Certain Period 2 Elements Exhibit Behaviors Similar to Period 3

Multiple Choice

Certain Period 2 elements exhibit behaviors similar to Period 3 elements immediately below and to the right. One of these interesting diagonal relationships occurs between lithium and magnesium. Which of the following is one of their similarities?

A) They both form insoluble carbonate salts.
B) Both elements are important in treating manic-depression.
C) Their first ionization energies are almost equal.
D) Their densities are very similar.
E) They both form organic compounds with polar covalent bonds from the metal to hydrocarbon group.