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 need to analyze each option based on the type of bonding that occurs between the elements involved.

### Step-by-Step Solution:

1. **Understand Covalent Bonding**:
- A covalent bond is formed by the sharing of electrons between two nonmetals.

2. **Identify the Bonding Types**:
- **Ionic Bond**: Formed by the complete transfer of electrons between a metal and a nonmetal.
- **Covalent Bond**: Formed by the sharing of electrons between two nonmetals.

3. **Analyze Each Option**:
- **Option 1: KBr (Potassium Bromide)**:
- Potassium (K) is a metal, and bromine (Br) is a nonmetal.
- Since this bond is between a metal and a nonmetal, it forms an ionic bond.
- **Conclusion**: Not covalently bonded.

- **Option 2: NaCl (Sodium Chloride)**:
- Sodium (Na) is a metal, and chlorine (Cl) is a nonmetal.
- This also forms an ionic bond due to the metal-nonmetal pairing.
- **Conclusion**: Not covalently bonded.

- **Option 3: Solid Neon (Ne)**:
- Neon is a noble gas.
- Noble gases typically do not form bonds as they have a complete valence shell. They are held together by weak van der Waals forces.
- **Conclusion**: Not covalently bonded.

- **Option 4: Copper (Cu)**:
- Copper is a metal, but it can share its electrons.
- The electronic configuration of copper is [Ar] 3d^10 4s^1, indicating that it has one electron in the outermost shell that can be shared.
- While copper primarily forms metallic bonds, under certain conditions, it can participate in covalent bonding by sharing its outer electron.
- **Conclusion**: Can form covalent bonds.

4. **Final Answer**:
- The substance that is covalently bonded among the options is **Copper (Cu)**, which is option number 4.