Se Selenium
Element Information, Facts, Properties, Trends, Uses, Comparison with other elements
Selenium is a chemical element with symbol Se and atomic number 34. It is a nonmetal with properties that are intermediate between those of its periodic table column-adjacent chalcogen elements sulfur and tellurium. It rarely occurs in its elemental state in nature, or as pure ore compounds.
It belongs to group 16 of the periodic table having trivial name chalcogens.
Selenium Facts
Read key information and facts about element Selenium
| Name | Selenium |
| Atomic Number | 34 |
| Atomic Symbol | Se |
| Atomic Weight | 78.96 |
| Phase | Solid |
| Color | Gray |
| Appearance | black, red, and gray (not pictured) allotropes |
| Classification | Other Nonmetal |
| Group in Periodic Table | 16 |
| Group Name | oxygen family |
| Period in Periodic Table | period 4 |
| Block in Periodic Table | p -block |
| Electronic Configuration | [Ar] 3d10 4s2 4p4 |
| Electronic Shell Structure (Electrons per shell) | 2, 8, 18, 6 |
| Melting Point | 494 K |
| Boiling Point | 958 K |
| CAS Number | CAS7782-49-2 |
How to Locate Selenium on Periodic Table
Periodic table is arranged by atomic number, number of protons in the nucleus which is same as number of electrons. The atomic number increases from left to right. Periodic table starts at top left ( Atomic number 1) and ends at bottom right (atomic number 118). Therefore you can directly look for atomic number 34 to find Selenium on periodic table.
Another way to read periodic table and locate an element is by using group number (column) and period number (row). To locate Selenium on periodic table look for cross section of group 16 and period 4 in the modern periodic table.
Selenium History
The element Selenium was discovered by J. Berzelius and G. Gahn in year 1817 in Sweden. Selenium was first isolated by J. Berzelius and G. Gahn in 1817. Selenium derived its name from the Greek selene, meaning 'moon'.
While working with lead they discovered a substance that they thought was tellurium, but realized after more investigation that it is different.
Selenium Presence: Abundance in Nature and Around Us
The table below shows the abundance of Selenium in Universe, Sun, Meteorites, Earth's Crust, Oceans and Human Body.
| ppb by weight (1ppb =10^-7 %) | ppb by atoms (1ppb =10^-7 %) | |
|---|---|---|
| Abundance in Universe | 30 | 0.5 |
| Abundance in Sun | - | - |
| Abundance in Meteorites | 13000 | 2900 |
| Abundance in Earth's Crust | 50 | 10 |
| Abundance in Oceans | 0.45 | 0.035 |
| Abundance in Humans | 50 | 4 |
Crystal Structure of Selenium
The solid state structure of Selenium is Simple Monoclinic.
The Crystal structure can be described in terms of its unit Cell. The unit Cells repeats itself in three dimensional space to form the structure.
Unit Cell Parameters
The unit cell is represented in terms of its lattice parameters, which are the lengths of the cell edges Lattice Constants (a, b and c)
| a | b | c |
|---|---|---|
| 905.4 pm | 908.3 pm | 1160.1 pm |
and the angles between them Lattice Angles (alpha, beta and gamma).
| alpha | beta | gamma |
|---|---|---|
| π/2 | 1.58493 | π/2 |
The positions of the atoms inside the unit cell are described by the set of atomic positions ( xi, yi, zi) measured from a reference lattice point.
The symmetry properties of the crystal are described by the concept of space groups. All possible symmetric arrangements of particles in three-dimensional space are described by the 230 space groups (219 distinct types, or 230 if chiral copies are considered distinct.
| Space Group Name | P121/c1 |
| Space Group Number | 14 |
| Crystal Structure | Simple Monoclinic |
| Number of atoms per unit cell |
The number of atoms per unit cell in a simple cubic, face-centered cubic and body-centred cubic are 1,4,2 respectively.
Selenium Atomic and Orbital Properties
Selenium atoms have 34 electrons and the electronic shell structure is [2, 8, 18, 6] with Atomic Term Symbol (Quantum Numbers) 3P2.
| Atomic Number | 34 |
| Number of Electrons (with no charge) | 34 |
| Number of Protons | 34 |
| Mass Number | 79 |
| Number of Neutrons | 45 |
| Shell structure (Electrons per energy level) | 2, 8, 18, 6 |
| Electron Configuration | [Ar] 3d10 4s2 4p4 |
| Valence Electrons | 4s2 4p4 |
| Valence (Valency) | 6 |
| Main Oxidation States | -2, 2, 4, 6 |
| Oxidation States | -2, -1, 0, 1, 2, 3, 4, 5, 6 |
| Atomic Term Symbol (Quantum Numbers) | 3P2 |
Bohr Atomic Model of Selenium - Electrons per energy level
| n | s | p | d | f |
|---|
Ground State Electronic Configuration of Selenium - neutral Selenium atom
Abbreviated electronic configuration of Selenium
The ground state abbreviated electronic configuration of Neutral Selenium atom is [Ar] 3d10 4s2 4p4. The portion of Selenium configuration that is equivalent to the noble gas of the preceding period, is abbreviated as [Ar]. For atoms with many electrons, this notation can become lengthy and so an abbreviated notation is used. This is important as it is the Valence electrons 4s2 4p4, electrons in the outermost shell that determine the chemical properties of the element.
Unabbreviated electronic configuration of neutral Selenium
Complete ground state electronic configuration for the Selenium atom, Unabbreviated electronic configuration
1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p4
Electrons are filled in atomic orbitals as per the order determined by the Aufbau principle, Pauli Exclusion Principle and Hund’s Rule.
Atomic Structure of Selenium
Selenium atomic radius is 103 pm, while it's covalent radius is 116 pm.
| Atomic Radius Calculated | 103 pm (1.03 Å) |
| Atomic Radius Empirical | 115 pm (1.15 Å) |
| Atomic Volume | 16.385 cm3/mol |
| Covalent Radius | 116 pm (1.16 Å) |
| Van der Waals Radius | 190 pm |
| Neutron Cross Section | 11.7 |
| Neutron Mass Absorption | 0.0056 |
Atomic Spectrum of Selenium
Selenium Chemical Properties: Selenium Ionization Energies and electron affinity
The electron affinity of Selenium is 195 kJ/mol.
| Valence | 6 |
| Electronegativity | 2.55 |
| ElectronAffinity | 195 kJ/mol |
Ionization Energy of Selenium
Refer to table below for Ionization energies of Selenium
| Ionization energy number | Enthalpy - kJ/mol |
|---|---|
| 1st | 941 |
| 2nd | 2045 |
| 3rd | 2973.7 |
| 4th | 4144 |
| 5th | 6590 |
| 6th | 7880 |
| 7th | 14990 |
Selenium Physical Properties
Refer to below table for Selenium Physical Properties
| Density | 4.819 g/cm3(when liquid at m.p density is $3.99 g/cm3) |
| Molar Volume | 16.385 cm3/mol |
Elastic Properties
| Young Modulus | 10 |
| Shear Modulus | 3.7 GPa |
| Bulk Modulus | 8.3 GPa |
| Poisson Ratio | 0.33 |
Hardness of Selenium - Tests to Measure of Hardness of Element
| Mohs Hardness | 2 MPa |
| Vickers Hardness | - |
| Brinell Hardness | 736 MPa |
Selenium Electrical Properties
Selenium is Conductor of electricity. Refer to table below for the Electrical properties ofSelenium
| Electrical Conductivity | - |
| Resistivity | - |
| Superconducting Point | - |
Selenium Heat and Conduction Properties
| Thermal Conductivity | 0.52 W/(m K) |
| Thermal Expansion | - |
Selenium Magnetic Properties
| Magnetic Type | Diamagnetic |
| Curie Point | - |
| Mass Magnetic Susceptibility | -4e-9 m3/kg |
| Molar Magnetic Susceptibility | -3.16e-10 m3/mol |
| Volume Magnetic Susceptibility | -0.0000193 |
Optical Properties of Selenium
| Refractive Index | 1.000895 |
Acoustic Properties of Selenium
| Speed of Sound | 3350 m/s |
Selenium Thermal Properties - Enthalpies and thermodynamics
Refer to table below for Thermal properties of Selenium
| Melting Point | 494 K (220.85°C, 429.53000000000003 °F) |
| Boiling Point | 958 K (684.85°C, 1264.73 °F) |
| Critical Temperature | 1766 K |
| Superconducting Point | - |
Enthalpies of Selenium
| Heat of Fusion | 5.4 kJ/mol |
| Heat of Vaporization | 26 kJ/mol |
| Heat of Combustion | - |
Selenium Isotopes - Nuclear Properties of Selenium
Selenium has 30 isotopes, with between 65 and 94 nucleons. Selenium has 5 stable naturally occuring isotopes.
Isotopes of Selenium - Naturally occurring stable Isotopes: 74Se, 76Se, 77Se, 78Se, 80Se.
| Isotope | Z | N | Isotope Mass | % Abundance | T half | Decay Mode |
|---|---|---|---|---|---|---|
| 65Se | 34 | 31 | 65 | Synthetic | ||
| 66Se | 34 | 32 | 66 | Synthetic | ||
| 67Se | 34 | 33 | 67 | Synthetic | ||
| 68Se | 34 | 34 | 68 | Synthetic | ||
| 69Se | 34 | 35 | 69 | Synthetic | ||
| 70Se | 34 | 36 | 70 | Synthetic | ||
| 71Se | 34 | 37 | 71 | Synthetic | ||
| 72Se | 34 | 38 | 72 | Synthetic | ||
| 73Se | 34 | 39 | 73 | Synthetic | ||
| 74Se | 34 | 40 | 74 | 0.89% | Stable | N/A |
| 75Se | 34 | 41 | 75 | Synthetic | ||
| 76Se | 34 | 42 | 76 | 9.37% | Stable | N/A |
| 77Se | 34 | 43 | 77 | 7.63% | Stable | N/A |
| 78Se | 34 | 44 | 78 | 23.77% | Stable | N/A |
| 79Se | 34 | 45 | 79 | Synthetic | Stable | |
| 80Se | 34 | 46 | 80 | 49.61% | Stable | N/A |
| 81Se | 34 | 47 | 81 | Synthetic | ||
| 82Se | 34 | 48 | 82 | 8.73% | Stable | N/A |
| 83Se | 34 | 49 | 83 | Synthetic | ||
| 84Se | 34 | 50 | 84 | Synthetic | ||
| 85Se | 34 | 51 | 85 | Synthetic | ||
| 86Se | 34 | 52 | 86 | Synthetic | ||
| 87Se | 34 | 53 | 87 | Synthetic | ||
| 88Se | 34 | 54 | 88 | Synthetic | ||
| 89Se | 34 | 55 | 89 | Synthetic | ||
| 90Se | 34 | 56 | 90 | Synthetic | ||
| 91Se | 34 | 57 | 91 | Synthetic | ||
| 92Se | 34 | 58 | 92 | Synthetic | ||
| 93Se | 34 | 59 | 93 | Synthetic | ||
| 94Se | 34 | 60 | 94 | Synthetic |
Regulatory and Health - Health and Safety Parameters and Guidelines
| DOT Hazard Class | {N/A, 6.1, N/A} |
| DOT Numbers | {N/A, 2658, N/A} |
| EU Number | - |
| NFPA Fire Rating | {N/A, 0, N/A} |
| NFPA Hazards | N/ A, N/ A, N/ A |
| NFPA Health Rating | {N/A, 2, N/A} |
| NFPA Reactivity Rating | {N/A, 0, N/A} |
| Autoignition Point | - |
| Flashpoint | - |
Database Search
List of unique identifiers to search the element in various chemical registry databases
| Database | Identifier number |
|---|---|
| CAS Number - Chemical Abstracts Service (CAS) | CAS7782-49-2 |
| RTECS Number | {N/A, RTECSVS7700000, N/A} |
| CID Number | {CID6326970, CID6326970, CID139346} |
| Gmelin Number | - |
| NSC Number | - |
Compare Selenium with other elements
Compare Selenium with all Group 16 elements
Compare Selenium with all Period 4 elements
Compare Selenium with all Other Nonmetal elements
FAQs
What is the electronic configuration of Selenium?
The electronic configuration of Selenium is 1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p4.
What is the abbreviated electronic configuration of Selenium?
The abbreviated electronic configuration of Selenium is [Ar] 3d10 4s2 4p4. To form abbreviated notation of electronic configuration, the completely filled subshells are replaced by the noble gas of the preceding period in square brackets.
What is the symbol of Selenium?
Symbol of Selenium is Se. Selenium is a chemical element with symbol Se and atomic number 34.
What is the position of Selenium in the Periodic Table?
Selenium is a chemical element with the symbol Se and atomic number 34. Selenium is the 34 element on the periodic table. It is located in group 16 and period 4 in the modern periodic table.
What is the atomic number of Selenium?
The atomic number of Selenium is 34.
What is the color of Selenium?
Selenium is of Gray color.
Who discovered Selenium?
The element Selenium was discovered by J. Berzelius and G. Gahn in year 1817 in Sweden. Selenium was first isolated by J. Berzelius and G. Gahn in 1817.
How many valence electrons does a Selenium atom have?
Selenium has 6 valence electrons. Selenium has 34 electrons out of which 6 valence electrons are present in the 4s2 4p4 outer orbitals of atom.
What is the melting Point of Selenium?
Melting Point of Selenium is 494 K.
What is the boiling Point of Selenium?
Boiling Point of Selenium is 958 K.
What is the melting Point of Selenium in Kelvin?
Melting Point of Selenium in Kelvin is 494 K.
What is the boiling Point of Selenium in Kelvin?
Boiling Point of Selenium in Kelvin is 958 K.
What is the electronic configuration of Selenium 34?
The electronic configuration of Selenium will be 1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p4.
How do you write the electron configuration for Selenium?
The electronic configuration of Selenium will be 1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p4.