Question

· Explain why are the following statements not correct:
(0) All groups contain metals and non metals.
(ii) Atoms of elements in the same group have the
same number of electron(s).
(iii) Non-metallic character decreases across a period
with increase in atomic number.
(iv) Reactivity increases with atomic number in a group
as well as in a period.


Only for science students ​

Answer 1

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) No two elements have the same number of electrons instead atoms of the same elements in the same group have the same number of valence electrons.

iii) Non-metals have the tendency to gain electrons to attain stable configuration and therefore are said to be electronegative. As we move from left to right the increase in atomic number and decrease in size results in a greater nuclear pull. As a result the non-metallic character increases across a period.

iv)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.