pBlock ElementsII - Result Question 2
####2. The number of pentagons in $C _{60}$ and trigons (triangles) in white phosphorus, respectively, are (2019 Main, 10 April II)
(a) 20 and 3
(b) 12 and 4
(c) 20 and 4
(d) 12 and 3
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Answer:
Correct Answer: 2. (b)
Solution:
- In $C _{60}$ (Buckminster fullerene) twenty hexagons and twelve pentagons are present which are interlocked resulting a shape of soccer ball. Every ring in this structure is aromatic.
Phosphorus has large atomic size and less electronegativity, so it forms single bond instead of $p \pi-p \pi$ multiple bond. So, it consists of discrete tetrahedral $P _4$ molecule as shown below :
$\therefore \quad$ Number of trigons (triangles) $=4$
