Which of the following atoms do not usually form bonds?

Options

A. Calcium
B. hydrogen
C. neon
D. oxygen

Explanation

To determine which of the following atoms do not usually form bonds, we need to analyze the electronic configurations and bonding tendencies of the given atoms. The atoms in question are Calcium, Hydrogen, Neon, and Oxygen.

### Step-by-Step Solution:

1. **Identify the Atoms**: The atoms we need to consider are Calcium (Ca), Hydrogen (H), Neon (Ne), and Oxygen (O).

2. **Understand Electron Configuration**:
- **Calcium (Ca)**: Atomic number 20. Its electronic configuration is [Ar] 4s². Calcium has 2 electrons in its outermost shell and tends to lose these electrons to achieve a stable configuration, thus it can form bonds.
- **Hydrogen (H)**: Atomic number 1. Its electronic configuration is 1s¹. Hydrogen has 1 electron and needs 1 more to achieve a stable configuration (duplet rule), so it can form bonds.
- **Neon (Ne)**: Atomic number 10. Its electronic configuration is 1s² 2s² 2p⁶. Neon has a complete outer shell (8 electrons in the valence shell), making it stable and unreactive. Therefore, Neon does not typically form bonds.
- **Oxygen (O)**: Atomic number 8. Its electronic configuration is 1s² 2s² 2p⁴. Oxygen has 6 electrons in its outer shell and needs 2 more to complete its octet, so it will form bonds.

3. **Conclusion**: Among the atoms listed, Neon is the only atom that does not usually form bonds due to its complete valence shell, which makes it stable and unreactive.

### Final Answer:
The atom that does not usually form bonds is **Neon (Ne)**.