Final answer:
The set of elements with the most similar physical and chemical properties is Chlorine (Cl), Bromine (Br), and Iodine (I), all of which are halogens with seven valence electrons leading to similar reactivity, such as forming salts with metals like sodium.
Step-by-step explanation:
The set of elements that has the most similar physical and chemical properties among the ones listed is Chlorine (Cl), Bromine (Br), and Iodine (I), which are all halogens. Halogens are known for having similar properties due to their place in the periodic table; they belong to Group 17, which is known for elements with seven valence electrons. This configuration leads to similar reactivity patterns among the halogens, such as their tendency to form salts with metals. For instance, they all react with elements like sodium to form similar compounds, such as sodium chloride (table salt), sodium bromide, and sodium iodide.
In comparison, the other sets of elements listed either do not belong to the same group or their physical and chemical properties are not as closely aligned as the halogens. For example, although Hydrogen (H), Lithium (Li), and Sodium (Na) are all placed in Group 1 (alkali metals), hydrogen is not a metal and does not share all the characteristics of alkali metals like lithium and sodium. Similarly, Carbon (C), Nitrogen (N), and Oxygen (O) are all nonmetals and neighbors on the periodic table, but they have distinct chemical behaviors. Aluminum (Al), Silicon (Si), and Phosphorus (P) also do not have as congruent properties as elements within the same group, like the halogens.