Across a period electron affinity decreasesQuestion 18Answera.Falseb.True

The statement "Across a period electron affinity decreases" is generally false.

Electron affinity is the energy change that occurs when an electron is added to a neutral atom to form a negative ion. In general, as you move from left to right across a period (horizontal row) on the periodic table, electron affinity increases.

This is because as you move across a period, the number of protons in the nucleus increases, which increases the positive charge of the nucleus and its ability to attract electrons. At the same time, the added electrons go into the same energy level, so they are approximately the same distance from the nucleus and there is not a significant increase in electron-electron repulsion to counteract the increased nuclear charge.

There are some exceptions to this trend (for example, noble gases have very low electron affinities because their electron shells are full), but in general, electron affinity increases across a period.

So, the correct answer is a. False.