Which statement is true about electronegativity?

A. The size of an atom and the number of valence electrons determine an atom's electronegativity.

B. Electronegativity increases as the number of protons in an atom decreases.

C. Electronegativity is the ability of an atom to attract electrons.

D. A very electronegative atom gives up electrons quickly in reactions

Electronegativity is a measure of the ability of an atom to attract electrons. The value tends to increase on moving from left to right across a period in the periodic table. This is because as the atomic number increases so does the nuclear charge which causes the added electron to experience a stronger nuclear attraction.

For example, if the consider the second period, then Lithium which is present in the extreme left will show a greater tendency to lose electrons (lower electronegativity) while Fluorine present in the extreme right will show a greater tendency to attract electrons and therefore high electronegativity. Thus, when Li and F combine, they form what is called an ionic bond.

Ans C) True statement

Electronegativity generally increases from left to right across a period.