Question

Give examples of ionic hydride, molecular hydrides, interstitial hydride, electron precise hydride.

Answer 1

Hint: The term hydride refers to an anion of hydrogen. Hydrogen generally forms a proton, but when it forms a compound with an element with lower electronegativity, it forms a hydride.

Complete step by step answer:
- Let us start this question by understanding the term hydride. ‘Hydride’ is formally the anion of hydrogen, i.e. when hydrogen makes a compound with an element of lesser electronegativity. It is represented as ${{H}^{-}}$. As we can see, in hydrides, the oxidation number of hydrogen is -1.

When hydrogen combines with different elements it forms different type of hydride –

1. Ionic hydride: When hydrogen forms a compound with group IA elements, it forms an ionic hydride.
   Example – Lithium Hydride (LiH), Sodium Hydride (NaH), Potassium hydride (KH).
2. Molecular hydride: These kinds of hydrides are formed by electron-rich compounds (generally p-block elements).
   Example – Water$({{H}_{2}}O)$, Ammonia$(N{{H}_{3}})$
3. Interstitial hydride: These are also known as metallic halides. This type of halide is generally formed by d-block elements.
   Example – Zinc Hydride$(Zn{{H}_{2}})$, Scandium Hydride $(Sc{{H}_{2}})$
4. Electron precise hydride: The compounds which have the exact number of electrons to form normal covalent bonds form electron precise halides. Group 14 compounds form this type of element.
   Example – Methane $(C{{H}_{4}})$

Additional Information: Electronegativity of hydrogen is 2.2. Fluorine is the most electronegative element of the periodic table, with an electronegativity about 3.98.

Note: In group 6, Chromium is the only element to form a hydride. Elements from Group 7, 8 and 9 of the periodic table do not form hydride. This is also known as hydride gap. Hydride gap occurs because the electronegativity of these elements is higher than that of hydrogen.