Give reasons for the following:

Options

A. `BeO` is used as a refractory material.
B. Beryllium halides are polymeric.
C. `Be(OH)_(2)` dissolves in `NaOH`, but `Ca(OH)_(2)` does not
D. On hydrolysis at room temperature, `Mg_(3)N_(2)` gives ammonia, whereas `MgCl_(2)` gives `HCl`.

Explanation

### Step-by-Step Solution:

**1. Beryllium oxide is used as a refractory material.**
- **Reason:** Beryllium oxide (BeO) is thermally stable and inert towards chemical reactions due to its high lattice enthalpy. The strong ionic bonds in BeO prevent it from dissociating into its constituent ions, which contributes to its stability at high temperatures. This makes BeO suitable for use as a refractory material, as it can withstand extreme heat without undergoing chemical changes.

**2. Beryllium halides are polymeric.**
- **Reason:** Beryllium halides, such as beryllium chloride (BeCl2), exhibit polymeric behavior because beryllium has an incomplete octet. To achieve a stable electronic configuration, beryllium atoms can form polymeric chains in the solid state. In the case of BeCl2, the polymeric structure is characterized by 4-electron 3-center (4e-3c) bonds, allowing the formation of a network structure that stabilizes the compound.

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