The number of protons in an isotope atom does not change but the number of neutrons does. The iron atom has about twenty-eight isotopes. Such as 45Fe, 46Fe, 47Fe, 48Fe, 49Fe, 50Fe, 51Fe, 52Fe, 53Fe, 54Fe, 55Fe, 56Fe, 57Fe, 58Fe, 59Fe, 60Fe, 61Fe, 62Fe, 63Fe, 64Fe, 65Fe, 66Fe, 67Fe, 68Fe, 69Fe, 70Fe, 71Fe and 72Fe.
Among the isotopes, 54Fe (Observationally Stable), 56Fe, 57Fe, and 58Fe are stable and formed naturally. The remaining isotopes of iron are highly unstable and their half-lives are very short.
Isotope Mass number (A) Atomic number (Z) Neutron number = A – Z
45Fe 45.01458 26 19
46Fe 46.00081 26 20
47Fe 46.99289 26 21
48Fe 47.98050 26 22
49Fe 48.97361 26 23
50Fe 49.96299 26 24
51Fe 50.956820 26 25
52Fe 51.948114 26 26
53Fe 52.9453079 26 27
54Fe 53.9396090 26 28
55Fe 54.9382934 26 29
56Fe 55.9349363 26 30
57Fe 56.9353928 26 31
58Fe 57.9332744 26 32
59Fe 58.9348755 26 33
60Fe 59.934072 26 34
61Fe 60.936745 26 35
62Fe 61.936767 26 36
63Fe 62.94037 26 37
64Fe 63.9412 26 38
65Fe 64.94538 26 39
66Fe 65.94678 26 40
67Fe 66.95095 26 41
68Fe 67.95370 26 42
69Fe 68.95878 26 43
70Fe 69.96146 26 44
71Fe 70.96672 26 45
71Fe 71.96962 26 46