What defines the ability of an atom to attract electrons in a covalent bond?

The ability of an atom to attract electrons in a covalent bond is defined by electronegativity. Electronegativity is a measure of an atom's tendency to pull electrons towards itself when participating in a chemical bond. It is key in determining how evenly or unevenly the electrons are distributed between two bonded atoms.

Atoms with high electronegativity, such as fluorine or oxygen, have a strong ability to attract shared electrons, resulting in a polar covalent bond if combined with a less electronegative atom. Conversely, atoms with low electronegativity, such as sodium or potassium, will attract shared electrons less effectively.

Other options, while related to the behavior of electrons in atoms, do not define this specific ability in the context of covalent bonding. Electron affinity measures the energy change when an electron is added to a neutral atom, indicating its tendency to gain electrons rather than attract in bonding. Ionization energy refers to the energy required to remove an electron from an atom, reflecting its tendency to lose electrons, not attract them. Atomic radius is about the size of an atom; larger atoms tend to have lower electronegativity because their outer electrons are further from the nucleus and thus less attracted to it.

Thus,