Final answer:
Elements in the same group on the periodic table exhibit similar chemical properties due to their identical number of valence electrons, dictating their typical reactions and chemical behaviors.
The correct option is C.
Step-by-step explanation:
The elements in a group on the periodic table exhibit similar chemical properties because they have the same number of valence electrons in their outermost energy levels. This uniformity in valence electrons leads to similar chemical behaviors, such as the tendency to gain, lose, or share electrons in chemical reactions, which defines an element's reactivity.
For instance, the alkali metals like lithium and sodium each have one valence electron, while the halogens like fluorine and chlorine each have seven valence electrons. This similarity is why elements of the same group have comparable chemical properties.
The atomic structure of an element, particularly the electron configuration, underlies much of its chemistry. Since the periodic table arranges elements according to increasing atomic number and similar electron configurations fall in the same groups, the table's structure reflects the elements' chemical properties.
The correct option is C.