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Which alkaline-earth metal is hard enough to scratch glass?

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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).

Beryllium is the alkaline-earth metal that is sufficiently hard to scratch glass. In contrast, other members of the group, such as barium, are much softer, with hardness levels comparable to lead.1