NI3 is called Triiodoamine or nitrogen triiodide. First we need to count the total number of valence electrons. We just add the valence electrons of each atoms involved.
N = 5
I = 7 x 3
Next, we have to assign the central atom; In this case it is N.
Now we have to connect the atoms and form a bond. we can form three N-I bonds
I - N - I
Finally, we have to distribute The remaining electrons on Br and N provided that it follows the octet rule.
.. .. ..
: I - N - I :
: I :
NI3 has a similar structure with NH3. But the size of I makes the molecule nearly flat. It is still a polar molecule but has been found to be insoluble in water. Bond angle of which is a little bit greater than 109.5 degrees.