Question

(v) Identify the reason for the gradual change in non-metallic character of the elements in the third period.
a) Non-metallic character decreases as the effective nuclear charge acting on the valence shell electrons
increases across a period.
b) Non-metallic character increases as the valence electrons increases across the period.
c) Non-metallic character decreases due to the repulsion between the electrons in the valence shell.
d) Non-metallic character increases as the effective nuclear charge acting on the valence shell electrons
increases across a period.​

Answer 1

Answer:[a] Across a period effective nuclear charge acting on the valence shell electrons increases which decreases the tendency to lose electrons. Hence metallic character decreases and non-metallic character increases across a period.

[b] The tendency to gain electrons increases on moving across a period due to an increase in the nuclear charge and decrease in the atomic size. Hence, the non-metallic character increases across a period. As we move down the group, the non-metallic character decreases due to increase in the atomic size.

[c] As one moves from left to right in a period, there is consecutive addition of one proton in the nucleus and one electron in the valence shell of the element. However, the electron is always added in the same valence shell period.

 

Atoms of metals always lose electrons & are called electropositive. Non metals either gain or share electrons and hence are called Electronegative. Hence on moving from left to right in a period electropositiv character or metallic character of elements gradually decreases and electronegative character or non metallic character increases .

[d]Across a period effective nuclear charge acting on the valence shell electrons increases which decreases the tendency to lose electrons. Hence metallic character decreases and non-metallic character increases across a period.