Is potassium (K) more similar to rubidium (Rb) or calcium (Ca) ? Why?

A: Calcium because it has one more proton than potassium while rubidium has 18 more protons than potassium.

B: Rubidium because they have the same number of valence electrons

C: Calcium because it has one more valence electron than potassium

D: Rubidium because they have the same number of electrons.

Answer: option B: Rubidium because they have the same number of valence electrons.

Explanation:

Potassium and Rubidium are both alkayne metals. They belong to the group 1 of the periodic table and, hence, have the same number of valence electrons, while Calcium belongs to the group 2.

Remember that the elements are grouped in the periodic table according their properties. Elements in the same group have similar properties.

The similarity of the elements in the same group of the periodic table is explained by having the same number of valence electrons, as it is the valence electrons what determines the formation of chemical bonds and so many chemical and physical properties.

Potassium and cesium have 1 valence electron each, while calcium has 2 valence electrons.