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Commercial rubidium clocks are less accurate than caesium atomic clocks, which serve as primary frequency standards, so a rubidium clock is usually used as a secondary frequency standard. Commercial rubidium frequency standards operate by disciplining a crystal oscillator to the rubidium hyperfine transition of 6.8 GHz (6 834 682 610.904 Hz).
The dates indicate the true age of the minerals only if the rocks have not been subsequently altered. See rubidium–strontium dating for a more detailed discussion. Other than 87 Rb, the longest-lived radioisotopes are 83 Rb with a half-life of 86.2 days, 84 Rb with a half-life of 33.1 days, and 86 Rb with a half-life of 18.642 days. All other ...
Zinc is a chalcophile, meaning the element is more likely to be found in minerals together with sulfur and other heavy chalcogens, rather than with the light chalcogen oxygen or with non-chalcogen electronegative elements such as the halogens. Sulfides formed as the crust solidified under the reducing conditions of the early Earth's atmosphere ...
Manganese(IV) oxide was used in the original type of dry cell battery as an electron acceptor from zinc, and is the blackish material in carbon–zinc type flashlight cells. The manganese dioxide is reduced to the manganese oxide-hydroxide MnO(OH) during discharging, preventing the formation of hydrogen at the anode of the battery. [82]