What trend is observed in atomic radii while moving from left to right across the periodic table's second row?

The trend in atomic radii while moving from left to right across the periodic table's second row is indeed a uniform decrease. This is primarily due to the increasing positive charge in the nucleus as more protons are added while the electrons are filling the same principal energy level. The increased nuclear charge results in a stronger attraction between the nucleus and the electrons. As a result, the electrons are pulled closer to the nucleus, leading to a decrease in atomic radius.

As you move across the second row, elements begin with lithium on the left and end with neon on the right. For each element, as protons are added, the effective nuclear charge increases. Because the number of electron shells does not change, the balance of the electron-electron repulsion and the nuclear attraction shifts, causing the overall size of the atom to decrease consistently through this row of the periodic table.