Se Selenium Element Information: Facts, Properties, Trends, Uses and comparison

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.

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
Classification	other nonmetal
Group in Periodic Table	16
Group Name	oxygen family
Period in Periodic Table	4
Block in Periodic Table	p-block
Electronic Configuration	[Ar] 3d10 4s2 4p4
Melting Point	221 °C
Boiling Point	685 °C
Electronic Shell Structure	[2, 8, 18, 6]
CAS Number	CAS7782-49-2

Neighborhood

Lanthanides

Actinide

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.

Atomic & Orbital Properties

Chemical Properties

Isotopes

Health and Safety Parameters and Guidelines

Databases

Compare Selenium with other elements

Selenium History

The element Selenium was discovered by Jöns Jakob Berzelius in year 1817 in Sweden . Selenium derived its name from the Greek selene, meaning 'moon'

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 %)
Abundance in Universe	3×10-6%
Abundance in Sun	N/A
Abundance in Meteorites	1.3e-05
Abundance in Earth's Crust	5×10-6%
Abundance in Oceans	4.5×10-8%
Abundance in Humans	5×10-6%

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	908.3	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 ( x_i, y_i, z_i) 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

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
Oxidation State	-2;-1 1;2;3;4;5;6
Atomic Term Symbol (Quantum Numbers)	³P₂

Shell Structure of Selenium - Electrons per energy level

34 Se Selenium - Electron Shell Structure | SchoolMyKids

n		s	p	d
1	K	2
2	L	2	6
3	M	2	6	10
4	N	2	4

Ground State Electronic Configuration of Selenium - neutral Selenium atom

The ground state 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 3d10 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

Atomic Structure of Selenium

Selenium atomic radius is 103 pm, while it's covalent radius is 116 pm.

Atomic Radius	103 pm (1.03 Å)
Atomic Volume	16.3851421457 cm³
Covalent Radius	116 pm (1.16 Å)
Van der Waals Radius	190 pm
Neutron Cross Section	11.7 σa/barns

Atomic Spectrum of Selenium

Atomic Spectrum of Selenium | SchoolMyKids

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
1	941
2	2045
3	2973.7
4	4144
5	6590
6	7880
7	14990

Selenium Physical Properties

Refer to below table for Selenium Physical Properties

Density	4.819 g/cm3
Molar Volume	16.3851421457 cm3

Elastic Properties

Young Modulus	10 GPa
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	N/A
Brinell Hardness	736 MPa

Selenium Electrical Properties

Selenium is N/A of electricity. Refer to table below for the Electrical properties of Selenium

Electrical Conductivity	N/A
Resistivity	N/A
Superconducting Point	N/A

Selenium Heat and Conduction Properties

Thermal Conductivity	0.52 W/(m K)
Thermal Expansion	N/A

Selenium Magnetic Properties

Magnetic Type	Diamagnetic
Curie Point	N/A
Mass Magnetic Susceptibility	-4×10-9
Molar Magnetic Susceptibility	-3.16×10-10
Volume Magnetic Susceptibility	-1.93e-05

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 (221 °C)
Boiling Point	958 K (685 °C)
Critical Temperature	1766 K
Superconducting Point	N/A

Enthalpies of Selenium

Heat of Fusion	5.4 kJ/mol
Heat of Vaporization	26 kJ/mol
Heat of Combustion	{"N/A", "N/A", "N/A"} J/(kg K)

Selenium Isotopes - Nuclear Properties of Selenium

Isotopes of rhodium. Naturally occurring Selenium has 5 stable isotope - 74Se, 76Se, 77Se, 78Se, 80Se.

Isotope	% Abundance	T half	Decay Mode
65Se
66Se
67Se
68Se
69Se
70Se
71Se
72Se
73Se
74Se	0.89%	Stable	N/A
75Se
76Se	9.37%	Stable	N/A
77Se	7.63%	Stable	N/A
78Se	23.77%	Stable	N/A
79Se
80Se	49.61%	Stable	N/A
81Se
82Se	8.73%
83Se
84Se
85Se
86Se
87Se
88Se
89Se
90Se
91Se
92Se
93Se
94Se

Regulatory and Health - Health and Safety Parameters and Guidelines

CAS Number	CAS7782-49-2
RTECS Number	{N/A, RTECSVS7700000, N/A}
DOT Hazard Class	{N/A, 6.1, N/A}
DOT Numbers	"N/A", {2658}, "N/A"
EU Number	{N/A, N/A, N/A}
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	N/A
Flashpoint	N/A

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
CID Number	{CID6326970, CID6326970, CID139346}
Gmelin Number	{N/A, N/A, N/A}
NSC Number	{N/A, N/A, N/A}
RTECS Number	{N/A, RTECSVS7700000, N/A}