The electronegativity of sodium is 0.9, while the electronegativity of bromine is 2.8. This means that bromine has a greater tendency to attract electrons in a chemical bond than sodium does.
The difference in electronegativity between sodium and bromine is 1.9 (2.8 - 0.9). This difference is considered to be large, and it results in the formation of a polar covalent bond between sodium and bromine. In a polar covalent bond, the electrons are shared unequally between the two atoms, with the more electronegative atom having a greater share of the electrons.
The difference in electronegativity between sodium and bromine also affects the physical properties of the two elements. Sodium is a soft, silvery metal that is highly reactive, while bromine is a brown, nonmetallic liquid that is toxic and corrosive. The difference in electronegativity between the two elements results in different bonding properties, which in turn lead to different physical properties.
