M= 1 and n = 2
( m+ n = 1 +2 = 3)
rate = K [A] [B]^2
0.2 = K * 3 * 3 ^2
0.2 = K * 3 * 9
K = 0.2 / 27
K = 7.408 * 10 ^ -3 m^-2 s^-1
Iodine has 7 valence electrons. It needs therefore only 1 electron to be stable this is why it is so reactive.
Volume is the amount of space an object takes up