Electronegativity is a measure of the attraction an atom has for electrons when it is involved in a chemical bond.
Noble gases have no electronegativity because they generally do not bond.
Elements that have high ionization energy and high electron affinity will also have high electronegativity since their nuclei strongly attract electrons. Electronegativity increases from left to right as we move across a period and decreases as we move down any group or family.
Electronegativity Differences between atoms can be used to determine the type of bonding that occurs.
If the difference between 2 atoms is small (less than 1.7) the bond is covalent.
If the difference is large (greater than 1.7) the bond is considered ionic.
Exceptions- HF is covalent not ionic (difference of 1.9)
BF3 is covalent (difference of 2.0)
BeF2 is covalent (difference of 2.5)
on to Types of Bonds