Final answer:
The difference in basicity and nucleophilicity depends on the atoms being compared. Hydride ion (H¯) is a stronger base but a poor nucleophile, while elements like SH¯, Cl¯, Br¯, and I¯ are weak bases but good nucleophiles.
Step-by-step explanation:
The difference in basicity and nucleophilicity depends on the atoms being compared. In general, the hydride ion (H¯) from the 1st row is a stronger base but a poor nucleophile. On the other hand, elements from the 3rd row and higher, such as SH¯, Cl¯, Br¯, and I¯, are weak bases but good nucleophiles. Nucleophilicity is also affected by steric factors and solvents. Base strength is described as stronger or weak, and nucleophilic strength is described as good or poor.