Mendeleev's Periodic Table > Se - Selenium

Se - Selenium

Selenium was discovered by J. J. Berzelius in 1817 in Sweden. Selenium can be prepared with either an amorphous or crystalline structure. Crystalline monoclinic selenium is deep red; crystalline hexagonal selenium, the most stable variety, is a metallic grey (see picture above). Elemental selenium is relatively nontoxic and is considered to be an essential trace element. However, hydrogen selenide (H₂Se) and other selenium compounds are extremely toxic, and resemble arsenic in their physiological reactions. Hydrogen selenide in a concentration of 1.5 ppm is intolerable to man. Selenium occurs in some soils in amounts sufficient to produce serious effects on animals feeding on plants such as locoweed (an American plant) grown in such soils.

Atomic number	-	34		Density	g/mL	4	.8
Atomic weight	u	78	.96	Melting point	K	494
Bonding radius	A	1	.16	Boiling point	K	958
Atomic radius	A	1	.22	Heat of vaporization	kJ/mol	37	.7
Ionization Potential	V	9	.752	Heat of fusion	kJ/mol	6	.694
Electronegativity	-	2	.55	Specific heat	J/gK	0	.32
The oxide is a strong acid.				Crystal are hexagonal.
Electron config. : [Ar] 3d¹⁰ 4s² 4p⁴

Isotopes of Se (Selenium):

MASS abundancy Halflife Particle, Energy Decay Product(s) Isotopic Mass	065 50 msec EC,14.100 MeV As-65 64.964680	067 107 msec EC/ECp,10.150 As-67/Ge-66 66.950090	068 35.5 sec EC,4.700 MeV As-68 67.941921	069 27.4 sec EC/ECp,6.780 As-69/Ge-68 68.939559
MASS abundancy Halflife Particle, Energy Decay Product(s) Isotopic Mass	070 41.1 min EC,2.400 MeV As-70 69.933504	071 4.74 min EC,4.800 MeV As-71 70.932270	072 8.40 da EC,4.356 MeV As-72 71.927112	073 7.15 hr EC,2.740 MeV As-73 72.926767
MASS abundancy Halflife Particle, Energy Decay Product(s) Isotopic Mass	074 0.89% Stable 73.922476	075 119.79 da EC,1.316 MeV As-75 74.922523	076 9.36% Stable 75.919214	077 7.63% Stable 76.919914
MASS abundancy Halflife Particle, Energy Decay Product(s) Isotopic Mass	078 23.78% Stable 77.917309	079 6.5E+5 yr B-,2.281 MeV Br-79 78.918499	080 49.61% Stable 79.916522	081 18.45 min B-,1.585 MeV Br-81 80.917992
MASS abundancy Halflife Particle, Energy Decay Product(s) Isotopic Mass	082 8.73% 1.08E+20 yr B-B-,2.995 Kr-82 81.916700	083 22.3 min B-,3.668 MeV Br-83 82.919119	084 3.1 min B-,1.830 MeV Br-84 83.918464	085 31.7 sec B-,6.182 MeV Br-85 84.922243
MASS abundancy Halflife Particle, Energy Decay Product(s) Isotopic Mass	086 15.3 sec B-,5.099 MeV Br-86 85.924276	087 5.29 sec B-/B-n,7.280 Br-87/Br-86 86.928523	088 1.53 sec B-/B-n,6.850 Br-88/Br-87 87.931432	089 0.41 sec B-/B-n,9.000 Br-89/Br-88 88.936016
MASS abundancy Halflife Particle, Energy Decay Product(s) Isotopic Mass	091 0.27 sec B-/B-n,10.700 Br-91/Br-90 90.945356