Question

The element that does NOT exhibit allotropy is?
A ) Phosphorus
B ) Arsenic
C ) Antimony
D ) Bismuth

Answer 1

Hint: The element that exhibits variable oxidation states, is the element that exhibits allotropy. If the element does not exhibit variable oxidation states, then the element does not exhibit allotropy. Allotropy is the property of few substances to exist in two or different forms in the same physical state.

Complete answer:
> Allotropy is the property of few substances to exist in two or different forms in the same physical state. Different structural modifications of the element, in which the bonding arrangement of atoms is different, are the allotropes.
> In group 15 all elements except, nitrogen and bismuth, show allotropy.
> Several allotropic forms of phosphorus are present. Major allotropes of phosphorus include white, red and black phosphorus. Arsenic has six different allotropes out of which three are in amorphous form. Brittle, steel grey solid is the most stable and common allotrope of arsenic. Antimony has four allotropes. One of these is explosive.
> When vapour of Arsenic or antimony is condensed rapidly, an unstable form is formed. The structure of this unstable form is similar to that of white phosphorus. This unstable form is then converted to denser, metallic allotrope, which has a structure similar to that of black phosphorus.
The element that does NOT exhibit allotropy is bismuth.

Hence, the option D ) bismuth is the correct answer.

Note: Bismuth shows inert pair effect. Hence, it does not exhibit variable oxidation states. It adopts layer structure. Hence, bismuth does not show allotropy. Bismuth is unusual as it expands during solid formation.