What is the formal charge on each atom in the tetrahydridoborate ion?

1 Answer
Mar 26, 2018

Answer:

Well, we normally represent sodium borohydride as #Na^+BH_4^-#...

Explanation:

...and since this is clearly NEUTRAL...we split the salt up in to #Na^+# and #BH_4^(-)# ions....

...for the tetrahedral borohydride ion....there are #4xxB-H# bonds....each hydrogen atom is associated with ONE electron, and is therefore neutral. On the other hand, the boron atom get 4 electrons from the #B-H# bonds, and there are two inner core electrons....six electrons in total. Since for boron, #Z=5#, given 5 nucular charges, and SIX electronic charges....the boron atom has a formal negative charge.

Borohydrides ACT as hydride transfer reagents in their reaction chemistry....i.e. #BH_4^(-)-=BH_3 + H^-#...they tend to be a bit milder reagents than aluminum hydrides...salts of #AlH_4^(-)#...