Answer to Question #37306 in Inorganic Chemistry for emmanuel kofi mensah

Question

1.explain why boron in the +3 state forms no ionic compound.
2.explain why,at ordinary temperature Carbon dioxide is a gas whilst silicon dioxide is a solid.
3.explain why Hydrogen is comparatively un reactive.

Answer 1

1. The electronegativity of boron is not low enough and its atomic radius is quite small, therefore it cannot form the ionic compounds with cations B3+. However the anions with boron 3+ are the most common compounds of boron, such as sodium tetraborate.
2. Carbon dioxide exists as single molecules CO2. The interactions between molecules in CO2 is low enough, so it exists as gas. However the SiO2 forms the 3-dimensional lattice - a big molecular crystal with strong covalent bonds between adjacent atoms. This lattice cannot be easily destroyed, so SiO2 exists as crystalline solid.
3. The bond energy H-H is very large. Therefore Hydrogen will react only with aggressive oxidants, such as molecular fluorine, or powerfull reductants, such as alkaline metals.