Electronegativity & Bonding
- Electronegativity is the power of an atom to attract the pair of electrons in a covalent bond towards itself
- The electron distribution in a covalent bond between elements with different electronegativities will be unsymmetrical
- This phenomenon arises from the ability of the positive nucleus 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
First three rows of the periodic table showing electronegativity values
- 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 electrons towards itself when covalently bonded to another atom
Electron distribution in the C-F bond of fluoromethane
Ionic and covalent bonding
- Elements with large differences in electronegativity tend to form ionic bonds
- Atoms of elements with similar electronegativity tend to form covalent bonds
- Intermediate differences in electronegativity between covalently bonded atoms lead to polarity in the bond
- As a rule, an electronegativity difference of 2 or more on the Pauling scale between atoms leads to the formation of an ionic bond
- A difference of less than 2 between atoms leads to covalent bond formation