Question

Describe the trend of electron affinity along a period.

Short answer

Answer: As we move from left to right across a period, electron affinity generally increases (becomes more positive) due to an increase in the effective nuclear charge and a decrease in atomic size, while electron shielding remains approximately constant. Factors that influence electron affinity include the effective nuclear charge, atomic size, and electron shielding.

Step-by-step solution

Understand Electron Affinity

Electron affinity is the energy change that occurs when an electron is added to a neutral atom in the gas phase. A more positive electron affinity value indicates that the atom is more likely to gain an electron, while a more negative value signifies that the atom is less likely to gain an electron. Factors that influence electron affinity include the effective nuclear charge, atomic size, and electron shielding.

Analyze the factors affecting electron affinity

Along a period in the periodic table, three factors influence the trend of electron affinity: 1. Effective nuclear charge: It is the net charge experienced by the outermost (valence) electrons in an atom. It increases across a period from left to right because the number of protons increases, leading to a stronger attraction of the nucleus for the electrons. 2. Atomic size: The size of the atom decreases across a period from left to right due to the increasing effective nuclear charge. A smaller atomic size means that the added electron will be closer to the nucleus and experience a strong attraction, which increases the electron affinity. 3. Electron shielding: It is the reduction in the effective nuclear charge experienced by an electron due to the presence of other electrons in the inner shells. As we move across a period, electron shielding remains relatively constant since electrons are being added to the same energy level.

Describe the general trend

As we move from left to right across a period, electron affinity generally increases (becomes more positive) due to an increase in the effective nuclear charge and a decrease in atomic size, while electron shielding remains approximately constant. In general, nonmetals have higher electron affinities than metals, as nonmetals are more likely to accept electrons to achieve a stable electron configuration. However, there are a few exceptions to the trend, like noble gases, which have stable electron configurations and possess a very low electron affinity.