Q2 / 150 · MHT CET 2026 (16 April Shift 2) · Chemistry
What is the number of unpaired electrons present in ground state of Silicon and Chromium, respectively ?
- A2 and 4
- Correct answerB2 and 6
- C0 and 6
- D4 and 5
Solution
The atomic number of Silicon (Si) is $14$.
The electronic configuration of Si is $1s^{2} 2s^{2} 2p^{6} 3s^{2} 3p^{2}$.
In the $3p$ subshell, there are $2$ electrons which occupy separate orbitals according to Hund's rule. Thus, Si has $2$ unpaired electrons.
The atomic number of Chromium (Cr) is $24$.
The electronic configuration of Cr is $[Ar] 3d^{5} 4s^{1}$.
In the $3d$ subshell, there are $5$ unpaired electrons and in the $4s$ subshell, there is $1$ unpaired electron. Thus, Cr has $6$ unpaired electrons.
The number of unpaired electrons in Si and Cr are $2$ and $6$, respectively.
Answer: 2 and 6
The electronic configuration of Si is $1s^{2} 2s^{2} 2p^{6} 3s^{2} 3p^{2}$.
In the $3p$ subshell, there are $2$ electrons which occupy separate orbitals according to Hund's rule. Thus, Si has $2$ unpaired electrons.
The atomic number of Chromium (Cr) is $24$.
The electronic configuration of Cr is $[Ar] 3d^{5} 4s^{1}$.
In the $3d$ subshell, there are $5$ unpaired electrons and in the $4s$ subshell, there is $1$ unpaired electron. Thus, Cr has $6$ unpaired electrons.
The number of unpaired electrons in Si and Cr are $2$ and $6$, respectively.
Answer: 2 and 6
Hence, the correct answer is option: 'B'.