Radium, symbolized as Ra, is a naturally occurring element. Its discovery marked a turning point in science, revealing the power contained within the atomic nucleus. This silvery-white metal possesses a unique combination of chemical properties and powerful radiation, making its position on the periodic table significant.
Radium’s Identity on the Periodic Table
Radium is element number 88 on the periodic table, meaning every atom contains 88 protons in its nucleus. This atomic number defines the element, distinguishing it from all others. Radium is situated in Group 2, making it the heaviest naturally occurring alkaline earth metal. This placement indicates it possesses two valence electrons, making it highly reactive. Its position in the seventh period reflects that its electrons occupy seven principal energy levels.
Radium’s chemical behavior is similar to its lighter counterparts, particularly barium. The element readily forms compounds where it loses its two outer electrons to achieve a stable configuration. Pure radium is silvery-white, but it quickly reacts with nitrogen in the air to form a black surface layer of radium nitride.
The Nature of Radium’s Radioactivity
Radium’s defining feature is its powerful radioactivity, stemming from its unstable atomic nucleus. All 33 known isotopes of radium are radioactive, spontaneously transforming into other elements by emitting high-energy particles. The most common and longest-lived isotope is Radium-226, which has a half-life of approximately 1,600 years. This half-life is significantly shorter than that of its parent, Uranium-238, making Radium intensely radioactive.
Radioactive decay involves the nucleus ejecting various types of radiation, including alpha particles, beta particles, and gamma rays. Radium-226 primarily decays by emitting an alpha particle, transforming into the radioactive gas Radon-222. The energy released is so intense that pure radium compounds exhibit a faint blue glow in the dark, caused by the radiation exciting the surrounding air. A sample of radium maintains a temperature slightly higher than its surroundings due to this continuous energy release.
Historical Discovery and Early Applications
Radium was discovered in 1898 by Marie and Pierre Curie, who were studying the intense radioactivity of the uranium ore pitchblende. They realized that the ore was far more radioactive than could be accounted for by the uranium content alone, suggesting a new element was present. Through a laborious process of fractional crystallization, they were eventually able to isolate minute amounts of radium chloride from tons of the raw ore. The name Radium comes from the Latin word radius, meaning “ray,” in recognition of the energy it emitted.
The powerful radiation and the element’s persistent glow led to a wide variety of early applications. Radium was famously used in self-luminous paints for watch dials, aircraft switches, and instrument panels, often mixed with zinc sulfide. Early medical researchers also explored its use in cancer treatment, where radium needles were implanted into tumors. However, its widespread use in consumer products, like health tonics and cosmetics, ended when the severe toxicity and long-term health hazards from radiation exposure became apparent.