Which of the following correctly describes the trend in metallic character across Period 3 of the periodic table from left to right?

Across a period from left to right, the nuclear charge increases while electrons are added to the same shell, making it progressively harder to lose electrons. This means elements become less metallic (and more non-metallic) across the period. In Period 3, Na and Mg are metals, Al is a metalloid/amphoteric metal, while Si, P, S, Cl, and Ar are non-metals.