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HydrogenÂ hasÂ theÂ smallest atoms of any element. A hydrogen atom contains one proton, a tiny particle with a positive electrical charge, and only one electron, a negatively charged particle. Pure hydrogen exists as hydrogen gas in which pairs of hydrogen atoms bond together to make larger particles called molecules.
It is by far the most abundant element in the universe and makes up about 90% of the universe by weight, it is usually found in compounds.
Hydrogen has an atomic number of 1 and atomic weight of 1.00794
Meaning of Name
Hydrogen gas is odorless, tasteless, colorless, and highly flammable. When hydrogen gas burns in air it forms water. It burns in air to form only water as waste product.
French chemist Antoine Lavoisier named hydrogen from the Greek words for "water former."
EarlyÂ chemistsÂ confused hydrogen with other gases until British physicist and chemist Henry Cavendish described the properties of hydrogen gas in the mid-1700s. Many scientists before Cavendish had made the flammable gas by mixing metals with acids. Cavendish called the gas flammable air and studied it. He demonstrated in 1766 that sulfuric acid reacted with metals to produce flammable air. Later, Cavendish burned his flammable air in regular air to produce water, and only water. Many historians consider Cavendish to be the principle discoverer of hydrogen gas, although Scottish engineer James Watt reported that he had produced water at about the same time as Cavendish.
Position in Periodic Table
HydrogenÂ isÂ theÂ first element in the periodic table of the elements and is represented by the symbol H. Hydrogen, with only one proton, is the simplest element. It is usually placed in Period 1 (the first row) and Group 1 (the first column) of the periodic table, it can be found in the s-block of the periodic table. Hydrogen can combine chemically with almost every other element and forms more compounds than does any other element. These compounds include water, minerals, and hydrocarbons such as petroleum and natural gas.
Water: 2H2 + O2 2H2O
Minerals: H2 + Cl2 2HCl
Hydrocarbons: 3H2 + 2C C2H6
PureÂ hydrogenÂ gasÂ isÂ rare, so chemists produce it in the laboratory and in chemical factories. They can produce it in a variety of ways. Producing extremely pure hydrogen gas involves a process called hydrolysis. In this process, a chemist passes an electrical current through water to break the water molecules up into hydrogen gas and oxygen gas:
2H2OÂ +Â electricalÂ energy â†’ 2H2 + O2
ThisÂ chemicalÂ equation shows those two water molecules (H2O), with electricity, form two molecules of hydrogen gas (H2) and one molecule of oxygen gas (O2). Early chemists made hydrogen gas by reacting a metal with an acid. One example of such a reaction occurs between zinc (Zn) and hydrochloric acid (HCl). The chemical equation for this reaction is the following:
ZnÂ +Â 2HClÂ â†’Â ZnCl2Â +Â H2
InÂ theÂ chemicalÂ industry, hydrogen forms in other reactions, such as in the production of chlorine (Cl2) and sodium hydroxide (NaOH) from sodium chloride dissolved in water (NaCl in H2O). In petroleum refineries, hydrogen forms as a by-product from hydrocarbon processing.
TheÂ chemicalÂ industry uses hydrogen gas in many industrial chemical processes. The most important of these processes uses hydrogen to make ammonia (NH3); it is called the Haber process after German chemist Fritz Haber, who developed it in 1908. The industry can then use ammonia to make other important products, such as explosives and fertilizers. Industrial chemists also use hydrogen in large amounts to make compounds such as the fuel methane (CH4) and the alcohol methanol (CH3OH), which is used as antifreeze and to make other chemicals. The food industry hydrogenates (adds hydrogen to) liquid oils (see Hydrogenation). When hydrogen atoms are added to the molecules of liquid oils, the oils become solid fats, such as margarine or vegetable shortening (for example, Crisco). Metallurgists use hydrogen to separate pure metals from their oxides. For example, hydrogen bonds with and removes oxygen from copper oxide, leaving pure copper.
HydrogenÂ existsÂ inÂ nature as three different isotopes. Isotopes are atoms of the same element that contain different numbers of neutrons, uncharged elementary particles, in their nuclei. The majority of hydrogen atoms have no (zero) neutrons in their nuclei. Scientists represent these hydrogen atoms with the symbol 1H. Atoms of 1H have just one proton in their nucleus and have an atomic mass of 1. This isotope, which accounts for 99.98 percent of hydrogen atoms, is sometimes called protium. About 0.02 percent of hydrogen atoms have one neutron and one proton in their nucleus. This isotope is called deuterium.
TheÂ isotopesÂ deuterium and tritium were discovered in the 20th century. British physicist Francis W. Aston invented a mass spectrograph that separates atoms by their masses. He found atoms with masses that were unusual, namely the isotopes. This provided the first clue to the existence of deuterium. In 1932 American chemist Harold C. Urey and his associates isolated and discovered deuterium. Urey predicted that water made with deuterium would evaporate more slowly than would water made with protium and was, in this way, able to separate and isolate the deuterium. Scientists first produced tritium in 1935 by bombarding deuterium with deuterium nuclei (one proton and one neutron). Scientists have since found tritium in very small amounts in ordinary water. Tritium forms naturally in some atmospheric reactions.
The Hydrogen isotope H-2, also known as deuterium, is used in a variety of applications. Deuterium is used extensively in organic chemistry in order to study chemical reactions. It is also used in vitamin research. Deuterium in the form of H2O is known as heavy water, it is used in NMR studies and in studies into human metabolism.
Below are symbols of the various isotopes of Hydrogen
PureÂ hydrogenÂ isÂ aÂ gas under normal conditions-that is, at room temperature and normal atmospheric pressure. Like most gaseous elements, hydrogen is diatomic, meaning its molecules contain two atoms. Molecular hydrogen is represented symbolically as H2. Hydrogen gas is much lighter than air. At 0Â°C (273K) and regular atmospheric pressure, hydrogen has a relative density of 0.090 grams/liter (g/L), whereas the relative density of ordinary air is 1.0 g/L. Hydrogen has such a small mass that it can escape Earth's gravitational pull and fly off into space. As a result, it is not found in large amounts in the atmosphere. Hydrogen has a lower boiling point and freezing point than does any other substance except helium. Hydrogen boils at -252.8Â°C and freezes at -259.14Â°C.
Deuterium was the first isotope of any element that scientists discovered and isolated from a sample. It is used in a variety of scientific experiments. Deuterium is represented by the symbol 2H, or by the symbol D, and has an atomic mass of 2. The third isotope of hydrogen is called tritium (3H). This isotope has two neutrons and one proton in each atom's nucleus, and it has an atomic mass of 3. Tritium accounts for less than one in 10,000 atoms of hydrogen. It is radioactive, meaning its nucleus can decay, or spontaneously change, into other particles (see Radioactivity). The half-life of a radioactive substance, such as tritium, is the length of time necessary for half of a sample of the substance to decay into other particles. Tritium has a half-life of 12.4 years. Scientists can make tritium in the laboratory in nuclear reactions. The names protium, deuterium, and tritium come from the Greek words for first, second, and third, respectively.