. For atoms with less than 4 or less electrons in the valence shells (i.e. valence electrons), valency = no. of electrons. For atoms with more than 4 valence electrons, valency = 8 - (no.

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Answer 2

Answer:

the valency is dependent on the no. of electrons in the valance shell ie- the last shell. the first shell need a duet and all the other shells need an octet to complete the atom.

first arrange the atomic no in the shells. for eg, we have oxygen whose atomic no. is 8.

therefore the electronic configuration will be ( 2,6)

next step subtract the last shell's electrons from 8 ( because they form in an octet)

∴8-6= 2.

thus the valency is 2 whereas the valance electrons are 6

Explanation: