Question

helium atoms has 2 electrons in its balanced she'll but it balance is not 2 .explain

Answer 1

1. Valency is the combining capacity of an element.

2. Helium has two Valence electrons.

3. The K shell of an atom has the capacity of holding 2 electrons.

4. As the penultimate shell of helium atom is completely filled. It is balanced and stable and chemically inert

Answer 2

Valency is the combining capacity of an element. For a non-metal valency= 8 - Valency electron.(no. of electrons in the outermost shell of the atom. For example: Valency of Oxygen is 2 that is 8-6(valence electons) If Oxygen gets two more electons then is gains stability ie. forms its octet. Some transition metals have variable valency. ex:Fe. But generally valency of metal=valence electrons ex: sodiun(Na) has a valency of 1 ie. If it loses it one electron it gains stability.