Write the electronic configuration of chromium (Z = 24) and predict in it
(i) number of subshells
(ii) number of electrons in subshell having l = 0
(iii) number of electrons having `n + l` value equal to 3
(iv) number of electrons in highest value of n.

Answer

To solve the question regarding the electronic configuration of chromium (Z = 24) and to predict various properties, we will follow these steps:

### Step 1: Write the electronic configuration of chromium (Z = 24)

1. **Determine the expected configuration**:
- The expected order of filling the orbitals according to the Aufbau principle is:
- 1s², 2s², 2p⁶, 3s², 3p⁶, 4s², 3d⁴
- However, chromium has a unique configuration due to stability reasons.

2. **Actual electronic configuration**:
- The actual electronic configuration of chromium is:
- 1s², 2s², 2p⁶, 3s², 3p⁶, 4s¹, 3d⁵

### Step 2: Predict the number of subshells

- **Count the subshells**:
- The subshells present in the configuration are:
- 1s, 2s, 2p, 3s, 3p, 4s, 3d
- Total number of subshells = 7

### Step 3: Determine the number of electrons in the subshell having l = 0

- **Identify subshells with l = 0**:
- The subshells with l = 0 are the s subshells (1s, 2s, 3s, and 4s).
- Count the electrons:
- 1s² = 2 electrons
- 2s² = 2 electrons
- 3s² = 2 electrons
- 4s¹ = 1 electron
- Total = 2 + 2 + 2 + 1 = 7 electrons

### Step 4: Determine the number of electrons having n + l value equal to 3

- **Calculate n + l for each subshell**:
- 1s²: n=1, l=0 → n + l = 1 + 0 = 1 (discarded)
- 2s²: n=2, l=0 → n + l = 2 + 0 = 2 (discarded)
- 2p⁶: n=2, l=1 → n + l = 2 + 1 = 3 (accepted, 6 electrons)
- 3s²: n=3, l=0 → n + l = 3 + 0 = 3 (accepted, 2 electrons)
- 3p⁶: n=3, l=1 → n + l = 3 + 1 = 4 (discarded)
- 4s¹: n=4, l=0 → n + l = 4 + 0 = 4 (discarded)
- 3d⁵: n=3, l=2 → n + l = 3 + 2 = 5 (discarded)

- **Total number of electrons with n + l = 3**:
- From 2p⁶: 6 electrons
- From 3s²: 2 electrons
- Total = 6 + 2 = 8 electrons

### Step 5: Determine the number of electrons in the highest value of n

- **Identify the highest value of n**:
- The highest principal quantum number (n) in the configuration is 4 (from 4s).
- Count the electrons in the 4s subshell:
- 4s¹ = 1 electron

### Final Answers

1. **Electronic configuration of chromium**: 1s², 2s², 2p⁶, 3s², 3p⁶, 4s¹, 3d⁵
2. **Number of subshells**: 7
3. **Number of electrons in subshell having l = 0**: 7
4. **Number of electrons having n + l value equal to 3**: 8
5. **Number of electrons in highest value of n**: 1