What is a key reason for the high reactivity of alkali metals with water?

What is a key reason for the high reactivity of alkali metals with water?

• A. One electron in the outer shell
• B. Seven electrons in the outer shell
• C. Full outer shell
• D. Noble gases

Answer: (A)

Having one electron in the outer shell makes alkali metals highly reactive with water because they can easily lose that electron to form a stable, positively charged ion. This loss releases energy and drives the reaction with water, producing hydroxide ions and hydrogen gas. The single valence electron is held loosely due to low ionization energy, so it’s readily donated when the metal meets water. As you go down the group, the outer electron is further from the nucleus and more shielded, so removing it becomes even easier, explaining the increasing vigour of the reaction down the series. If the outer shell had seven electrons, the tendency would be to gain rather than lose electrons to reach a full octet, which would make the substance far less reactive with water. A full outer shell is characteristic of very unreactive, stable species. Noble gases have full outer shells and are largely inert, so they don’t react with water.

Having one electron in the outer shell makes alkali metals highly reactive with water because they can easily lose that electron to form a stable, positively charged ion. This loss releases energy and drives the reaction with water, producing hydroxide ions and hydrogen gas. The single valence electron is held loosely due to low ionization energy, so it’s readily donated when the metal meets water. As you go down the group, the outer electron is further from the nucleus and more shielded, so removing it becomes even easier, explaining the increasing vigour of the reaction down the series.

If the outer shell had seven electrons, the tendency would be to gain rather than lose electrons to reach a full octet, which would make the substance far less reactive with water. A full outer shell is characteristic of very unreactive, stable species. Noble gases have full outer shells and are largely inert, so they don’t react with water.