Question

which pair of elements from those outlined has the greatest difference in chemical properties?
a. potassium (k) and francium (fr)
b. thallium (tl) and gallium (ga)
c. neon (ne) and radon (rn)
d. krypton (kr) and strontium (sr)

Explanation:

Step1: Recall periodic - table trends

Elements in different groups and periods have different chemical properties. Groups have similar chemical properties due to the same number of valence electrons.

Step2: Analyze option A

Potassium (K) and francium (Fr) are in the same group (Group 1 - alkali metals), so they have similar chemical properties.

Step3: Analyze option B

Thallium (Tl) and gallium (Ga) are in the same group (Group 13), so they have similar chemical properties.

Step4: Analyze option C

Neon (Ne) and radon (Rn) are in the same group (Group 18 - noble gases), so they have similar chemical properties.

Step5: Analyze option D

Krypton (Kr) is a noble gas (Group 18) and strontium (Sr) is an alkaline - earth metal (Group 2). They are in different groups and have very different chemical properties.

Answer:

D. krypton (Kr) and strontium (Sr)