Question

Assertion: The elements with electronic configuration ${\left[\mathrm{Xe}\right]}^{54}4f^{1}5d^{1}6s^2$ is a $d$ block element.

Reason: The last electron enters the $d$-orbital.

• 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 A

Both Assertion and Reason are false.

The explanation for the Assertion statement

• The electronic configuration is as follows:

${\left[\mathrm{Xe}\right]}^{54}4f^{1}5d^{1}6s^2$

• It is the electronic configuration of the lanthanoid series.
• The elements are the $f$-block element.

The explanation for the Reason statement

• Lanthanoid elements have incompletely filled $4f$ subshells.
• The last electron enters the $4f$ orbital.

Therefore, the correct option is (A) Both Assertion and Reason are false.