Which of the following pairs is correctly matched with regard to periodic trends?

The choice indicating that electronegativity increases from left to right across a period on the periodic table is indeed correct. Electronegativity, which refers to the tendency of an atom to attract electrons in a bond, generally increases as you move from left to right. This increase is primarily due to the higher effective nuclear charge experienced by the electrons in the same valence shell as you move across a period, as additional protons in the nucleus attract the bonding electrons more strongly.

As for the other options, atomic radius does not decrease from top to bottom; instead, it generally increases as you move down a group due to the addition of electron shells, which outweighs the increasing nuclear charge. Similarly, ionization energy tends to decrease from top to bottom within a group because the outer electrons are further from the nucleus and less tightly bound, making them easier to remove. Finally, atomic radius decreases from left to right, not increases, as the effective nuclear charge increases, pulling the electrons closer to the nucleus. This trend in atomic radius is contrary to what is suggested in the incorrect option for atomic radius.