
Selenium (Se) is a chemical element of the periodic table, located in the group 16 and the period 4, and has the atomic number 34. It is a red powder or black reactive nonmetal, whose name comes from the Greek word “selene”, which means Moon. It is a member of the chalcogen group.
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– p block |
FAQs on Selenium Element
Selenium |
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‣ What does selenium look like? Appearance: grey metallic-looking, red, and vitreous black (not pictured) allotropes |
‣ Who discovered selenium? When was selenium discovered? Discovery and first isolation: Jons Jakob Berzelius and Johann Gottlieb Gahn (1817) |
‣ Where is selenium located on the periodic table?![]() Location: Selenium is found in the fourth row of the periodic table below the sulfur element. |
‣ What is selenium’s atomic number? Atomic number (Z): 34 |
‣ What is the symbol for selenium? Symbol: Se |
‣ What is the atomic weight of selenium? Standard atomic weight: 78.971 |
‣ What is the block of selenium? Block: p-block |
‣ What group is selenium in on the periodic table? Group: 16 (chalcogens) |
‣ Which period is selenium on the periodic table? Period: 4 |
‣ What is the atomic radius of selenium (atomic number 34)? Atomic radius: empirical: 120 pm |
‣ Selenium covalent radius: 120±4 pm |
‣ Selenium Van der Waals radius: 190 pm |
‣ What is the melting point of selenium? Melting point: 494 K (221 °C, 430 °F) |
‣ What is the boiling point of selenium? Boiling point: 958 K (685 °C, 1265 °F) |
‣ Selenium critical point: 1766 K, 27.2 MPa |
‣ How many electron shells does selenium have? Electrons per shell: 2, 8, 18, 6 |
‣ What is the ground state electron configuration of selenium? Electron configuration: [Ar] 3d10 4s2 4p4 |
‣ What is the ionization energy of selenium? Ionization energies: 1st: 941.0 kJ/mol 2nd: 2045 kJ/mol 3rd: 2973.7 kJ/mol |
‣ What is the phase of selenium at room temperature? Phase (at r.t): solid |
‣ What is the density of selenium? 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 |
‣ Selenium magnetic ordering: diamagnetic |
‣ Selenium natural occurrence: primordial |
‣ What is the oxidation state of selenium? Oxidation state: 0, -2, +4, +6 |
‣ What’s the electronegativity of selenium? Electronegativity: Pauling scale: 2.55 |
‣ Selenium poisson’s ratio: 0.33 |
‣ Selenium heat of fusion: gray: 6.69 kJ/mol |
‣ Selenium heat of vaporization: 95.48 kJ/mol |
‣ Selenium molar heat capacity: 25.363 J/(mol K) |
‣ Selenium molar magnetic susceptibility: -25.0 × 10-6 cm3/mol (298 K) |
‣ Speed of sound in selenium: 3350 m/s (at 20 °C) |
‣ Selenium crystal structure: hexagonal |
‣ Thermal expansion of selenium: amorphous: 37 µm/(m.K) (at 25 °C) |
‣ Thermal conductivity of selenium: amorphous: 0.519 W/(m.K) |
‣ What is the hardness of selenium? Mohs hardness: 2.0 Brinell hardness: 736 MPa |
‣ Young’s modulus of selenium: 10 GPa |
‣ Shear modulus of selenium: 3.7 GPa |
‣ Bulk modulus of selenium: 8.3 GPa |
‣ Selenium CAS number: 7782-49-2 |
‣ Selenium vapor pressure
Vapor pressure | ||||||
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P (Pa) | 1 | 10 | 100 | 1 k | 10 k | 100 k |
at T (K) | 500 | 552 | 617 | 704 | 813 | 958 |
‣ How many isotopes does selenium have?
Main isotopes of selenium | ||||
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Isotope | Abundance | Half-life (t1/2) | Decay mode | Product |
72Se | syn | 8.4 d | ε γ | 72As – |
74Se | 0.86 % | stable | ||
75Se | syn | 119.8 d | ε γ | 75As – |
76Se | 9.23 % | stable | ||
77Se | 7.60 % | stable | ||
78Se | 23.69 % | stable | ||
79Se | trace | 3.27 × 105 y | β– | 79Br |
80Se | 49.80 % | stable | ||
82Se | 8.82 % | 1.08 × 1020 y | β–β– | 82Kr |
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