Question

how to get know whether the valency of an element is positive or negative

Answer 1

Heya

If an atom gains electron, then it contains negative charge and valency will be negative.

For example :- If Chlorine (Cl) gains one electron, then it's valency will be -1.

If an atom loses electrons, then it contains positive charge and valency will be positive.

For example :- If Sodium (Na) loses one electron, then it's valency will be +1.

Hope this helps.

Answer 2

Answer:

(hint) electrons in a atom can only move and they have a negative charge

Explanation:

simply...if an element loses any electron then negative charge from that particular element get deducted and positive charge is more, therefore, its valency will be  negative

simply...if an element gains any electron then negative charge from that particular element get increased and positive charge is less, therefore, its valency will be positive