Difference between revisions of "Selenium"
(Added xerography and essential trace element) |
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group=16 | | group=16 | | ||
period=4 | | period=4 | | ||
| − | phase=Solid | + | phase=Solid | |
series=Non-metals | | series=Non-metals | | ||
| − | density=(gray) 4.81 g/cm3(alpha) 4.39 g/cm3(vitreous) 4.28 g/cm3 | | + | density=(gray) 4.81 g/cm3<BR/>(alpha) 4.39 g/cm3<BR/>(vitreous) 4.28 g/cm3 | |
melts=494K,<BR/>221°C,<BR/>430°F | | melts=494K,<BR/>221°C,<BR/>430°F | | ||
boils=958K,<BR/>685°C,<BR/>1265°F | | boils=958K,<BR/>685°C,<BR/>1265°F | | ||
Latest revision as of 12:37, 27 April 2011
| Selenium | |
|---|---|
| Se | |
| In situ availability: | |
| Necessity: | |
| Atomic number: | 34 |
| Atomic mass: | 78.96 |
| group: | 16 |
| period: | 4 |
| normal phase: | Solid |
| series: | Non-metals |
| density: | (gray) 4.81 g/cm3 (alpha) 4.39 g/cm3 (vitreous) 4.28 g/cm3 |
| melting point: | 494K, 221°C, 430°F |
| boiling point: | 958K, 685°C, 1265°F |
| P ← S → Cl | |
| As ← Se → Br | |
| Sb ← Te → I | |
| Atomic radius (pm): | 115 |
| Bohr radius (pm): | 103 |
| Covalent radius (pm): | 116 |
| Van der Waals radius (pm): | 190 |
| ionic radius (pm): | (-2) 198 |
| 1st ion potential (eV): | 9.75 |
| Electron Configuration | |
| 1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p4 | |
| Electrons Per Shell | |
| 2, 8, 18, 6 | |
| Electronegativity: | 2.55 |
| Electron Affinity: | 2.02 |
| Oxidation states: | +/-2, 4, 6 |
| Magnetism: | ? |
| Crystal structure: | Hexagonal |
Selenium is a Non-metal in group 16. It was named after the Moon.
It has a Hexagonal crystalline structure.
This element has 6 stable isotopes: 74, 76, 77, 78, 80, and 82. It is a semiconductor whose resistance varies by exposure to light. This property is used in xerography (Greek for dry writing).Photocopying
Selenium (Se) is an essential micronutrient for many organisms, including plants, animals and humans. However, it is toxic if taken in excess. Intake of more than 400 micrograms per day can lead to selenosis in humans. It is used in some anti-dandruff shampoos to control dandruff by killing fungi on the scalp.
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