Question

$NaH$ is an example of
A: Electron-rich hydride
B: Molecular hydride
C: Saline hydride
D: Metallic hydride

Answer 1

Hint : $NaH$ is sodium hydride. This is an alkali metal hydride. Examples of alkali metal are lithium, sodium, potassium etc. Hydrides are hydrogen anions. Anions are chemical species which possess negative charge.

Complete step by step solution :
Sodium hydride is obtained by reaction of metallic sodium with hydrogen.
$2Na + {H_2}\xrightarrow{{}}2NaH$
Sodium hydride $NaH$ has a structure like sodium chloride $(NaCl)$ crystal structure. Each sodium ion $(N{a^ + })$ is surrounded by six hydrides having octahedral geometry. Hydrides are anions of hydrogen which are compounds of hydrogen with more electronegative elements. As the name suggests electron rich hydrides are hydrides which have excess electrons which are present in the form of lone pairs. Elements of group $15,16,17$ form such compounds examples are ammonia $(N{H_3})$ water $({H_2}O)$ hydrochloric acid $(HCl)$ etc. Molecular hydrides are also called covalent hydride; these are usually volatile compounds. Group $13$ elements form such hydride. Saline hydrides are also called ionic hydride. Metals having electronegativity lower than hydrogen form such hydride. All elements of group $1$ and group $2$ when heated form ionic hydride. Metallic hydrides are also called interstitial hydride. d and f block elements on heating with dihydrogen under pressure form hydrides. Hydrogen atoms are small in size due to which they occupy some space in metallic lattice which causes distortion without any change in type that is why such hydrides are called interstitial hydrides. As we have read above that group $1$ elements form ionic hydrides and sodium is also group $1$ element therefore sodium hydride is saline hydride. So the answer to this question is option C, which is saline hydride.
Additional information: sodium hydride is insoluble in organic solvent. It is used as a drying agent for laboratory chemicals. As it releases hydrogen gas it is being explored as a hydrogen storage agent in fuel cell vehicles.

Note : Hydrides are compounds or ions which have hydrogen atoms bonded to less electronegative elements. Different types of hydrides are distinguished on the basis of different types of bonds such as ionic, metallic or covalent whereas polymeric hydride is identified on the basis of structure.