Question

The number of $d$ electrons in Fe is equal to which of the following?
(i) Total number of $s$-electrons of Mg
(ii) Total number of $p$-electrons of Cl 
(iii) Total number of $p$-electrons of Ne

• A. i, ii only
• B. ii, iii only
• C. i, iii only
• D. i, ii, iii

Hint:

To compare the number of $d$-electrons, look at the electron configuration and count the electrons in the $d$-subshell. Similarly, for $s$- and $p$-electrons, examine their respective subshells.

Answer 1

The Correct Option is C

The electron configuration of iron (Fe) is: $${Fe}: [{Ar}] 3d^6 4s^2$$ Thus, the number of $d$-electrons in Fe is 6.
Now, let's examine the other options:
- For Magnesium (Mg), the electron configuration is: $${Mg}: [{Ne}] 3s^2$$ Thus, the total number of $s$-electrons in Mg is 2.
- For Chlorine (Cl), the electron configuration is: $${Cl}: [{Ne}] 3s^2 3p^5$$ Thus, the total number of $p$-electrons in Cl is 5.
- For Neon (Ne), the electron configuration is: $${Ne}: [{He}] 2s^2 2p^6$$ Thus, the total number of $p$-electrons in Ne is 6. From the above analysis: 
- The number of $d$-electrons in Fe (6) is equal to the total number of $p$-electrons in Cl (5) and Ne (6).
Therefore, the correct options are ii and iii only.