Question

The element containing only one , or seven electrons in the outermost shell show very high chemical reactivity . WHY ?​

Answer 1

Answer:

Valency of an element determines its chemical reactivity.

Therefore, for all elements belonging to a particular group in the periodic table, the number of electrons in the outermost shell, that is the valence electrons will be the same.

Hence, all the elem in that group will show the same chemical reactivity. They will react with different elements in the same way and the molecular formula of their compounds will be similar.

Hence, they have the same chemical properties.

Answer 2

Because of this chemical inactivity, these gases are called as noble gases (earlier these were called inert gases). ... The elements containing only one or seven electrons in their outermost shell show greater chemical reactivity, i.e., such elements react very fast with other elements.