Difference Between Electronegativity and Ionization Energy

Electronegativity vs Ionization Energy

Atoms are the small building blocks of all existing substances. They are so tiny that we cannot even observe with our naked eye. Atom is made up of a nucleus, which has protons and neutrons. Other than neutrons and positrons, there are other small sub atomic particles in the nucleus, and there are electrons circling around the nucleus in orbitals. Because of the presence of protons, atomic nuclei are positively charged. The electrons in the outer sphere are negatively charged. Hence, the attractive forces between the positive and negative charges of the atom maintain the structure.

Ionization Energy

Ionization energy is the energy that should be given to a neutral atom to remove an electron from it. The removal of electron means to remove it an infinite distance from the species so that there are no attraction forces between the electron and the nucleus. Ionization energies are named as first ionization energy, second ionization energy and so on depending on the number of electrons removing out. This will give rise to cations with +1, +2, +3 charges and so on. In small atoms, the atomic radius is small. Therefore, the electrostatic attraction forces between the electron and the neutron is much higher compared to an atom with lager atomic radius. This increases the ionization energy of a small atom. When the electron is located closer to the nucleus, the ionization energy will be higher. Thus, the (n+1) ionization energy is always higher than the nth ionization energy. Also when comparing two 1st ionization energies of different atoms, they also vary. For example, first ionization energy of sodium (496 kJ/mol) is much lower than the first ionization energy of chlorine (1256 kJ/mol). 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.


Electronegativity is the tendency of an atom to attract the electrons in a bond towards it. Simply, this shows the “likeness” of an atom towards the electrons. Pauling scale is commonly used 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 the value of 4.0 in the Pauling scale. Group one and two elements have a 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. 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 result. If the electronegativity difference between the two is high, then a ionic bond will result.


What is the difference between Electronegativity and Ionization Energy?

• Electronegativity is the tendency of an atom to attract the electrons in a bond towards it.

•  Ionization energy is the energy that should be given to a neutral atom to remove an electron from it.