Which out of the following molecules have covalent bonds
`(i)CaCl_(2)(ii)NH_(3)(iii) MgO(iv)PCl_(5)` ?

Answer

To determine which of the given molecules have covalent bonds, we will analyze each molecule one by one.

### Step 1: Analyze CaCl₂ (Calcium Chloride)
- Calcium (Ca) has 2 valence electrons, while Chlorine (Cl) has 7 valence electrons.
- Calcium will lose its 2 electrons to form Ca²⁺, and each Chlorine will gain 1 electron to form Cl⁻.
- The bonding in CaCl₂ is due to the transfer of electrons from Calcium to Chlorine, resulting in ionic bonds.

**Conclusion for CaCl₂**: Contains ionic bonds, not covalent bonds.

### Step 2: Analyze NH₃ (Ammonia)
- Nitrogen (N) has 5 valence electrons, and each Hydrogen (H) has 1 valence electron.
- Nitrogen shares its three electrons with three Hydrogens, forming three covalent bonds.
- The structure of NH₃ is pyramidal, and the bonds are formed by sharing electrons.

**Conclusion for NH₃**: Contains covalent bonds.

### Step 3: Analyze MgO (Magnesium Oxide)
- Magnesium (Mg) has 2 valence electrons, and Oxygen (O) has 6 valence electrons.
- Magnesium will lose its 2 electrons to form Mg²⁺, and Oxygen will gain 2 electrons to form O²⁻.
- The bonding in MgO is due to the transfer of electrons from Magnesium to Oxygen, resulting in ionic bonds.

**Conclusion for MgO**: Contains ionic bonds, not covalent bonds.

### Step 4: Analyze PCl₅ (Phosphorus Pentachloride)
- Phosphorus (P) has 5 valence electrons, and each Chlorine (Cl) has 7 valence electrons.
- Phosphorus shares its five electrons with five Chlorine atoms, forming five covalent bonds.
- The structure of PCl₅ is trigonal bipyramidal, and the bonds are formed by sharing electrons.

**Conclusion for PCl₅**: Contains covalent bonds.

### Final Answer
The molecules that have covalent bonds are:
- NH₃ (Ammonia)
- PCl₅ (Phosphorus Pentachloride)

### Summary
- **CaCl₂**: Ionic bonds
- **NH₃**: Covalent bonds
- **MgO**: Ionic bonds
- **PCl₅**: Covalent bonds