The key difference between electronegativity and ionization energy is that electronegativity explains the attraction of electrons while ionization energy refers to the removal of electrons from an atom.
Atoms are the building blocks of all existing substances. They are so tiny that we cannot even observe them with our naked eye. An atom consists of a nucleus, which has protons and neutrons. In addition to neutrons and positrons, there are other small subatomic particles in the nucleus, and there are electrons circling around the nucleus in orbitals. Because of the presence of protons, atomic nuclei have a positive charge. The electrons in the outer sphere have a negative charge. Hence, the attractive forces between the positive and negative charges of the atom maintain its structure.
CONTENTS
1. Overview and Key Difference
2. What is Electronegativity
3. What is Ionization Energy
4. Side by Side Comparison –Electronegativity vs Ionization Energy in Tabular Form
5. Summary
What is Electronegativity?
Electronegativity is the tendency of an atom to attract the electrons in a bond towards it. In other words, this shows the attraction of an atom towards the electrons. We commonly use the Pauling scale to indicate the electronegativity of elements.
In the periodic table, electronegativity changes according to a pattern. From left to right on a period, electronegativity increases, and from top to bottom on a group, electronegativity decreases. Therefore, fluorine is the most electronegative element with a value of 4.0 on the Pauling scale. Group one and two elements have less electronegativity; thus, they tend to form positive ions by giving electrons. Since group 5, 6, 7 elements have a higher electronegativity value, they like to take electrons in and from negative ions.
Figure 01: Electronegativity According to the Pauling Scale
Electronegativity is also important in determining the nature of bonds. If the two atoms in the bond have no electronegativity difference, then a pure covalent bond will form. Moreover, if the electronegativity difference between the two is high, then an ionic bond will be the result. If there is a slight difference, a polar covalent bond will form.
What is Ionization Energy?
Ionization energy is the energy that should be given to a neutral atom to remove an electron from it. The removal of an electron means to remove it an infinite distance from the species so that there are no attraction forces between the electron and the nucleus (complete removal).
We can name ionization energies as first ionization energy, second ionization energy and so on, depending on the number of electrons removed from the atom. At the same time, this will give rise to cations with +1, +2, +3 charges, and so on.
Figure 1: Ionization Energy Trends for the First Ionization in Each Period of the Periodic Table
In small atoms, the atomic radius is small. Therefore, the electrostatic attraction forces between the electron and the neutron are much higher compared to an atom with a larger atomic radius. It increases the ionization energy of a small atom. If the electron is closer to the nucleus, the ionization energy will be higher.
Moreover, the first ionization energies of different atoms also vary. For example, the first ionization energy of sodium (496 kJ/mol) is much lower than the first ionization energy of chlorine (1256 kJ/mol). It is because by removing one electron, sodium can gain the noble gas configuration; hence, it readily removes the electron. In addition, the atomic distance is less in sodium than in chlorine, which lowers the ionization energy. Therefore, ionization energy increases from left to right in a row and bottom to top in a column of the periodic table (this is the inverse of atomic size increase in the periodic table). When removing electrons, there are some instances where the atoms gain stable electron configurations. At this point, ionization energies tend to jump into a higher value.
Difference Between Electronegativity and Ionization Energy?
Electronegativity is the tendency of an atom to attract the electrons in a bond towards it while ionization energy is the energy a neutral atom needs to remove an electron from it. Therefore, the key difference between electronegativity and ionization energy is that electronegativity explains the attraction of electrons while ionization energy refers to the removal of electrons from an atom.
Moreover, there is another significant difference between electronegativity and ionization energy based on their trends in the periodic table of elements. Electronegativity increases from left to right on a period and decreases top to bottom on a group. Whereas, ionization energy increases from left to right in a row and bottom to top in a column of the periodic table. However, sometimes, the atoms gain stable electron configurations, and thus, ionization energies tend to jump into a higher value.
Summary – Electronegativity vs Ionization Energy
The terms electronegativity and ionization energy explain the interactions between atomic nuclei and electrons. The key difference between electronegativity and ionization energy is that electronegativity explains the attraction of electrons while ionization energy refers to the removal of electrons from an atom.
Reference:
1. Helmenstine, Anne Marie. “Electronegativity Definition and Examples.” ThoughtCo, Oct. 17, 2018, Available here.
2. Helmenstine, Anne Marie. “Ionization Energy Definition and Trend.” ThoughtCo, Jan. 24, 2019, Available here.
Image Courtesy:
1. “Taula periòdica electronegativitat” By Joanjoc at Catalan Wikipedia – Transferred from ca.wikipedia to Commons (Public Domain) via Commons Wikimedia
2. “First Ionization Energy” By Sponk (PNG file)Glrx (SVG file)Wylve (zh-Hans, zh-Hant)Palosirkka (fi)Michel Djerzinski (vi)TFerenczy (cz)Obsuser (sr-EC, sr-EL, hr, bs, sh)DePiep (elements 104–108)Bob Saint Clar (fr)Shizhao (zh-Hans)Wiki LIC (es)Agung karjono (id)Szaszicska (hu) – Own work based on: Erste Ionisierungsenergie PSE color coded.png by Sponk (CC BY 3.0) via Commons Wikimedia