Electronic data		Thermal data		Steric data
Shells: 2,8,18,6 Orbitals: [Ar] 3d10 4s2 4p4 Electronegativity: 2.5, 2.4 1. Ionization potential: 9.7524 eV 2. Ionization potential: 21.19 eV 3. Ionization potential: 30.82 eV Oxidation states: 6,4,-2 Electrical conductivity: 1.0e-12 10^6		Melting point: 217 °C Boiling point: 684.9 °C Specific heat: 0.32 J/gK Heat of fusion: 6.694 kJ/mol Heat of vaporization: 37.70 kJ/mol Thermal conductivity: 0.0204 W/cmK		Atomic radius: 1.22 Å Ionic radius: 0.50 Å () Covalent radius: 1.16 Å Atomic volume: 16.45 cm³/mol Density (293 K): 4.79 g/cm³ Crystal structure: Hexagonal

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Nuclide	Abundance [%]	Mass	Spin	Halflife	Decay mode	Decay tree
73Se	0	73	0	7.15h	-	View
74Se	0.87	73.9225	0	--	stable	--
75Se	0	74.923	0	119.78d	-	View
76Se	9.02	75.9192	0	--	stable	--
77Se	7.58	76.9199	1/2	--	stable	--
78Se	23.52	77.9173	0	--	stable	--
79Se	0	78.919	7/2	~6.5E04y	-	View
80Se	49.82	79.9165	0	--	stable	--
82Se	9.19	81.9167	0	--	stable	--

Legend

Name origin:	Greek: selênê (moon)
Description:	Soft metalloid similar to sulfur. Ranges from gray metallic to red glassy appearance.
Discovered by:	Jöns Berzelius
Year:	1818
Place:	Sweden
Sources:	Obtained from lead, copper and nickel refining. Conducts electricity when struck by light.
Use(s):	Light causes it to conduct electricity more easily. It is used in photoelectric cells, TV cameras, xerography machines and as a semiconductor in solar batteries and rectifiers. Also colors glass red.