Question

Which of these is not a covalent hydride?
a. Ammonia
b. Ethyne
c. Hydrochloric acid gas
d. NaH

Answer 1

NaH is an ionic compound and an ionic hydride.

Answer 2

is this question is your real concern or you just want to gain score?

Answer 3

When answering this question you should consider electronegativity of the atoms involved in the molecule.

http://honorschemistrycyhs.wikispaces.com/file/view/enchart.gif/210725276/568x398/enchart.gif

The higher the electronegativity the stronger the atom holds onto its electrons, this is relevant because ionic bonding is essentially the giving of an electron to one atom and the loss of an electron to another, covalent on the other hand is sharing (note sharing is not always equal between atoms).

If you see a group 13 to 17 element in a molecule with a group 1 or 2 element then you can pretty much assume that it posses an ionic bond.

Answer 4

Sodium has a relatively weak electronegativity compared to Hydrogen, thus hydrogen will just steal the electron.

Note when I stated:

"If you see a group 13 to 17 element in a molecule with a group 1 or 2 element then you can pretty much assume that it posses an ionic bond."

Hydrogen is the exception to this rule.

Also the trend I posted you should note that the higher the number the higher the electronegativity, also note that those numbers are abstract, based on an experimental method and should not be remembered just remember the trend which is,

http://www.shodor.org/unchem-old/basic/period/periodictabledraft14.gif

Answer 5

If you know this trend chemistry becomes easier

Answer 6

@moradi312

In the future just guide to the answer never give the answer directly unless it is really the only option or you explain on how you reached it.

Answer 7

I'm not trying to be jerk, it is just this sites code of conduct.

Answer 8

@Australopithecus
thanks for your advise.you're right.