Because both isotopes of chlorine have 17 positive protons in the nucleus and 17 negative protons from electrons in the surrounding orbitals, it doesn’t matter which isotope is present in a chemical reaction.Ĭonsider a chlorine atom, which has 17 protons and has two isotopes: chlorine 35 and chlorine 37. Relative atomic mass = ( 75 100 35) + ( 25 100 37) =35.5īecause neutrons have no charge, all isotopes of any element act chemically the same. The atomic weight, or relative atomic mass, is a weighted average of the weights of all chlorine isotopes. When the mass of chlorine is determined with a mass spectrometer, the result is 35.5. That means there is 75 percent Chlorine-35 and 25% Chlorine-37 in any pure chlorine mixture that can be isolated from all other elements. Chlorine-37 has 17 protons and 20 neutrons and is found about 25% of the time in nature. Chlorine comes in two forms: chlorine-35 and chlorine-37.Ĭhlorine-35, which has 17 protons and 18 neutrons, is found in nature roughly 75% of the time. Isotopes are atoms that have the same number of protons (17 in the case of chlorine) but variable numbers of neutrons. Free hydrochloric acid is present in the stomach.Why is the atomic mass of chlorine taken as 35.5 u and not a whole number like 35 u or 36 u explain?īecause of something called isotopes, chlorine has an atomic weight of 35.5 instead of 35. It is found in evaporite minerals such as chlorapatite and sodalite. Other chlorine-containing minerals are sylvite ( potassium chloride ), bischofite (MgCl 2 ∙6H 2O), carnallite (KCl∙MgCl 2 ∙6H 2O), and kainite (KCl∙MgSO 4 ∙3H 2O). Small quantities of sodium chloride are present in blood and in milk. Certain landlocked seas, such as the Caspian Sea, the Dead Sea, and the Great Salt Lake of Utah, contain up to 33 percent dissolved salt. Sodium chloride is also present in seawater, which has an average concentration of about 2 percent of that salt. The most common compound of chlorine is sodium chloride, which is found in nature as crystalline rock salt, often discoloured by impurities. Natural chlorine is a mixture of two stable isotopes: chlorine-35 (75.53 percent) and chlorine-37 (24.47 percent). It constitutes 0.017 percent of Earth’s crust. Occurrence and distributionĪpart from very small amounts of free chlorine (Cl) in volcanic gases, chlorine is usually found only in the form of chemical compounds. The true nature of the gas as an element was recognized in 1810 by English chemist Humphry Davy, who later named it chlorine (from the Greek chloros, meaning “yellowish green”) and provided an explanation for its bleaching action. In 1774 the Swedish chemist Carl Wilhelm Scheele treated powdered black oxide of manganese with hydrochloric acid and obtained a greenish-yellowish gas, which he failed to recognize as an element. Later he obtained the same product, now known to be hydrochloric acid, by heating salt with sulfuric acid. In 1648 the German chemist Johann Rudolf Glauber obtained a strong acid, which he called spirit of salt, by heating moist salt in a charcoal furnace and condensing the fumes in a receiver. In Roman times, soldiers were partially paid in salt ( salarium, the root of the modern word salary). It is the main constituent of the salts dissolved in seawater, from which it was obtained in ancient Egypt by evaporation. Rock salt (common salt, or sodium chloride) has been known for several thousand years. Ionic bond: sodium chloride, or table salt SpaceNext50 Britannica presents SpaceNext50, From the race to the Moon to space stewardship, we explore a wide range of subjects that feed our curiosity about space!.Learn about the major environmental problems facing our planet and what can be done about them! Saving Earth Britannica Presents Earth’s To-Do List for the 21st Century. Britannica Beyond We’ve created a new place where questions are at the center of learning.100 Women Britannica celebrates the centennial of the Nineteenth Amendment, highlighting suffragists and history-making politicians.COVID-19 Portal While this global health crisis continues to evolve, it can be useful to look to past pandemics to better understand how to respond today.Student Portal Britannica is the ultimate student resource for key school subjects like history, government, literature, and more.
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