Use a periodic table to choose the pair of elements whose properties are most similar.
A. silicon (Si), phosphorus (P)
B. neon (Ne), sulfur (S)
C. potassium (K), magnesium (Mg)
D. chlorine (CI), iodine (I)

Silicon and Phosphorus

Explanation:

They are right next to each other and would have the closest similarities in the case of: Atomic Weight, Density, Oxidation States, Phase, Period, and their Atomic radius

substituting a hydrogen atom with a halogen in a hydrocarbon:

- the single bond remains single. a is wrong.

- the bond with hydrogen is as strong as with a halogen. c is wrong

- a hydrocarbon is saturated if there is no double bond. we do not know that so d is wrong.

- carbon will always have four valence electrons. e is wrong.

by elimination, the correct answer is b. the boiling point of the new compound increases.