Which element in the modern periodic table has the same number of valence electrons as that of caesium?

Explanation

Caesium and potassium are Group 1 elements with one electron in their outermost shells: Cs has 6s¹ and K has 4s¹. Aluminium has three outer-shell electrons, while barium and calcium have two. Potassium therefore matches caesium’s valence-electron count.