Let's evaluate each statement based on the periodic trends of reactivity among metals.
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Barium (Ba) is less reactive than calcium (Ca) because the valence electrons in calcium atoms are farther from the nuclei and harder to remove.
- This statement is incorrect. Barium is actually more reactive than calcium. As you move down the alkaline earth metals group (Group 2), reactivity increases because the valence electrons are further from the nucleus and are easier to remove due to increased shielding and atomic size.
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Strontium (Sr) is more reactive than magnesium (Mg) because the valence electrons in strontium atoms are farther from the nuclei and harder to remove.
- This statement is also incorrect. While it is true that strontium is more reactive than magnesium, it is because the valence electrons in strontium are farther from the nucleus and easier to remove, not harder.
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Rubidium (Rb) is more reactive than sodium (Na) because the valence electrons in sodium atoms are closer to the nuclei and easier to remove.
- This statement is incorrect. Rubidium is indeed more reactive than sodium, but the explanation is flawed. The reactivity of rubidium is due to its valence electrons being farther from the nucleus (not sodium's) and therefore easier to remove.
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Lithium (Li) is less reactive than potassium (K) because the valence electrons in lithium atoms are closer to the nuclei and harder to remove.
- This statement is correct. Lithium is less reactive than potassium because potassium has its valence electron further away from the nucleus, making it easier to remove compared to lithium.
The most accurate statement that correctly predicts and explains the chemical reactivity based on periodic trends is:
4. Lithium (Li) is less reactive than potassium (K) because the valence electrons in lithium atoms are closer to the nuclei and harder to remove.
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