In physics and chemistry, ionization energy (American English spelling) or ionisation energy (British English spelling), denoted Ei is the base measure of energy required to expel the most inexactly bound electron, the valence electron, of a disengaged impartial vaporous particle or atom. It is quantitatively communicated as
X + energy → X+ + e−
Where X is any atom or molecule capable of ionization, X+ is that atom or molecule with an electron removed, and e− is the removed electron. This is generally an endothermic process. Generally, the closer the outermost electrons are to the nucleus of the atom , the higher the atom’s or element’s ionization energy.
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What is Ionization Energy? Definition, Concept, and Example
The sciences of material science and science utilize distinctive proportions of ionization energy. In material science, the unit is the measure of energy required to expel a solitary electron from a solitary iota or atom, communicated as electron volts. In science, the unit is the measure of energy required for the majority of the iotas in a mole of substance to lose one electron every: molar ionization energy or enthalpy, communicated as kilojoules per mole (kJ/mol) or kilocalories per mole (kcal/mol).
Correlation of Ei of components in the occasional table uncovers two intermittent patterns:
- Ei generally increases as one moves from left to right within a given period (that is, row).
- Ei generally decreases as one moves from top to bottom in a given group (that is, column).
The last pattern results from the external electron shell being logically more distant from the core, with the expansion of one inward shell for every line as one moves down the section.
The nth ionization energy alludes to the measure of energy required to expel an electron from the species with a charge of (n-1). For instance, the initial three ionization energies are characterized as pursues:
- 1st ionization energy: X → X+ + e−
- 2nd ionization energy: X+ → X2+ + e−
- 3rd ionization energy: X2+ → X3+ + e−
The term ionization potential is a more seasoned name for ionization energy, on the grounds that the most established technique for estimating ionization energy depended on ionizing an example and quickening the electron expelled utilizing an electrostatic potential.
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Concept of Ionization Energy
The Ionization Energy (eV) is the energy required to take the electron from n = 1 (ground state or most stable state) to infinity. Hence taking 0 (eV) reference at infinity, the Ionization Energy can be written as:
The concept of Ionization Energy supports the evidence of Bohr model of atom that the electron can revolve around the nucleus in a fixed or discrete energy levels or shells represented by the principal quantum number ‘n’.
As the first electron goes away from the vicinity of the positive nucleus, then greater energy is required to remove the next loosely bound electron as the electrostatic force of attraction increases, i.e., the second Ionization Energy is greater than the first one.
See Also: Potential Difference Definition
Ionization Energy Example
For example, the first ionization energy of Sodium (Na) is given as:
And its second Ionization Energy is
Hence, IE2 > IE1 (eV). This is also true if there are K number of ionizations, then IE1 < IE2 < IE3……….< IEk
Metals have low Ionization Energy. Low Ionization Energy implies better conductivity of the element.
For example, the conductivity of Silver (Ag, atomic number Z = 47) is 6.30 × 107 s/m and its Ionization Energy is 7.575 eV and for Copper (Cu, Z = 29) is 5.76 × 107 s/m and its Ionization Energy is 7.726 eV. In conductors the low Ionization Energy causes the electrons to move throughout the positively charged lattice, forming an electron cloud.
Factors Affecting Ionization Energy
In the periodic table, the general trend is that the Ionization Energy increases from left to right and decreases from top to bottom. So the factors affecting ionization energy can be summarised below:
- Size of the Atom: The Ionization Energy decreases with the size of the atom because as the atomic radius increases the columbic force of attraction between the nucleus and outermost electron decreases and vice-versa.
- Shielding Effect: The presence of inner shell electrons shield or weaken the columbic force of attraction between the nucleus and the valence shell electrons. Hence ionization energy decreases. The number of inner electrons means more shielding. However, in the case of gold, the Ionization Energy is greater than silver even if the size of gold is more than silver. This is due to the weak shielding offered by the inner d and f orbitals in case of gold.
- Nuclear Charge: The more the nuclear charge, the more it will be difficult to ionize the atom due to more attraction force between nucleus and electrons.
- Electronic Configuration: The more stable the electronic configuration of the atom, the more difficult is to withdraw an electron hence more Ionization Energy.
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Ionization Energy Definition, Concept, and Example
After going through the above concept of Ionization Energy we can now establish a Ionization Energy definition. I hope you enjoy when reading this article, thank you.