Arrange the metals Potassium, Lithium, Sodium in order of increasing reactivity.

Arrange the metals Potassium, Lithium, Sodium in order of increasing reactivity.

• A. Potassium, Lithium, Sodium
• B. Lithium, Sodium, Potassium
• C. Sodium, Potassium, Lithium
• D. Lithium, Potassium, Sodium

Answer: (B)

The main idea here is how reactivity changes for alkali metals as you move down the group. As you go from lithium to sodium to potassium, the outer electron is farther from the nucleus and more shielded by inner electrons, so it’s easier to remove. That means reactivity increases down the group. So the order from least to most reactive is lithium, then sodium, then potassium. This trend matches how their reactions with water become progressively more vigorous (lithium reacts slowly, sodium faster, potassium most vigorously).

The main idea here is how reactivity changes for alkali metals as you move down the group. As you go from lithium to sodium to potassium, the outer electron is farther from the nucleus and more shielded by inner electrons, so it’s easier to remove. That means reactivity increases down the group. So the order from least to most reactive is lithium, then sodium, then potassium. This trend matches how their reactions with water become progressively more vigorous (lithium reacts slowly, sodium faster, potassium most vigorously).