Chemistry Regents Practice Test 2026 – Complete Prep Resource

An alkali metal is defined as a metal from Group 1 of the periodic table, characterized by having one electron in their outermost shell. This configuration makes alkali metals highly reactive, particularly with water, leading to the formation of hydroxides and the release of hydrogen gas.

Potassium (K) is indeed an alkali metal, positioned in Group 1. It exhibits typical alkali metal properties, such as being soft enough to cut with a knife and having a low melting point compared to most metals. When potassium reacts with water, it produces potassium hydroxide and hydrogen gas, demonstrating the reactive nature common to alkali metals.

In contrast, the other options represent different groups of elements. Calcium (Ca) is an alkaline earth metal, found in Group 2, and it has two electrons in its outer shell. Iron (Fe) is a transition metal located in the center of the periodic table, while copper (Cu) is also a transition metal found in Group 11. Both of these metals exhibit different properties and reactivities compared to alkali metals. Therefore, potassium is the correct answer as it exemplifies the typical characteristics of alkali metals.