Question

Which member of the 15 group elements does not show allotropy?

• A. Nitrogen
• B. Phosphorus
• C. Arsenic
• D. Antimony

Answer 1

The Correct Option is A

The 15 group elements, also known as the nitrogen group or pnictogens, include nitrogen, phosphorus, arsenic, antimony, and bismuth. Allotropy refers to the existence of an element in more than one form, with different physical and chemical properties. Among the 15 group elements:

• Nitrogen: Exists primarily as a diatomic molecule (N₂) and does not exhibit other allotropic forms under normal conditions.
• Phosphorus: Shows allotropy with forms such as white, red, and black phosphorus.
• Arsenic: Exhibits allotropy with gray, yellow, and black forms.
• Antimony: Shows allotropy with metallic and nonmetallic forms.

Therefore, the member of the 15 group elements that does not show allotropy is nitrogen.

Answer 2

Nitrogen does not exhibit allotropy, which means it does not exist in multiple structural forms in the same physical state, unlike other elements such as phosphorus, arsenic, and antimony, which exhibit allotropy. Allotropes are different forms of the same element that differ in the arrangement of atoms in their structure.

Nitrogen primarily exists as a diatomic molecule (N₂) under standard conditions, where two nitrogen atoms are bonded together with a strong triple bond. This simple molecular form is stable and inert. In contrast, elements like phosphorus can exist in several allotropes, including white, red, and black phosphorus, each with different atomic arrangements and properties. Similarly, arsenic and antimony also exhibit different allotropes, which have varying physical and chemical characteristics.

The lack of allotropy in nitrogen is due to its strong triple bond in the N₂ molecule, making it stable and not readily forming other structural modifications. The absence of multiple allotropes for nitrogen contrasts with the greater variety found in some other elements in the periodic table.