Template:Infobox selenium

Selenium, ₃₄Se
Selenium
Pronunciation	/sɪˈliːniəm/ (sih-LEE-nee-əm)
Appearance	black an reid allotropes
Standard atomic weight Ar, std(Se)	78.971(8)
Selenium in the periodic cairt
	arsenic ← selenium → bromine
Atomic nummer (Z)	34
Group	group 16 (chalcogens)
Period	period 4
Block	p-block
Element category	Reactive nonmetal
Electron confeeguration	[Ar] 3d10 4s2 4p4
Electrons per shell	2, 8, 18, 6
Pheesical properties
Phase at STP	solit
Meltin pynt	494 K (221 °C, 430 °F)
Bylin pynt	958 K (685 °C, 1265 °F)
Density (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
Creetical pynt	1766 K, 27.2 MPa
Heat o fusion	(gray) 6.69 kJ/mol
Heat o vapourisation	95.48 kJ/mol
Molar heat capacity	25.363 J/(mol·K)
Atomic properties
Oxidation states	−2, −1, +1, +2, +3, +4, +5, +6 strangly acidic
Electronegativity	Pauling scale: 2.55
Atomic radius	empirical: 120 pm
Covalent radius	120±4 pm
Van der Waals radius	190 pm
	Colour lines in a spectral rangeSpectral lines o selenium
Ither properties
Naitural occurrence	primordial
Creestal structur	hexagonal
Speed o soond 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 orderin	diamagnetic
Young's modulus	10 GPa
Shear modulus	3.7 GPa
Bulk modulus	8.3 GPa
Poisson ratio	0.33
Mohs haurdness	2.0
Brinell haurdness	736 MPa
CAS Nummer	7782-49-2
History
Diskivery	Jöns Jakob Berzelius an Johann Gottlieb Gahn (1817)
First isolation	Jöns Jakob Berzelius an Johann Gottlieb Gahn (1817)
Main isotopes o selenium
γ	-
γ	-
	Decay modes in parentheses are predictit, but hae nae yet been observed
	view; talk; edit; \| references

style="text-align:left"\| data m.p. cat v
	in	calc from C	diff	report	ref
C	221	—	—
K	494	494	0
F	430	430	0
WD	392 !392 Fahrenheit				^[4]
input	C: 221, K: 494, F: 430
comment

style="text-align:left"\| data b.p. cat v
	in	calc from C	diff	report	ref
C	685	—	—
K	958	958	0
F	1265	1265	0
WD	1265 !1265 Fahrenheit				^[4]
input	C: 685, K: 958, F: 1265
comment

References

↑ Meija, Juris; et al. (2016). "Atomic weights of the elements 2013 (IUPAC Technical Report)". Pure and Applied Chemistry. 88 (3): 265–91. doi:10.1515/pac-2015-0305.
↑ Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth–Heinemann. ISBN 0080379419.
↑ Magnetic susceptibility of the elements and inorganic compounds, in Lide, D. R., ed. (2005). CRC Handbook of Chemistry and Physics (86th ed.). Boca Raton (FL): CRC Press. ISBN 0-8493-0486-5.
1 2 http://www.cdc.gov/niosh/npg/npgd0550.html.

[CIAAW2013-1] Meija, Juris; et al. (2016). "Atomic weights of the elements 2013 (IUPAC Technical Report)". Pure and Applied Chemistry. 88 (3): 265–91. doi:10.1515/pac-2015-0305.

[2] Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth–Heinemann. ISBN 0080379419.

[3] Magnetic susceptibility of the elements and inorganic compounds, in Lide, D. R., ed. (2005). CRC Handbook of Chemistry and Physics (86th ed.). Boca Raton (FL): CRC Press. ISBN 0-8493-0486-5.

[wikidata-b2fde376cb5c6133631af8f69b7abd716faa3924-v3-4] 1 2 http://www.cdc.gov/niosh/npg/npgd0550.html.

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