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Which alkaline-earth metal has the highest atomic number?

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A color-coded periodic table of the elements displays each element's symbol and atomic number, with categories such as alkali metals, noble gases, halogens, transition metals, and actinoid elements distinguished by different background colors.
alkaline-earth metal Modern version of the periodic table of the elements (printable).

The alkaline-earth metal with the highest atomic number is radium (Ra), which has an atomic number of 88.12

As a member of Group 2 of the periodic table, radium is the heaviest of the alkaline-earth metals, a group that also includes beryllium, magnesium, calcium, strontium, and barium. Unlike the other elements in this group, all isotopes of radium are radioactive.321