strontium, barium, and radium have similar electrom configurations
strontium is metallic_element. strontium_oxide is not chemical_compound. strontium_oxide is chemical_compound. protium is unium. protium is not unium. one_of_chemical_elements is strontium. one_of_chemical_elements is not strontium. strontium_ion is not monoatomic_cation. strontium is not metallic_element. strontium_hydroxide is not ionic_compound.