Find the number of unpaired electrons present in phosphorus (atomic no.15), chromium (atomic no. 24) and copper (atomic no. 29) after writing their orbital electronic configurations.

Explanation

To find the number of unpaired electrons in phosphorus, chromium, and copper, we will first write their orbital electronic configurations and then determine the number of unpaired electrons in each case.

### Step 1: Write the electronic configuration of phosphorus (atomic number 15)

1. The atomic number of phosphorus is 15, which means it has 15 electrons.
2. The electronic configuration is built up according to the Aufbau principle:
- 1s² (2 electrons)
- 2s² (2 electrons)
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