Question

Explain why the following statements are not correct? (Answer any three

from the following)

i)All groups contain both metals and non-metals

ii)In group I, reactivity decreases with increases in atomic numberiii)Elements in a period become more metallic with increasing atomic

number

iv)Atoms of elements in the same group have the same number of electrons​

Answer 1

Answer:

1st is not

correct statement

Answer 2

Answer:

i) Since the elements in a group have same number of valence electrons, they can either contain metals or non-metals like alkali and alkaline metals have only metals whereas halogens are non-metals.

ii)On moving from left to right in a period, the reactivity first decreases and then increases since the tendency to lose electrons first decreases on going from left to right and then from P to Cl, tendency to gain electrons increases, so reactivity increases then. In case of a group, reactivity increases on going down since the tendency to lose electrons increases but for non-metals, reactivity decreases on going down the group as the tendency to gain electrons decreases down the group.

iii)The non-metallic character increases across a period with increase in atomic number. This is because across the period, the size of atom decreases and the valence shell electrons are held more tightly.

iv) On moving from left to right in a period, the reactivity of elements first decreases and then increases, while in groups, chemical reactivity of metals increases going down the group whereas reactivity of non-metals is decreases down the group.