Question

All of the following are solids at room temperature. Classify them as molecular, ionic, network, or metallic. (a) Potassium \((\mathrm{K}), \mathrm{mp}=64{ }^{\circ} \mathrm{C}\) (b) Potassium chloride \((\mathrm{KCl}), \mathrm{mp}=770{ }^{\circ} \mathrm{C}\) (c) Red phosphorus \((\mathrm{P}), \mathrm{mp}=590{ }^{\circ} \mathrm{C}\) (d) Boron triiodide \(\left(\mathrm{BI}_{3}\right), \mathrm{mp}=50{ }^{\circ} \mathrm{C}\)

Short answer

(a) Potassium (K): Metallic (b) Potassium chloride (KCl): Ionic (c) Red phosphorus (P): Network (d) Boron triiodide (BI3): Molecular

Step-by-step solution

(a) Classify Potassium (K)

Potassium (K) is a metallic element, and as such, its bonding is metallic. Therefore, Potassium should be classified as metallic.

(b) Classify Potassium chloride (KCl)

Potassium chloride (KCl) is an ionic compound, formed by the transfer of an electron from potassium (an alkali metal) to chlorine (a halogen). The bonding in KCl is ionic; hence, it should be classified as an ionic solid.

(c) Classify Red phosphorus (P)

Red phosphorus (P) consists of phosphorus atoms connected in a network structure. Since P is a non-metal and forms a network structure, it should be classified as a network solid.

(d) Classify Boron triiodide (BI3)

Boron triiodide (BI3) is a covalently bonded compound composed of one boron atom and three iodine atoms. Covalently bonded compounds are usually molecular and can be classified as molecular solids.

Key concepts

Metallic Solid

Imagine a structure where metal atoms bond together by sharing a