A121818 Average of atomic weights of all isotopes of first n elements, rounded to nearest integer.

1, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 20, 21, 22, 23, 24, 25, 26, 27, 28, 30, 31, 32, 33, 34, 35, 36, 38, 39, 40, 41, 43, 44, 45, 46, 47, 49, 50, 51, 52, 53, 55, 56, 57, 58, 60, 61, 62, 63, 65, 66, 67, 69, 70, 71, 72, 74, 75, 76, 78, 79, 80, 81, 83, 84, 85

Offset: 1

Author

Jonathan Vos Post, Aug 26 2006

Keywords

• nonn
• fini
• less

Comments

This is poorly defined, even with the caveats of A007656, for the highest atomic numbers (with no stable isotopes) and the values given are with respect to Earth, as different planets presumably have slightly different isotopic ratios.

Examples

			a(1) = round(1.0080/1) = 1 = mean atomic weight of hydrogen (protium + deuterium + tritium).
a(2) = round((1.0080+4.003)/2) = round(5.011/2) = round(2.5055) = 3.
		

Crossrefs

Cf. A007656, A070217, A121291.

Programs

Mathematica

Needs["Miscellaneous`ChemicalElements`"]
Table[ Round[ Sum[ AtomicWeight(AT)Elements[[i]], {i, n}]/n], {n, 111}] (* Robert G. Wilson v, Sep 02 2006 *)

Extensions

More terms from Robert G. Wilson v, Sep 02 2006

Edited by N. J. A. Sloane, Sep 14 2006