Which element is more likely to dissociate into its monatomic form at 3000 k. h or n. why?

H2

Explanation:

In the first place it is necessary to consider that these two elements will be their diatomic form initially, that is, H2 and N2.

first we should check the equilibrium constant Kp tables in this case at a temperature of 3000K

Value for dissociation reaction of H2  in Kp = -3.685

Value for dissociation reaction of N2 in Kp = -22.359

Equilibrium constant for H2 dissociation is higher than N2 dissociation. so for this comparation H2 is more likely to dissociate.