Question

elements are organized on the periodic table based on their properties. which statement correctly predicts and explains the chemical reactivity of two different metals?
barium (ba) is less reactive than calcium (ca) because the valence electrons in calcium atoms are farther from the nuclei and harder to remove.
strontium (sr) is more reactive than magnesium (mg) because the valence electrons in strontium atoms are farther from the nuclei and harder to remove.
rubidium (rb) is more reactive than sodium (na) because the valence electrons in sodium atoms are closer to the nuclei and easier to remove.
lithium (li) is less reactive than potassium (k) because the valence electrons in lithium atoms are closer to the nuclei and harder to remove.

Explanation:

To solve this, we analyze each option using the concept of metal reactivity (related to ease of removing valence electrons) and periodic table trends (atomic size, distance of valence electrons from nucleus, and effective nuclear charge):

1. Option 1 (Barium vs. Calcium): Barium (Ba) is below Calcium (Ca) in Group 2. Atomic size increases down a group, so Ba’s valence electrons are farther from the nucleus (easier to remove). Thus, Ba should be more reactive than Ca. The statement says Ba is less reactive (incorrect) and claims Ca’s electrons are farther (false, since Ca is above Ba).

1. Option 2 (Strontium vs. Magnesium): Strontium (Sr) is below Magnesium (Mg) in Group 2. Sr’s valence electrons are farther from the nucleus (easier to remove), so Sr is more reactive. But the statement claims Sr’s electrons are “harder to remove” (contradicts reactivity logic—easier removal means more reactive). Thus, incorrect.

1. Option 3 (Rubidium vs. Sodium): Rubidium (Rb) is below Sodium (Na) in Group 1. Rb’s valence electrons are farther from the nucleus (easier to remove), so Rb is more reactive. The statement claims Na’s electrons are “easier to remove” (false, since Rb is more reactive). Thus, incorrect.

1. Option 4 (Lithium vs. Potassium): Lithium (Li) is above Potassium (K) in Group 1. Li’s valence electrons are closer to the nucleus (harder to remove), so Li is less reactive than K (which has electrons farther from the nucleus, easier to remove). This matches the statement’s claim.

Answer:

Lithium (Li) is less reactive than potassium (K) because the valence electrons in lithium atoms are closer to the nuclei and harder to remove.