Organic Chemistry MCAT Practice Exam

What trend describes nucleophilicity in the periodic table?

1. Increases from top right to bottom left

2. Increases from bottom right to top left

3. Increases across a period

4. Decreases down a group

The correct answer is: Increases from top right to bottom left

Nucleophilicity is influenced by several factors, including charge, electronegativity, and the size of the nucleophile. In the context of the periodic table, nucleophilicity generally increases from the top right to the bottom left. This trend aligns with the behavior of atoms and molecules as they interact during nucleophilic substitution reactions. As you move from the top right to the bottom left of the periodic table, the elements tend to become larger, which often leads to increased nucleophilicity due to the greater availability of their valence electrons. Larger atoms have more diffuse electron clouds, making it easier for them to donate electrons. Additionally, the decrease in electronegativity when moving towards the left means that atoms become less likely to hold onto their electrons tightly, further enhancing their nucleophilic character. In contrast, when considering the options that suggest other trends, the idea that nucleophilicity increases across a period does not hold, as this would imply that elements on the right side would be better nucleophiles, which is not accurate. Similarly, the decrease down a group does not reflect nucleophilicity accurately; while sterics play a role, nucleophilicity can actually increase with larger, more polarizable