The number of unpaired electrons in `1s^(2) 2s^(2) 2p^(3)` is

Options

A. 1
B. 2
C. 3
D. 5

Answer

To determine the number of unpaired electrons in the electronic configuration `1s^(2) 2s^(2) 2p^(3)`, we can follow these steps:

### Step 1: Identify the Electron Configuration
The given electron configuration is `1s^(2) 2s^(2) 2p^(3)`. This indicates the distribution of electrons in the various atomic orbitals.

### Step 2: Fill the Orbitals
1. **1s Orbital**: The `1s` orbital can hold a maximum of 2 electrons. In this case, it has `2` electrons (1s²), which means both are paired.
2. **2s Orbital**: The `2s` orbital also holds a maximum of 2 electrons. Here, it has `2` electrons (2s²), which are also paired.
3. **2p Orbital**: The `2p` orbital can hold a maximum of 6 electrons. In this case, it has `3` electrons (2p³). According to Hund's rule, these electrons will occupy separate orbitals before pairing up. Thus, each of the three electrons will occupy one of the three available p orbitals (2p_x, 2p_y, 2p_z) singly.

### Step 3: Count the Unpaired Electrons
- In the `1s` orbital: 0 unpaired electrons (2 paired)
- In the `2s` orbital: 0 unpaired electrons (2 paired)
- In the `2p` orbital: 3 unpaired electrons (each in separate orbitals)

### Conclusion
Adding the unpaired electrons from all orbitals, we find:
- Total unpaired electrons = 0 (from 1s) + 0 (from 2s) + 3 (from 2p) = **3 unpaired electrons**.

Thus, the answer is **3**.