Which of the following describes the property of elements that are in the same group in the periodic table?

Elements that are in the same group of the periodic table share the same number of valence electrons in their outermost electron shell. This characteristic is significant because it largely determines the chemical properties and reactivity of the elements. For instance, all the alkali metals (found in Group 1) have one valence electron, which makes them highly reactive and results in similar chemical behavior. Similarly, the elements in Group 17, the halogens, have seven valence electrons, contributing to their tendency to react with metals.

In contrast, while some elements in the same group may have similar atomic masses, they don’t necessarily have identical atomic masses or the same number of neutrons, as atomic mass can vary widely among the isotopes of an element. Additionally, having identical physical properties is not a requirement for group members; rather, they may exhibit a range of physical properties such as boiling and melting points. Thus, the defining characteristic of elements in the same group is their commonality in the number of valence electrons, which directly influences their chemical interactions.