© Copyright 1995, R.Lanigan-O'Keeffe, Sydney Australia. Not for copying without permission.

THE DISTRIBUTION OF
NATURALLY OCCURRING ISOTOPES
AND THE MEAN PROPERTIES
OF THE CHEMICAL ELEMENTS.

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Mechanically unsound neutron numbers appear in bold, have less than 5% abundance for all conditions.
Element names appearing in bold have abundancy greater than 99%.
Element names appearing in Italics show mechanically unsound properties.

Table of Naturally Occurring Isotopes by Atomic Weight

Elprons = 1 Hydrogen H Mean Atomic Mass = 1.00797
Negativity = 1.4 V Ionisation = 13.598 V, 1318 kJ mol-1
Atomic Radii I = 1.45 C = 0.37
Melting -259 C Boiling -253 C

Elprons = 2 Helium He Mean Atomic Mass = 4.0026
Negativity = na Ionisation = 24.587 V, 2379 kJ mol-1
Atomic Radii I= na C = na
Melting -270 C Boiling -269 C

Elprons = 3 Lithium Li Mean Atomic Mass = 6.939
Negativity = 0.98 V Ionisation = 5.39 V, 526 kJ mol-1
Atomic Radii I = 0.78 C = 1.33
Melting 180 C Boiling 1330 C

Elprons = 4 Beryllium Be Mean Atomic Mass = 9.012
Negativity = 1.57 Ionisation = 9.32 V, 906 kJ mol-1
Atomic Radii I = 0.31 C = 0.89
Melting 1280 C Boiling 2480 C

End of Core Layer

Elprons = 5 Boron B Mean Atomic Mass = 10.811
Negativity = 2.04 Ionisation = 8.30 V, 807 kJ mol-1
Atomic Radii I = 0.20 C = 0.80
Melting (2030) C Boiling 3900 C

Elprons = 6 Carbon C Mean Atomic Mass = 12.01115
Negativity = 2.55 Ionisation = 11.26 V, 1093 kJ mol-1
Atomic Radii I = na C = 0.77
Melting 3730 C Boiling 4830 C

Elprons = 7 Nitrogen N Mean Atomic Mass = 14.0067
Negativity = 3.04 Ionisation = 14.53 V, 1407 kJ mol-1
Atomic Radii I = na C = 0.74
Melting -210 C Boiling -196 C

Elprons = 8 Oxygen O Mean Atomic Mass = 15.9994
Negativity = 3.44 Ionisation = 13.62 V, 1320 kJ mol-1
Atomic Radii I = 1.40 C = 0.74
Melting -219 C Boiling -183 C

Elprons = 9 Fluorine F Mean Atomic Mass = 18.998
Negativity = 3.98 Ionisation = 17.42 V, 1687 kJ mol-1
Atomic Radii I = 1.36 C = 0.72
Melting -220 C Boiling -188 C

Elprons = 10 Neon Ne Mean Atomic Mass = 20.183 Inert
Negativity = na Ionisation = 21.56 V, 2087 kJ mol-1
Atomic Radii I = na C = na
Melting -249 C Boiling -246 C

Elprons = 11 Sodium Na Mean Atomic Mass = 22.9898
Negativity = 0.93 Ionisation = 5.14 V, 502 kJ mol-1
Atomic Radii I = 0.98 C = 1.57
Melting 98 C Boiling 892 C

Elprons = 12 Magnesium Mg Mean Atomic Mass = 24.312
Negativity = 1.31 Ionisation = 7.65 V, 744 kJ mol-1
Atomic Radii I = 0.65 C = 1.36
Melting 650 C Boiling 1110 C

End of first intermediate level

Elprons = 13 Aluminium Al Mean Atomic Mass = 26.982
Negativity = 1.61 Ionisation = 5.99 V, 584 kJ mol-1
Atomic Radii I = 0.50 C = 1.25
Melting 660 C Boiling 2450 C

Elprons = 14 Silicon Si Mean Atomic Mass = 28.086
Negativity = 1.19 Ionisation = 8.15 V, 793 kJ mol-1
Atomic Radii I = 0.43 C = 1.17
Melting 1410 C Boiling 2680 C

Elprons = 15 Phosphorous P Mean Atomic Mass = 30.979
Negativity = 2.19 Ionisation = 10.49 V, 1018 kJ mol-1
Atomic Radii I = na C = 1.10
Melting 44 C Boiling 280 C

Elprons = 16 Sulphur S Mean Atomic Mass = 32.064
Negativity = 2.58 Ionisation = 10.36 V, 1006 kJ mol-1
Atomic Radii I = 1.84 C = 1.04
Melting 113 C Boiling 445 C

Elprons = 17 Chlorine Cl Mean Atomic Mass = 35.453
Negativity = 3.16 Ionisation = 12.97 V, 1257 kJ mol-1
Atomic Radii I = 1.81 C = 0.99
Melting -101 C Boiling -35 C

Elprons = 18 Argon Ar or A Mean Atomic Mass = 39.948 Inert
Negativity = na Ionisation = 15.75 V, 1527 kJ mol-1
Atomic Radii I = na C = na
Melting -189 C Boiling -186 C

Elprons = 19 Potassium K Mean Atomic Mass = 39.102
Negativity = 0.82 Ionisation = 4.34 V, 425 kJ mol-1
Atomic Radii I = 1.33 C = 2.03
Melting 64 C Boiling 760 C

Elprons = 20 Calcium Ca Mean Atomic Mass = 40.08
Negativity = 1.00 Ionisation = 6.11V, 596 kJ mol-1
Atomic Radii I = 0.99 C = 1.74
Melting 838 C Boiling 1490 C

End of first layer.

Begins 5 + 5 intermediate layer

Elprons = 21 Scandium Sc Mean Atomic Mass = 44.956
Negativity = 1.36 Ionisation = 6.54 V, 637 kJ mol-1
Atomic Radii I = 0.81 C = 1.44
Melting 1540 C Boiling 2730 C

Elprons = 22 Titanium Ti Mean Atomic Mass = 47.90
Negativity = 1.54 Ionisation = 6.82 V, 664 kJ mol-1
Atomic Radii I = 0.68 C =1.32
Melting 1670 C Boiling 3260 C

Elprons = 23 Vanadium V Mean Atomic Mass = 50.942
Negativity = 1.63 Ionisation = 6.74 V, 656 kJ mol-1
Atomic Radii I = na C = 1..22
Melting 1900 C Boiling 3450 C

Elprons = 24 Chromium Cr Mean Atomic Mass = 51.996
Negativity = 1.66 Ionisation = 6.77 V, 659 kJ mol-1
Atomic Radii I = na C = 1.17
Melting 1900 C Boiling 2642 C

Elprons = 25 Manganese Mn Mean Atomic Mass = 54.938
Negativity = 1.55 Ionisation = 7.43 V, 724 kJ mol-1
Atomic Radii I = na C = 1.17
Melting 1250 C Boiling 2110 C

Elprons = 26 Iron Fe Mean Atomic Mass = 55.847
Negativity = 1.83 Ionisation = 7.87 V, 766 kJ mol-1
Atomic Radii I = 0.60 C = 1.16
Melting 1540 C Boiling 3000 C

Elprons = 27 Cobalt Co Mean Atomic Mass = 54.938
Negativity = 1.88 Ionisation = 7.86 V, 764 kJ mol-1
Atomic Radii I = na C = 1.16
Melting 1490 C Boiling 2900 C

Elprons = 28 Nickel Ni Mean Atomic Mass = 58.71
Negativity = 1.91 Ionisation = 7.64 V, 743 kJ mol-1
Atomic Radii I = na C = 1.15
Melting 1450 C Boiling 2730 C

Elprons = 29 Copper Cu Mean Atomic Mass = 63.54
Negativity = 1.9 Ionisation = 7.86 V, 752 kJ mol-1
Atomic Radii I = 0.96 C =1.17
Melting 1083 C Boiling 2600 C

Elprons = 30 Zinc Zn Mean Atomic Mass = 65.37
Negativity = 1.65 Ionisation = 9.39 V, 913 kJ mol-1
Atomic Radii I = 0.74 C =1.25
Melting 419 C Boiling 906 C

Ends 5 + 5 Intermediate layer

Start of Second Core 4 +4

Elprons = 31 Gallium Ga Mean Atomic Mass = 69.72
Negativity = 1.81 Ionisation = 6.00 V, 585 kJ mol-1
Atomic Radii I = 0.62 C =1.25
Melting 30 C Boiling 2400 C

Elprons = 32 Germanium Ge Mean Atomic Mass = 72.59
Negativity = 2.01 Ionisation = 7.88 V, 768 kJ mol-1
Atomic Radii I = 0.53 C =1.22
Melting 937 C Boiling 2830 C

Elprons = 33 Arsenic As Mean Atomic Mass = 74.922
Negativity = 2.18 Ionisation = 9.8 V, 953 kJ mol-11
Atomic Radii I = na C =1.21
Melting 817* C Boiling (s) 613 C

Elprons = 34 Selenium Se Mean Atomic Mass = 78.96
Negativity = 2.55 Ionisation = 9.75 V, 947 kJ mol-1
Atomic Radii I = 1.98 C =1.17
Melting 217 C Boiling 685 C

Elprons = 35 Bromine Br Mean Atomic Mass = 79.909
Negativity = 2.96 Ionisation = 6.00 V, 1146 kJ mol-1
Atomic Radii I = 1.95 C =1.14
Melting -7 C Boiling 58 C

Elprons = 36 Krypton Kr Mean Atomic Mass = 83.80 Inert
Negativity = na Ionisation = 14.00 V, 1357 kJ mol-1
Atomic Radii I = na C = na
Melting -157 C Boiling -152 C

Elprons = 37 Rubidium Rb Mean Atomic Mass = 85.47
Negativity = 0.82 Ionisation = 4.18 V, 409 kJ mol-1
Atomic Radii I = 1.48 C = 2.16
Melting 39 C Boiling 688 C

Elprons = 38 Strontium Sr Mean Atomic Mass = 87.62
Negativity = 0.95 Ionisation = 6.00 V, 556 kJ mol-1
Atomic Radii I = 1.13 C =1.91
Melting 770 C Boiling 1380 C

End of level 1 of Layer 2

Start of 5 + 5 Intermediate level 2 of Layer 2

Elprons = 39 Yttrium Y Mean Atomic Mass = 88.905
Negativity = 1.22 Ionisation = 6.25 V, 622 kJ mol-1
Atomic Radii I = 0.93 C =1.61
Melting 1500 C Boiling 2930 C

Elprons = 40 Zirconium Zr Mean Atomic Mass = 91.22
Negativity = 1.33 Ionisation = 6.95 V, 666 kJ mol-1
Atomic Radii I = 0.74 C =1.45
Melting 1850 C Boiling 3580 C

Elprons = 41 Niobium Nb Mean Atomic Mass = 92.906
Negativity = 1.6 Ionisation = 6.77 V, 670 kJ mol-1
Atomic Radii I = na C =1.34
Melting 2420 C Boiling 4900 C

Elprons = 42 Molybdenum Mo Mean Atomic Mass = 95.94
Negativity = 2.16 Ionisation = 7.1 V, 691kJ mol-1
Atomic Radii I = na C =1.29
Melting 2610 C Boiling 5560 C

Elprons = 43 Technetium Tc Mean Atomic Mass = (99)
Negativity = 1.19 Ionisation = 7.28 V, 708 kJ mol-1
Atomic Radii I = na C = na
Melting 2140 C Boiling (4600 C)

Elprons = 44 Rutherenium Ru Mean Atomic Mass = 101.07
Negativity = 2.2 Ionisation = 7.36 V, 717 kJ mol-1
Atomic Radii I = na C =1.24
Melting 2300 C Boiling 3900 C

Elprons = 45 Rhodium Rh Mean Atomic Mass = 102.905
Negativity = 2.28 Ionisation = 7.46 V, 726 kJ mol-1
Atomic Radii I = na C =1.25
Melting 1970 C Boiling 3730 C

Elprons = 46 Palladium Pd Mean Atomic Mass = 106.4
Negativity = 2.2 Ionisation = 8.33 V, 811 kJ mol-1
Atomic Radii I = na C =1.28
Melting 1550 C Boiling 3125 C

Elprons = 47 Silver Ag Mean Atomic Mass = 107.870
Negativity = 1.93 Ionisation = 7.57 V, 737 kJ mol-1
Atomic Radii I = 1.26 C =1.34
Melting 961 C Boiling 2210 C

Elprons = 48 Cadmium Cd Mean Atomic Mass = 112.40
Negativity = 1.69 Ionisation = 8.99 V, 874 kJ mol-1
Atomic Radii I = 0.97 C =1.41
Melting 321 C Boiling 765 C

End of Intermediate layer

Start of 4 + 4 Core level 2, Layer 2

Elprons = 49 Indium In Mean Atomic Mass = 114.82
Negativity = 1.78 Ionisation = 5.79 V, 565 kJ mol-1
Atomic Radii I = 0.81 C =1.50
Melting 156 C Boiling 2000 C

Elprons = 50 Tin Sn Mean Atomic Mass = 118.69
Negativity = 1.96 Ionisation = 7.34 V, 715 kJ mol-1
Atomic Radii I = 0.71 C =1.41
Melting 217 C Boiling 685 C

Elprons = 51 Antimony Sb Mean Atomic Mass = 121.75
Negativity = 2.05 Ionisation = 8.64 V, 840 kJ mol-1
Atomic Radii I = na C =1.41
Melting 631 C Boiling 1380 C

Elprons = 52 Tellurium Te Mean Atomic Mass = 127.60
Negativity = 2.1 Ionisation = 9.01 V, 876 kJ mol-1
Atomic Radii I = 2.21 C =1.37
Melting 450 C Boiling 1390 C

Elprons = 53 Iodine I Mean Atomic Mass = 126.904
Negativity = 2.66 Ionisation = 10.45 V, 1015 kJ mol-1
Atomic Radii I = 2.16 C =1.33
Melting 114 C Boiling 183 C

Elprons = 54 Xenon Xe Mean Atomic Mass = 131.30 Inert
Negativity = na Ionisation = 12.13 V, 1177 kJ mol-1
Atomic Radii I = na C = na
Melting -112 C Boiling -108 C

Elprons = 55 Caesium Cs Mean Atomic Mass = 132.905
Negativity = 0.79 Ionisation = 3.89 V, 382 kJ mol-1
Atomic Radii I = 1.69 C = 2.35
Melting 29 C Boiling 690 C

Elprons = 56 Barium Ba Mean Atomic Mass = 137.34
Negativity = 0.89 Ionisation = 12.13 V, 509 kJ mol-1
Atomic Radii I = 1.35 C =1.98
Melting 714 C Boiling 1640 C

Layer 2 completed

Start of 7 + 7 Intermediate level, layer 3

Elprons = 57 Lanthanum La Mean Atomic Mass = 138.91
Negativity = 1.1 Ionisation = 5.61 V, 544 kJ mol-1
Atomic Radii I = 1.22 C = 1.41
Melting 920 C Boiling 3470 C

Elprons = 58 Cerium Ce Mean Atomic Mass = 140.12
Negativity = 1.12 Ionisation = 5.47 V, 534 kJ mol-1
Atomic Radii I = 1.01 C = 1.65
Melting 795 C Boiling 3470 C

Elprons = 59 Praseodymium Pr Mean Atomic Mass = 140.907
Negativity = 1.13 Ionisation = 5.42 V, 529 kJ mol-1
Atomic Radii I = na C = 1.65
Melting 935 C Boiling 3130 C

Elprons = 60 Neodymium Nd Mean Atomic Mass = 144.24
Negativity = 1.14 Ionisation = 5.49 V, 536 kJ mol-1
Atomic Radii I = na C =1.64
Melting 1020 C Boiling 3030 C

Elprons = 61 Promethium Pm Mean Atomic Mass = 145
Negativity = 1.2 Ionisation = 5.55 V, 542 kJ mol-1
Atomic Radii I = na C = na
Melting (1030 C) Boiling (2730 C)

Elprons = 62 Samarium Sm Mean Atomic Mass = 150.35
Negativity = 1.17 Ionisation = 5.63 V, 549 kJ mol-1
Atomic Radii I = na C =1.66
Melting 1070 C Boiling 1900 C

Elprons = 63 Europium Eu Mean Atomic Mass = 151.96
Negativity = 1.13 Ionisation = 5.67 V, 553 kJ mol-1
Atomic Radii I = na C =1.85
Melting 826 C Boiling 1440 C

Elprons = 64 Gadolinium Gd Mean Atomic Mass = 157.25
Negativity = 1.2 Ionisation = 6.14 V, 598 kJ mol-1
Atomic Radii I = na C =1.61
Melting 1310 C Boiling 3000 C

Elprons = 65 Terbium Tb Mean Atomic Mass = 158.924
Negativity = 1.2 Ionisation = 5.85 V, 570 kJ mol-1
Atomic Radii I = na C =1.59
Melting 1360 C Boiling 2800 C

Elprons = 66 Dysprosium Dy Mean Atomic Mass = 162.50
Negativity = 1.22 Ionisation = 5.93 V, 578 kJ mol-1
Atomic Radii I = na C =1.59
Melting 1410 C Boiling 2600 C

Elprons = 67 Holmium Ho Mean Atomic Mass = 164.930
Negativity = 1.23 Ionisation = 6.02 V, 586 kJ mol-1
Atomic Radii I = na C =1.58
Melting 1460 C Boiling 2600 C

Elprons = 68 Erbium Er Mean Atomic Mass = 167.26
Negativity = 1.24 Ionisation = 6.10 V, 595 kJ mol-1
Atomic Radii I = na C =1.57
Melting 1500 C Boiling 2900 C

Elprons = 69 Thulium Tm Mean Atomic Mass = 168.934
Negativity = 1.25 Ionisation = 6.18 V, 601 kJ mol-1
Atomic Radii I = na C =1.56
Melting 1550 C Boiling 1730 C

Elprons = 70 Ytterbium Yb Mean Atomic Mass = 173.04
Negativity = 1.1 Ionisation = 6.25 V, 610 kJ mol-1
Atomic Radii I = na C =1.70
Melting 824 C Boiling 1430 C

End of 7 + 7 Intermediate level, Layer 3

Start of 5 + 5 Intermediate level 1, Layer 3

Elprons = 71 Lutetium Lu Mean Atomic Mass = 174.97
Negativity = 1.27 Ionisation = 5.43 V, 530 kJ mol-1
Atomic Radii I = na C =1.56
Melting 1650 C Boiling 3330 C

Elprons = 72 Hafnium Hf Mean Atomic Mass = 178.49
Negativity = 1.3 Ionisation = 7.0 V, 680 kJ mol-1
Atomic Radii I = na C =1.44
Melting 2000 C Boiling 5400 C

Elprons = 73 Tantalum Ta Mean Atomic Mass = 180.948
Negativity = 1.5 Ionisation = 7.88 V, 767 kJ mol-1
Atomic Radii I = na C =1.34
Melting 3000 C Boiling 5430 C

Elprons = 74 Tungsten W Mean Atomic Mass = 183.85
Negativity = 2.36 Ionisation = 7.98 V, 776 kJ mol-1
Atomic Radii I = na C =1.30
Melting 3410 C Boiling 5930 C

Elprons = 75 Rhenium Re Mean Atomic Mass = 186.2
Negativity = 1.9 Ionisation = 7.87 V, 766 kJ mol-1
Atomic Radii I = na C =1.28
Melting 3180 C Boiling 5630 C

Elprons = 76 Osmium Os Mean Atomic Mass = 190.2
Negativity = 2.2 Ionisation = 8.70 V, 850 kJ mol-1
Atomic Radii I = na C =1.26
Melting 3000 C Boiling 5500 C

Elprons = 77 Iridium Ir Mean Atomic Mass = 192.2
Negativity = 2.2 Ionisation = 9.1 V, 880 kJ mol-1
Atomic Radii I = na C =1.26
Melting 2450 C Boiling 4500 C

Elprons = 78 Platinum Pt Mean Atomic Mass = 195.09
Negativity = 2.28 Ionisation = 9.00 V, 870 kJ mol-1
Atomic Radii I = na C =1.29
Melting 1770 C Boiling 3825 C

Elprons = 79 Gold Au Mean Atomic Mass = 196.967
Negativity = 2.54 Ionisation = 9.22 V, 896 kJ mol-1
Atomic Radii I = 1.37 C =1.34
Melting 1063 C Boiling 2970 C

Elprons = 80 Mercury Hg Mean Atomic Mass = 200.59
Negativity = 2.00 Ionisation = 10.43 V, 1013 kJ mol-1
Atomic Radii I = 1.10 C =1.44
Melting -39 C Boiling 357 C

End of 5 + 5 Intermediate level 1, Layer 3

Start of 4 + 4 Core level 1, Layer 3

Elprons = 81 Thallium Tl Mean Atomic Mass = 204.37
Negativity = 2.04 Ionisation = 6.11 V, 596 kJ mol-1
Atomic Radii I = 0.95 C =1.55
Melting 303 C Boiling 1460 C

Elprons = 82 Lead Pb Mean Atomic Mass = 207.19
Negativity = 2.33 Ionisation = 7.42 V, 722 kJ mol-1
Atomic Radii I = 0.84 C =1.54
Melting 327 C Boiling 1740 C

Elprons = 83 Bismuth Bi Mean Atomic Mass = 208.980
Negativity = 2.02 Ionisation = 7.29 V, 710 kJ mol-1
Atomic Radii I = na C =1.52
Melting 271 C Boiling 1560 C

Elprons = 84 Polonium Po Mean Atomic Mass = 210
Negativity = 2 Ionisation = 8.42 V, 818 kJ mol-1
Atomic Radii I = na C =1.52
Melting 254 C Boiling 962 C

Elprons = 85 Astatine At Mean Atomic Mass = 210
Negativity = 2.2 Ionisation = na
Atomic Radii I = na C =na
Melting 302 C Boiling 335 C

Elprons = 86 Radon Em , Rn Mean Atomic Mass = 222 Inert
Negativity = na Ionisation = 10.75 V, 1043 kJ mol-1
Atomic Radii I = na C = na
Melting -71 C Boiling -62 C

Elprons = 87 Francium Fr Mean Atomic Mass = 223
Negativity = 0.7 Ionisation = na
Atomic Radii I = na C =na
Melting (27 C) Boiling (680 C)

Elprons = 88 Radium Ra Mean Atomic Mass = 226.05
Negativity = 0.9 Ionisation = 5.28 V, 516 kJ mol-1
Atomic Radii I = na C =na
Melting 700 C Boiling 1530 C

End of level 1, Layer 3

Start of 7 + 7 Intermediate level 2, Layer 3