Question

what is electronegativity of elements? give reason with Na,C and B.

Answer 1

Electronegativity is the tendency of an atom to attract the bonded pair of electrons towards itself. More is the electronegativity, more strongly an atom attracts electrons.
Sodium is a metal and has a tendency to donate electrons. So, it is not electronegative but electropositive instead.
Carbon is a non-metal and has a tendency to attract electrons. Therefore, it is a electronegative element.
Boron is a non-metal but is less electronegative as compared to other non-metals.