HS Chemistry - Essentials

Electronegativity & Ionization Energy

Overview of The Page

This page will cover:

• What is electronegativity?
• What is ionization energy?

Electronegativity is the tendency of an atoms to attract electrons to itself. Atoms with a higher electronegativity pull more strongly on their electrons, and atoms with a lower electronegativity pull less strongly on their electrons.

The protons in a nucleus exert a collective force on all the electrons in the atom. However, due to electron shielding $covered more [on the next page](8-Electron-Repulsion-and-Shielding.md)$, the valence electrons only experience an attractive force equivalent to the number of valence electrons. This force is shared among them. The more valence electrons that there are, the stronger this force, and the closer each electron is pulled to the nucleus. This allows it to exert a stronger pull on other electrons not part of the atom. In other words, the more valence electrons that the atom has, the more the atom can attract electrons to itself, and the higher its electronegativity.

This leads to the trend of non-metals having higher electronegativities than metals, as non-metals have more valence electrons.

The number of shells also influences the electronegativity of the atom. If an atom is exerting a force of +2 on its valence electrons, the electrons will feel a stronger pull if they are on the second electron shell than if they are on the sixth electron shell, as they are closer to the source of the attractive force $the nucleus of the atom$. Therefore, the more shells an atom has, the lower its electronegativity.

Furthermore, since more shells means a greater atomic radius, and fewer valence electrons means a greater atomic radius, a greater atomic radius directly corresponds with lower electronegativity.

Noble gases do not have an electronegativity value, as they are unable to attract other atoms' electrons due to having a full valence shell. However, apart from that $and Hydrogen, as Hydrogen only has one electron shell$, the trend for electronegativity corresponds with the trend for atomic radius. Fluorine $colored red$ is the most electronegative element, and Francium $colored blue$ is the least electronegative element:

Ionization energy is the energy needed to remove an electron from an atom $the first ionization energy is the amount of energy needed to remove one electron, the second ionization energy is the amount of energy needed to remove two electrons, etc.$.

As a more electronegative element holds onto its valence electrons more tightly, it has a higher ionization energy than a less electronegative element in the same period. However, an element with fewer valence shells will typically have a higher ionization energy, as the nucleus is able to more tightly hold onto electrons that are closer.