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Compare Oxygen vs Selenium

Comparing Oxygen (O) and Selenium (Se). Atomic numbers 8 and 34 with atomic masses 15.999 u and 78.972 u, classified as nonmetal and nonmetal. Below: a side-by-side comparison of their physical, atomic, electron-configuration and historical properties, including density, melting and boiling points, ionization energies, oxidation states and discovery history.

vs
O
Oxygen
#8
Se
Selenium
#34

Periodic properties of the elements

OxygenSelenium
SymbolOSe
Atomic number834
Group1616
Period24
Blockpp
Element categoryNonmetalNonmetal

Physical properties

OxygenSelenium
Phase at STPGasSolid
Density1.429 g/cm34.81 g/cm3
Atomic weight15.999 u78.9718 u
Melting point54.36 K
-218.79 °C
-361.822 °F		494 K
220.85 °C
429.53 °F
Boiling point90.188 K
-182.962 °C
-297.3316 °F		958 K
684.85 °C
1264.73 °F

Atomic properties

OxygenSelenium
Electronegativity (Pauling Scale)3.442.55
Electron affinity140.976 kJ/mol194.959 kJ/mol
Oxidation states−2, −1, 0, +1, +2
()		−2, −1, +1, +2, +3, +4, +5, +6
(a strongly acidic oxide)
Ionization energies
  1. 1313.9 kJ/mol
  2. 3388.3 kJ/mol
  3. 5300.5 kJ/mol
  4. 7469.2 kJ/mol
  5. 10989.5 kJ/mol
  6. 13326.5 kJ/mol
  7. 71330 kJ/mol
  8. 84078 kJ/mol
  1. 941 kJ/mol
  2. 2045 kJ/mol
  3. 2973.7 kJ/mol
  4. 4144 kJ/mol
  5. 6590 kJ/mol
  6. 7880 kJ/mol
  7. 14990 kJ/mol

Electron configuration

OxygenSelenium
Shorthand configuration[He] 2s2 2p4 [Ar] 3d10 4s2 4p4
Full configuration1s2 2s2 2p4 1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p4
Electrons per shell2, 62, 8, 18, 6

History

OxygenSelenium
DiscoveryCarl Wilhelm Scheele, Joseph Priestley (1774)Jöns Jakob Berzelius, Johan Gottlieb Gahn (1817)
First isolationJöns Jakob Berzelius, Johan Gottlieb Gahn (1817)
Named byAntoine Lavoisier (1777)
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