What are the period and group trends in electronegativities

Electronegativity of an element decreases as we move down a group on the periodic table and electronegativity increases while moving from left to right across a period on the periodic table.

Explanation:

The electronegativity increases as we move from left to right across a period because from left to right across a period, the nuclear charge is increasing Hence the attraction for the valence electrons also increases. As we move down a group, the atoms of each element have an increasing number of energy levels. The distance between the nucleus and valence electron shell increases and reduces the attraction for valence electrons. Hence electronegativity decreases as we move from top to bottom down a group.