Question

which pair of elements from those outlined has the greatest difference in chemical properties?

Explanation:

Step1: Recall periodic - table trends

Elements in different groups and periods have different chemical properties. The further apart elements are in the periodic table in terms of group and period, the more likely they are to have different chemical properties.

Step2: Analyze outlined elements

Metals and non - metals have very different chemical properties. Among the outlined elements, metals like alkali metals (e.g., K, Rb, Cs, Fr) and non - metals like halogens (e.g., F, Cl, Br, I, At) are far apart in terms of chemical behavior.

Step3: Determine the pair

A pair such as an alkali metal and a halogen would have a large difference in chemical properties. For example, the reaction of an alkali metal (highly reactive, easily losing an electron) with a halogen (highly reactive, easily gaining an electron) is very vigorous.

Answer:

A pair consisting of an alkali metal and a halogen from the outlined elements would have the greatest difference in chemical properties.