what is electronegativity and explain the trend in electronegativity as we go down the group?

Electronegativity is the power of an atom to attract electrons in a covalent bond towards itself. As we go down the group, electronegativity decreases because the atomic radii increases. The atomic radii increases because the number of electron shells increases. The nucleus is further away from the bonding pair of electrons and therefore it is less able to attract it.