Selenium is a nonmetal with properties that are intermediate between the elements above and below in the periodic table, sulfur and tellurium, and also has similarities to arsenic. It rarely occurs in its elemental state or as pure ore compounds in the Earth’s crust.
Electron Affinity – Selenium
Electron affinity of Selenium is 195 kJ/mol.
In chemistry and atomic physics, the electron affinity of an atom or molecule is defined as:
the change in energy (in kJ/mole) of a neutral atom or molecule (in the gaseous phase) when an electron is added to the atom to form a negative ion.
X + e– → X– + energy Affinity = – ∆H
In other words, it can be expressed as the neutral atom’s likelihood of gaining an electron. Note that, ionization energies measure the tendency of a neutral atom to resist the loss of electrons. Electron affinities are more difficult to measure than ionization energies.
Electronegativity of Selenium
Electronegativity of Selenium is 2.55.
Electronegativity, symbol χ, is a chemical property that describes the tendency of an atom to attract electrons towards this atom. For this purposes, a dimensionless quantity the Pauling scale, symbol χ, is the most commonly used.
The electronegativity of Selenium is: χ = 2.55
First Ionization Energy of Selenium
First Ionization Energy of Selenium is 9.7524 eV.
Ionization energy, also called ionization potential, is the energy necessary to remove an electron from the neutral atom.
X + energy → X+ + e−
where X is any atom or molecule capable of being ionized, X+ is that atom or molecule with an electron removed (positive ion), and e− is the removed electron.
A Selenium atom, for example, requires the following ionization energy to remove the outermost electron.
Se + IE → Se+ + e− IE = 9.7524 eV
Electrons and Electron Configuration
The number of electrons in an electrically-neutral atom is the same as the number of protons in the nucleus. Therefore, the number of electrons in neutral atom of Selenium is 34. Each electron is influenced by the electric fields produced by the positive nuclear charge and the other (Z – 1) negative electrons in the atom.
Since the number of electrons and their arrangement are responsible for the chemical behavior of atoms, the atomic number identifies the various chemical elements. The configuration of these electrons follows from the principles of quantum mechanics. The number of electrons in each element’s electron shells, particularly the outermost valence shell, is the primary factor in determining its chemical bonding behavior. In the periodic table, the elements are listed in order of increasing atomic number Z.
Electron configuration of Selenium is [Ar] 3d10 4s2 4p4.
Possible oxidation states are +4,6/-2.
|Number of electrons||34|
|Electron configuration||[Ar] 3d10 4s2 4p4|
|Electron affinity [kJ/mol]||195|
|Electronegativity [Pauling scale]||2.55|
|First ionization energy [eV]||9.7524|
Properties of other elements