Ammonia contains three bonds where nitrogen is bonded to hydrogen. Nitrogen has a total of five valence electrons. This means that three of those electrons are involved in the bond formation with hydrogen and 2 electrons will be left unbonded. This will lead to a formation of a lone pair. Therefore, we can say that nitrogen has one lone pair of electrons.

Water contains 2 oxygen atoms bonded to hydrogen atoms. Oxygen contains 6 electrons in its valence orbitals which means that out of the 6 electrons, two electrons will be involved in the bonding with hydrogen. This means that 4 electrons will remain. For this reason, we can say that oxygen will have two lone pairs of electrons.

We also know that the presence of either a lone pair or a bond pair causes repulsions in a compound. That is there are repulsions between a lone pair and another lone pair of electrons, between a lone pair and a bond pair and between two bond pairs. This is because of the electron density that is involved in these bonds.

Therefore, we can say that the bond angle in ammonia is more than that of the bond angle of water. Therefore, we can conclude by saying that the assertion that even though central atom of both NH3 ​and H2O molecules are sp3 C hybridized, yet H−N−H bond angle is greater than that of H−O−H is true. And the reason, that is, nitrogen atom has a lone pair and oxygen atom has two lone pairs is true as well.

Therefore, both the assertion and reason is true and the reason is the correct explanation of the assertion

Within the cations layers ions are held together by strong electrovalent bonds. But these separated ion layers are linked by a relatively weak H-bond. The weaker H-bond links calcium ions in the intermediate region. Consequently, the gypsum can be readily cleaved and stretched along the layer of water molecules.

Anhydride has a completely ionic structure involving only calcium and sulphate ions.

The larger the dipole moment, the more polar.The lesser or 0 dipole moment, the molecule will be non- polar.

In NaCl, Sodium and Chloride ions have complete octets.

Hence, NaCl is a stable compound.

Ionic bond involves complete transfer of electrons as there occurs formation of ions called cation and anion therefore, there exists a huge electrostatic force of attraction which makes it a strong bond. For example, sodium chloride is formed by an ionic bond between sodium and chloride ions.

Covalent bond involves sharing of two or more outer shell electrons that can hold all biomolecules together. Shared electrons are difficult to give away because two elements together share the electrons and make the bond stronger. For example, water molecules have covalent bonds in them.

We know that bond strength is inversely proportional to bond length. Bond length of ionic bonds is less as compared to that of covalent bonds. So we can say that ionic bonds are stronger than covalent bonds. Ionic bond is formed when there is small ionisation whereas covalent bonding occurs when polarisation degree is high.

Since the presence of coulombic attraction between oppositely charged ions in ionic bonding leads to its higher stability, it is stronger than the covalent bonding. Hence, the correct option is (C).

The bond enthalpy in H—O—H is not same for both the O−H bonds.

Correct Reason: Because electronic charge on oxygen atom is different after breaking of one O−H bond.

Number of electrons NO+ =7+8−1=14
Number of electrons CN- =6+7+1=14
Bond order = 10-4/2 =3
Both are diamagnetic.