How do the properties of elements in the same family or group in the periodic table compare?

The correct choice emphasizes that elements within the same family or group in the periodic table exhibit similar arrangements of electrons, particularly in their outermost shell. This configuration plays a crucial role in determining the chemical properties and reactivity of the elements. For example, all elements in Group 1 (the alkali metals) have one electron in their outer shell, which grants them similar behavior in reactions, such as their tendency to lose that electron easily and form +1 ions.

In contrast, the other options do not accurately represent the characteristics of elements in the same group. Atomic masses vary widely among elements in a group due to differences in the number of protons and neutrons. While some groups may contain gases at room temperature (like the noble gases), this is not universally true for all groups, such as the alkali metals or alkaline earth metals, which are solids. Additionally, while some elements form ionic bonds, not all elements within the same group necessarily do; bonding behaviors can vary based on additional factors beyond group affiliation. Focusing on the electron arrangement explains the similarities in chemical behavior and provides a foundational understanding of the periodic trends.