Magnesium (Mg) is the element that is most likely to have similar properties to calcium (Ca). This is because both calcium and magnesium are classified as alkaline earth metals, which are found in Group 2 of the periodic table. Alkaline earth metals share similar chemical and physical properties, including reactivity, ionization energy, and common oxidation states.
In contrast:
- Potassium (K) is an alkali metal from Group 1, which has different properties compared to alkaline earth metals.
- Scandium (Sc) is a transition metal from Group 3 and has a different set of properties than alkaline earth metals.
- Argon (Ar) is a noble gas and does not share properties with calcium, which is a metal.
Thus, the correct answer is Magnesium (Mg), because they are both alkaline earth metals.