Group 2 Elements

To determine which of the given hydroxides is amphoteric, we need to understand what amphoteric substances are. An amphoteric substance can react with both acids and bases. In the context of hydroxides, only certain metal hydroxides possess this property.

Looking at the options provided:

1. : Strontium hydroxide is a strong base and does not exhibit amphoteric behavior. It primarily reacts with acids.
2. : Calcium hydroxide is also a strong base and reacts with acids. It does not show amphoteric properties.
3. : Magnesium hydroxide is a weak base and it mainly reacts with acids, not considered amphoteric.
4. : Beryllium hydroxide is amphoteric. It can react with acids to form beryllium salts and with bases to form beryllate ions.

The correct answer is as it can react with both acids and bases. The reactions are as follows:

• Reaction with acid:
• Reaction with base:

This dual ability to react with both acids and bases makes an amphoteric hydroxide.

The question asks about the structural forms of beryllium chloride (BeCl₂) in solid state and vapor phase. To answer this correctly, we must understand the chemistry behind the structure of BeCl₂ in different states.

Solid State: In the solid state, BeCl₂ forms a polymeric chain structure. This is due to the fact that beryllium has a small size and high polarizing power, which causes it to form covalent bonds with chlorine atoms. Each beryllium atom is bridged to two chlorine atoms, forming a linear chain.

Vapor Phase: In the vapor phase, BeCl₂ exists as a dimer, (BeCl₂)₂. This occurs because, in the gaseous state, the molecule seeks to minimize energy, leading to the formation of a stable dimeric form with two Be atoms bridged by two Cl atoms.

Hence, the structures of beryllium chloride in solid state and vapor phase are chain and dimer, respectively.

Thus, the correct answer is: Chain and dimer, respectively.