N2 (g) + __ H2 (g) --> _NH3 When the reaction above is completely balanced, the coefficient for hydrogen (H2) will be: *

3

Explanation:

left side has 2 N so right side must have a 2 which means 6 H on right side so to get 6 on left you have a coef. of 3 to make 6 H

atomic mass = 39

number of neutrons = 20

number of protons= 19

electronic configuration = 1s2 2s2 2p6 3s2 3p6 4s1

the number of electron in first shell = 2

number of electrons in n=3 shell = 8