Out of the following the correct statement(s) is/are ,
(a) Number of subshells present in M-shell is equal to 3
(b) maximum number of electrons present in L shell is equal to 8
(c) number of electron present in subshell is 3(2l + 1),
(d) `Cu^+` is paramagnetic

Options

A. (a),(b) &(c)
B. (b) & (d)
C. (a)&(b)
D. (a), (b), (c) & (d)

Answer

To determine which statements are correct, let's analyze each one step by step.

### Step 1: Analyze Statement (a)
**Statement (a): Number of subshells present in M-shell is equal to 3.**

- The M-shell corresponds to the principal quantum number \( n = 3 \).
- The number of subshells in a shell is equal to \( n \).
- Therefore, for the M-shell (\( n = 3 \)), there are 3 subshells: \( 3s, 3p, \) and \( 3d \).

**Conclusion:** Statement (a) is correct.

### Step 2: Analyze Statement (b)
**Statement (b): Maximum number of electrons present in L shell is equal to 8.**

- The L-shell corresponds to the principal quantum number \( n = 2 \).
- The number of subshells in the L-shell is \( n = 2 \), which means it has \( 2s \) and \( 2p \) subshells.
- The \( 2s \) subshell can hold a maximum of 2 electrons, and the \( 2p \) subshell can hold a maximum of 6 electrons (3 orbitals, each holding 2 electrons).
- Thus, the total maximum number of electrons in the L-shell is \( 2 + 6 = 8 \).

**Conclusion:** Statement (b) is correct.

### Step 3: Analyze Statement (c)
**Statement (c): Number of electrons present in subshell is \( 3(2l + 1) \).**

- The formula for the maximum number of electrons in a subshell is \( 2(2l + 1) \).
- The given formula \( 3(2l + 1) \) is incorrect.

**Conclusion:** Statement (c) is incorrect.

### Step 4: Analyze Statement (d)
**Statement (d): \( Cu^+ \) is paramagnetic.**

- The atomic number of copper (Cu) is 29, and its electron configuration is \( [Ar] 3d^{10} 4s^1 \).
- When copper loses one electron to form \( Cu^+ \), the configuration becomes \( [Ar] 3d^{10} \).
- The \( 3d \) subshell is fully filled, meaning there are no unpaired electrons.
- A species with no unpaired electrons is diamagnetic, not paramagnetic.

**Conclusion:** Statement (d) is incorrect.

### Final Conclusion
The correct statements are:
- Statement (a) is correct.
- Statement (b) is correct.
- Statement (c) is incorrect.
- Statement (d) is incorrect.

Thus, the correct answer is option 3: A and B.

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