باريوم (Ba)

الاكتشاف والتاريخ

تاريخ الاكتشاف: 1808 · Carl Wilhelm Scheele

Alchemists in the early Middle Ages knew about some barium minerals. Smooth pebble-like stones of mineral baryte were found in volcanic rock near Bologna, Italy, and so were called "Bologna stones". Alchemists were attracted to them because after exposure to light they would glow for years. The phosphorescent properties of baryte heated with organics were described by V. Casciorolus in 1602. Carl Scheele determined that baryte contained a new element in 1772, but could not isolate barium, only barium oxide. Johan Gottlieb Gahn also isolated barium oxide two years later in similar studies. Oxidized barium was at first called "barote" by Guyton de Morveau, a name that was changed by Antoine Lavoisier to baryte (in French) or baryta (in Latin). Also in the 18th century, English mineralogist William Withering noted a heavy mineral in the lead mines of Cumberland, now known to be witherite. B

الاستخدامات والتطبيقات

Barium salts are typically white when solid and colorless when dissolved. They are denser than the strontium or calcium analogs (see table; zinc is given for comparison). Barium hydroxide ("baryta") was known to alchemists, who produced it by heating barium carbonate. Unlike calcium hydroxide, it absorbs very little CO2 in aqueous solutions and is therefore insensitive to atmospheric fluctuations. This property is used in calibrating pH equipment. Barium compounds burn with a green to pale green flame, which is an efficient test to detect a barium compound. The color results from spectral lines at 455.4, 493.4, 553.6, and 611.1 nm.

النظائر

All nuclear data not otherwise stated is from the standard source: Barium found in the Earth's crust is a mixture of seven primordial nuclides, barium-130, 132, and 134 through 138. Barium-130 undergoes very slow radioactive decay to xenon-130 by double beta plus decay, with a half-life of (0.5–2.7)×1021 years (about 1011 times the age of the universe). Its abundance is about 0.11% that of natural barium. Though barium-132 can theoretically undergo the same decay, giving xenon-132, experimental evidence has not detected this. Of the stable isotopes, barium-138 composes 71.7% of all barium; other isotopes have decreasing abundance with decreasing mass number (except for a probable inversion for the p-nuclei 130Ba and 132Ba). In total, barium has 41 known isotopes, ranging in mass between 114 and 154. The most stable artificial radioisotope is barium-133 with a half-life of 10.538 years. F