- noun a soft silvery radioactive element that reacts strongly with water and ignites in air, used in photocells and glass manufacture
- A soft silver-white metal whose atomic number is 37. It is extremely reactive, forming compounds with most every element, reacts vigorously with water, and may ignite when exposed to air. It is the most electropositive element after cesium, becomes a liquid at temperatures above 39°, and has around 30 known isotopes, of which one is stable. It is used in photocells, as a getter in vacuum tubes, in atomic clocks, and in special glasses. Its chemical symbol is Rb.
- chemical symbol Rb
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