Which group of metals consists of lithium, sodium, potassium, and cesium?

The group of metals that includes lithium, sodium, potassium, and cesium is known as the alkali metals. These elements are characterized by their single electron in the outermost shell, which makes them highly reactive, especially with water. Alkali metals are found in Group 1 of the periodic table and exhibit similar chemical properties due to their similar electron configuration.

When these metals react, they tend to lose that one valence electron, forming positive ions with a +1 charge. This reactivity increases down the group; for example, cesium is much more reactive than lithium. The alkali metals are known for forming strong bases when they react with water, leading to the generation of hydroxides and hydrogen gas.

In contrast, alkaline earth metals, located in Group 2, include elements such as magnesium and calcium, and possess two valence electrons. Noble gases, found in Group 18, are characterized by their lack of reactivity due to having a full outer electron shell. Transition metals, which are located in the central block of the periodic table, typically have variable valence electrons and exhibit a range of oxidation states. The distinct properties of alkali metals clearly define them from these other groups.