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:

  1. 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) $=4$



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