He Helium Index

Helium (He) Element Properties

Atomic Mass	4.002602
Atomic Number	2
Name Origins	Greek, helios = "sun."
Year Discovered	1895
Discovery Credits	Isolated in 1895 by Sir William Ramsay at London, UK, and independently by P. T. Cleve and N. A. Langlet at Uppsala, Sweden.
Remarks	Colorless, odorless gas. Unreactive chemically. Used in deep-sea diving, weather balloons, and low temperature research instruments. Most natural sources of helium come from natural gas deposits where He is present from the alpha particle decay of heavy radioisotopes of U and Th and their daughter products.
References	Emsley, J., 1991; THE ELEMENTS : Sec. Ed., Clarendon Press, Oxford, 251 p.
See Also	WebElements, ChemiCool

**Naturally Occurring Isotopes**
Symbol	Isotope Mass	Isotope Nuclide Number	Isotope Number	Natural Abundance	Half-life	Half-life Units	Decay Mode	Decay Mode MeV	Decay Mode %
He	3.01603	3	2	0.0001%		Stable
He	4.0026	4	2	99.9999%		Stable

Group	1	2		3	4	5	6	7	8	9	10	11	12	13	14	15	16	17	18
Period
1	1 H																		2 He
2	3 Li	4 Be												5 B	6 C	7 N	8 O	9 F	10 Ne
3	11 Na	12 Mg												13 Al	14 Si	15 P	16 S	17 Cl	18 Ar
4	19 K	20 Ca		21 Sc	22 Ti	23 V	24 Cr	25 Mn	26 Fe	27 Co	28 Ni	29 Cu	30 Zn	31 Ga	32 Ge	33 As	34 Se	35 Br	36 Kr
5	37 Rb	38 Sr		39 Y	40 Zr	41 Nb	42 Mo	43 Tc	44 Ru	45 Rh	46 Pd	47 Ag	48 Cd	49 In	50 Sn	51 Sb	52 Te	53 I	54 Xe
6	55 Cs	56 Ba	*	71 Lu	72 Hf	73 Ta	74 W	75 Re	76 Os	77 Ir	78 Pt	79 Au	80 Hg	81 Tl	82 Pb	83 Bi	84 Po	85 At	86 Rn
7	87 Fr	88 Ra	**	103 Lr	104 Rf	105 Db	106 Sg	107 Bh	108 Hs	109 Mt	110 Ds
-
*Lanthanides			*	57 La	58 Ce	59 Pr	60 Nd	61 Pm	62 Sm	63 Eu	64 Gd	65 Tb	66 Dy	67 Ho	68 Er	69 Tm	70 Yb
**Actinides			**	89 Ac	90 Th	91 Pa	92 U	93 Np	94 Pu	95 Am	96 Cm	97 Bk	98 Cf	99 Es	100 Fm	101 Md	102 No