The number of neutrons present in the nuclei of H 11, H 12 and H 13 respectively are
1, 2, 3
0, 1, 2
0, 0, 1
1 in each
H 11→1e-,1p, no n
H 12→1e-,1p, 1 n
H 13→1e-,1p, 2 n