Final answer:
Magnesium is most likely to be chemically and physically similar to aluminum.
Step-by-step explanation:
Magnesium (Mg) is most likely to be chemically and physically similar to aluminum (Al). Both elements belong to Group 2 in the periodic table, known as the alkaline earth metals. They have similar electronic configurations, with 2 valence electrons in the outermost s subshell. This similarity in electron configuration leads to similar chemical properties.