Which trend typically decreases as you move from left to right on the periodic table?

As you move from left to right across the periodic table, the atomic radius typically decreases. This trend is primarily due to the increasing positive charge of the nucleus as protons are added to the atomic number. This increase in nuclear charge pulls the electrons closer to the nucleus, reducing the size of the electron cloud and, therefore, the atomic radius.

Additionally, as electrons are added to the same energy level across a period, there is not a significant increase in electron shielding that would offset the increasing nuclear charge. As a result, the overall effective nuclear charge that the outermost electrons experience grows, leading to a tighter hold on these electrons and a smaller atomic size.

In contrast, electronegativity and ionization energy tend to increase as you move from left to right, while electron affinity can vary depending on the specific elements involved. Thus, the trend of decreasing atomic radius is the most consistent and widely observed as you progress across the periodic table.