ASMEPPS Science Practice Test 2025 - Free Science Practice Questions and Study Guide

Alkali earth metals are characterized by having two valence electrons in their outermost electron shell. This configuration is a result of their position in Group 2 of the periodic table. The presence of these two valence electrons significantly influences their chemical properties and reactivity. For example, alkali earth metals tend to form positive ions with a +2 charge by losing these two electrons during chemical reactions. This characteristic also explains their typical bonding behavior, as they readily interact with nonmetals to achieve a stable electron configuration. The stability of having two valence electrons enables them to react less vigorously than their alkali metal counterparts, which have one valence electron. Thus, the defining trait of alkali earth metals is indeed their two valence electrons, making this the correct answer.