What is the trend of electronegativity across a period?

Electronegativity is defined as the tendency of an atom to attract a bonding pair of electrons. As you move across a period from left to right in the periodic table, the electronegativity of the elements generally increases. This is primarily due to the increase in nuclear charge, as protons are added to the nucleus while the number of electron shielding remains relatively constant.

As a result of this increased positive charge in the nucleus, the atoms can exert a stronger pull on the bonding electrons. The increased effective nuclear charge also leads to a greater attraction between the nucleus and the outer electrons, making it more likely for that atom to attract electrons from a bonding pair. Thus, elements on the right side of the periodic table, such as fluorine and oxygen, are more electronegative than elements on the left side, such as sodium and magnesium.

This trend is significant in predicting the behavior of elements in chemical reactions and their bonding characteristics.