- Electronegativity is the ability of an atom to attract a pair of electrons towards itself in a covalent bond
- This phenomenon arises from the positive nucleus’s ability to attract the negatively charged electrons, in the outer shells, towards itself
- The Pauling scale is used to assign a value of electronegativity for each atom
- Fluorine is the most electronegative atom on the Periodic Table, with a value of 4.0 on the Pauling Scale
- It is best at attracting electron density towards itself when covalently bonded to another atom
- Attraction exists between the positively charged protons in the nucleus and negatively charged electrons found in the energy levels of an atom
- An increase in the number of protons leads to an increase in nuclear attraction for the electrons in the outer shells
- Therefore, an increased nuclear charge results in an increased electronegativity
- The atomic radius is the distance between the nucleus and electrons in the outermost shell
- Electrons closer to the nucleus are more strongly attracted towards its positive nucleus
- Those electrons further away from the nucleus are less strongly attracted towards the nucleus
- Therefore, an increased atomic radius results in a decreased electronegativity
As the atomic radius increases, the nucleus has less of an attraction for the bonding electrons causing atom A to have a higher electronegativity than atom B
- Filled energy levels can shield (mask) the effect of the nuclear charge causing the outer electrons to be less attracted to the nucleus
- Therefore, the addition of extra shells and subshells in an atom will cause the outer electrons to experience less of the attractive force of the nucleus
- Sodium (Period 3, Group 1) has higher electronegativity than caesium (Period 6, Group 1) as it has fewer shells and therefore the outer electrons experience less shielding than in caesium
- Thus, an increased number of inner shells and subshells will result in a decreased electronegativity
The nuclear charge, atomic radius and shielding are all linked to each other.
As nuclear charge increases, the nucleus has a greater attractive force on the electrons in shells given that the shielding doesn’t increase.
As a result of this, the atomic radius decreases.