Whichof the following substances is covalently bonded ?

Options

A. KBr
B. Sodium chloride
C. Solid neon
D. Copper

Answer

To determine which of the given substances is covalently bonded, we can analyze each option based on the nature of the bonds formed between the atoms.

### Step-by-Step Solution:

1. **Identify the Options**: The options provided are KBr, NaCl, solid neon, and copper.

2. **Analyze KBr**:
- KBr consists of potassium (K) and bromine (Br).
- Potassium has a low electronegativity, while bromine has a higher electronegativity.
- The difference in electronegativity is significant, leading to the formation of an ionic bond.
- **Conclusion**: KBr is not covalently bonded; it is ionic.

3. **Analyze NaCl**:
- NaCl consists of sodium (Na) and chlorine (Cl).
- Similar to KBr, sodium has a lower electronegativity compared to chlorine.
- The large difference in electronegativity results in the formation of an ionic bond.
- **Conclusion**: NaCl is not covalently bonded; it is ionic.

4. **Analyze Solid Neon**:
- Neon is a noble gas with a complete valence shell (1s² 2s² 2p⁶).
- Noble gases are chemically inert and do not typically form bonds, as they do not need to gain, lose, or share electrons.
- **Conclusion**: Solid neon does not form any bonds, neither ionic nor covalent.

5. **Analyze Copper**:
- Copper (Cu) has an electronic configuration of [Ar] 3d¹⁰ 4s¹.
- It has one electron in its outermost shell that can be shared with other atoms.
- This sharing of electrons indicates the formation of a covalent bond.
- **Conclusion**: Copper can form covalent bonds by sharing its outer electron.

6. **Final Conclusion**:
- Among the given options, copper is the only substance that can form covalent bonds.

### Answer:
The substance that is covalently bonded is **Copper**.