Selenium

Selenium, ₃₄Se

Selenium
Pípè	/sᵻˈliːniəm/ ​(sə-LEE-nee-əm)
Ìhànsójú	Black, gray, and red allotropes
Ìwúwo átọ̀mù Ar, std(Se)	78.971(8)
Selenium ní orí tábìlì àyè
Hydrogen Helium Lithium Beryllium Boron Carbon Nitrogen Oxygen Fluorine Neon Sodium Magnesium Aluminium Silicon Phosphorus Sulfur Chlorine Argon Potassium Calcium Scandium Titanium Vanadium Chromium Manganese Iron Cobalt Nickel Copper Zinc Gallium Germanium Arsenic Selenium Bromine Krypton Rubidium Strontium Yttrium Zirconium Niobium Molybdenum Technetium Ruthenium Rhodium Palladium Silver Cadmium Indium Tin Antimony Tellurium Iodine Xenon Caesium Barium Lanthanum Cerium Praseodymium Neodymium Promethium Samarium Europium Gadolinium Terbium Dysprosium Holmium Erbium Thulium Ytterbium Lutetium Hafnium Tantalum Tungsten Rhenium Osmium Iridium Platinum Gold Mercury (element) Thallium Lead Bismuth Polonium Astatine Radon Francium Radium Actinium Thorium Protactinium Uranium Neptunium Plutonium Americium Curium Berkelium Californium Einsteinium Fermium Mendelevium Nobelium Lawrencium Rutherfordium Dubnium Seaborgium Bohrium Hassium Meitnerium Darmstadtium Roentgenium Copernicium Nihonium Flerovium Moscovium Livermorium Tennessine Oganesson S ↑ Se ↓ Te arsenic ← selenium → bromine
Nọ́mbà átọ̀mù (Z)	34
Ẹgbẹ́	group 16 (chalcogens)
Àyè	àyè 4
Àdìpọ̀	Àdìpọ̀-p
Ẹ̀ka ẹ́límẹ́ntì	Reactive nonmetal
Ìtò ẹ̀lẹ́ktrọ́nù	[Ar] 3d10 4s2 4p4
Iye ẹ̀lẹ́ktrọ́nù lórí ìpele kọ̀ọ̀kan	2, 8, 18, 6
Àwọn ohun ìní ara
Ìfarahàn at STP	solid
Ìgbà ìyọ́	494 K ​(221 °C, ​430 °F)
Ígbà ìhó	958 K ​(685 °C, ​1265 °F)
Kíki (near r.t.)	(gray) 4.81 g/cm3 (alpha) 4.39 g/cm3 (vitreous) 4.28 g/cm3
when liquid (at m.p.)	3.99 g/cm3
Critical point	1766 K, 27.2 MPa
Heat of fusion	(gray) 6.69 kJ/mol
Heat of	95.48 kJ/mol
Molar heat capacity	25.363 J/(mol·K)
pressure P (Pa) 1 10 100 1 k 10 k 100 k at T (K) 500 552 617 704 813 958
Atomic properties
Oxidation states	−2, −1, +1, +2, +3, +4, +5, +6 Àdàkọ:Infobox element/symbol-to-oxidation-state/comment
Electronegativity	Pauling scale: 2.55
Atomic radius	empirical: 120 pm
Covalent radius	120±4 pm
Van der Waals radius	190 pm
Color lines in a spectral range Spectral lines of selenium
Other properties
Natural occurrence	primordial
Crystal structure	​hexagonal
Speed of sound thin rod	3350 m/s (at 20 °C)
Thermal expansion	(amorphous) 37 µm/(m·K) (at 25 °C)
Thermal conductivity	(amorphous) 0.519 W/(m·K)
Magnetic ordering	diamagnetic
Young's modulus	10 GPa
Shear modulus	3.7 GPa
Bulk modulus	8.3 GPa
Poisson ratio	0.33
Mohs hardness	2.0
Brinell hardness	736 MPa
CAS Number	7782-49-2
Main isotopes of selenium
Iso­tope Abun­dance Half-life (t1/2) Decay mode Pro­duct 72Se syn 8.4 d ε - 72As γ 0.046 - 74Se 0.87% 74Se is stable with 40 neutrons 75Se syn 119.779 d ε - 75As γ 0.264, 0.136, 0.279 - 76Se 9.36% 76Se is stable with 42 neutrons 77Se 7.63% 77Se is stable with 43 neutrons 78Se 23.78% 78Se is stable with 44 neutrons 79Se trace 2.95×105 y β− 0.151 79Br 80Se 49.61% 80Se is stable with 46 neutrons 82Se 8.73% 1.08×1020 y β−β− 2.995 82Kr