Question

Assertion: ${\mathrm{PF}}_5,{\mathrm{SF}}_6$ and ${\mathrm{H}}_2{\mathrm{SO}}_4$ are examples of expanded octet molecules.

Reason: Octet rule is not applicable to the second-period elements of the periodic table.

• A. Both Assertion and Reason are false.
• B. Assertion is true, but Reason is false.
• C. Both Assertion and Reason are true. The reason is the correct explanation of Assertion.
• D. Both Assertion and Reason are true. The reason is not the correct explanation of Assertion.

Answer 1

The correct option is B

Assertion is true, but Reason is false.

The explanation for the Assertion statement

• Hypervalent compounds are main group elements that have expanded octets and make more bonds than would be predicted by the octet rule.
• It indicates the presence of more than eight electrons surrounding a single atom.
• The octet rule is violated by the central phosphorus $\left(\mathrm{P}\right)$ atom in the ${\mathrm{PF}}_5$ molecule which is bonded to five Florine $\left(\mathrm{F}\right)$ atoms and has a total of $10$ bonding electrons.
• The central Sulphur $\left(\mathrm{S}\right)$ atom in the molecule ${\mathrm{SF}}_6$ is bonded to six fluorine atoms and has $12$ bonding electrons
• The central Sulphur atom in the ${\mathrm{H}}_2{\mathrm{SO}}_4$ molecule possesses an extended octet and has $12$ bonding electrons.

The explanation for the Reason statement

• The octet rule does not apply to elements in and above the third period of the periodic table
• Hence it applies to the elements present in the second period.

Therefore, the correct option is (B) Assertion is true, but Reason is false.