Nursing Entrance Exam (NEX) 2025 – 400 Free Practice Questions to Pass the Exam

The element that reacts most readily with sodium is potassium. Both sodium and potassium belong to the alkali metal group in the periodic table, which means they share similar chemical properties, particularly their tendency to engage in reactions.

When considering reactivity, the trend in the alkali metals shows that as you move down the group, from lithium to cesium, the reactivity increases. This is due to the increasing atomic size and the resultant decrease in ionization energy. Since potassium is directly below sodium in the periodic table, it is more reactive than sodium itself. Thus, when sodium is placed in contact with potassium, a reaction is likely to occur vigorously.

In contrast, boron, helium, and chlorine have different reactivity levels: boron is a metalloid with less reactivity than alkali metals, helium is a noble gas and is chemically inert under normal conditions, and chlorine, while a non-metal that can react with sodium, does not react as readily as potassium does in terms of alkali metal interactions. The strong reactivity of potassium with sodium exemplifies why potassium is the most reactive choice in this context.