Indicate the number of unpaired electrons in:
a. `P, b. Si, c. Cr`,
d. `Fe, e. Kr`

Explanation

To determine the number of unpaired electrons in the given elements (Phosphorus, Silicon, Chromium, Iron, and Krypton), we will analyze their electronic configurations step by step.

### Step 1: Phosphorus (P)
- **Atomic Number**: 15
- **Electronic Configuration**: 1s² 2s² 2p⁶ 3s² 3p³
- **Analysis**:
- The 3p subshell has 3 electrons.
- The electron configuration of the p subshell can be represented as: ↑ ↑ ↑ (where each arrow represents an unpaired electron).
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