Question

why bf3 is negative and nh4 is positive?​

Answer 1

Answer:Hey friend here is your answer,

Using this method u can solve for all molecules . if u have any doubts ask me in the comments.

Method 2 :

1) NH4 +

no:of valence electrons of central atom (N) = 5

no:of atoms attached to central atom = 4

charge on the molecule =+1

hybridisation=1/2(5+4-(+1))=8/2=4

So its sp3.

2)BF4 -

no:of valence electrons of central atom (B) = 3

no:of atoms attached to central atom = 4

charge on the molecule = - 1

hybridisation=1/2(3+4-(-1)=8/2=4

So its sp3.

Explanation: