Position of the alkali metals in the periodic table. Downs cell for the electrolysis of molten sodium. The alkali metals. Notice that most of the samples are either stored in mineral oil or sealed in glass tubes to prevent thier reoxidation by atmospheric oxygen.
The images of the alkali metals are adapted from those at en. Individual image credits for the alkali metals are given in reference two at the end of this page.
Fr not determined 0. References 1. The reaction becomes more vigorous as one moves from top to bottom in Group 1A: lithium sizzles fiercely in water, a small amount of sodium reacts even more vigorously, and even a small amount of potassium metal reacts violently and usually ignites the hydrogen gas; rubidium and cesium explode. This is a result of the fact that the size of the element increases as we move down the group: as the size of the metal increases, the valence electron is farther away from the nucleus, and is thus more easily removed i.
Although hydrogen is placed at the top of Group 1A in most versions of the periodic table, it is very different from the other members of the alkali metal group. In its elemental form, hydrogen is a colorless, odorless, extremely flammable gas at room temperature, consisting of diatomic molecules of H 2.
Under tremendous pressure about 2 million atmospheres , it can be converted to a metallic form, capable of conducting electricity. It has been theorized that center of the planet Jupiter consists of metallic hydrogen. In the Earth's crust, it is found at a concentration of ppm mostly in the form water and of organic compounds , making it the 10th most abundant element.
Of course, there's also "dark matter" and "dark energy" to worry about, but that's another story. Hydrogen, helium, and trace amounts of lithium were produced at the beginning of the Universe in the Big Bang, and became concentrated into stars by the force of gravity.
The fusion of hydrogen and its isotopes see below also powers the hydrogen bomb, which contains lithium deuteride LiD and tritium; the explosion of a fission-powered bomb produces neutrons which initiate fusion of the deuterium with the tritium, releasing vast amounts of energy.
Research into achieving controlled nuclear fusion to generate electricity is being conducted, but the extremely high temperatures that are necessary to initiate the fusion reactions present a major challenge to physicists. Hydrogen typically does not form cations, but instead forms compounds through covalent bonding.
Hydrogen can form bonds to many other elements, such as nitrogen NH 3 and its derivatives , oxygen H 2 O and sulfur H 2 S , the halogens HX , and carbon, where it is found in millions of different hydrocarbons and other organic molecules almost all organic molecules contain at least some hydrogen atoms. Hydrogen can also bond to metal atoms, such as lithium LiH , calcium CaH 2 , etc. In these compounds, the bonding is usually pictured as a metal cation combined with a hydride anion H -.
On some periodic tables, in fact, hydrogen is placed at the top of Group 7A, since like the halogens, it can form a -1 charge. Hydrogen is also found in acids , which are molecules containing easily-removed hydrogen atoms, usually connected to oxygen, nitrogen, or a halogen.
This is a greatly oversimplified explanation of acid-base chemistry. Hydrogen was discovered by the English chemist Henry Cavendish in ; hydrogen had been observed before, but Cavendish was the first to recognize not only that it was an element, but that it burned to form water, which also provided conclusive proof that water was not itself an element.
The name "hydrogen" was derived by the French chemist Antoine Lavoisier from the Greek words hydro "water" and genes "forming". There are three isotopes of hydrogen. Hydrogen-1, or protium , contains one proton in its nucleus, and is by far the most common form of hydrogen Hydrogen-2, or deuterium , contains one proton and one neutron in its nucleus, and comprises the remaining 0.
Hydrogen-3, or tritium , contains one proton and two neutrons, and is only found in trace amounts; it is produced by the interaction of cosmic rays on gases in the upper atmosphere, and in nuclear explosions, but since it has a half life of only Heavy water is water made from two atoms of deuterium and one atom of oxygen. This form of water is literally heavier than "ordinary" water, since an atom of deuterium is twice as heavy as an atom of "regular" hydrogen.
H 2 O has a molar mass of Ordinary water contains about 1 molecule of D 2 O for every molecules of H 2 O. The electrolysis of water concentrates D 2 O in the solution, since the lighter isotope evaporates from the solution slightly faster.
Successive electrolysis experiments allow pure heavy water to be produced, but it takes about , gallons of water to produce 1 gallon of heavy water by this method. Heavy water is used as a moderator in nuclear reactions: it slows down fast-moving neutrons, allowing them to be captured more easily by other nuclei.
The generation of heavy water was important during the research on nuclear fission that went into the Manhattan Project during World War II. For a typical person, a fatal dose would require drinking nothing but heavy water for 10 to 14 days, so it's pretty doubtful that heavy water poisoning will be featured on CSI anytime soon. Most hydrogen is prepared industrially be reacting coal or hydrocarbons with steam at high temperatures to produce carbon monoxide and hydrogen gas a mixture of carbon monoxide and hydrogen is called synthesis gas , and can be used in manufacturing methanol.
On smaller scales it can be produced by the reaction of active metals such as zinc, calcium, etc. Hydrogen gas is combined with nitrogen in the Haber process to synthesize ammonia NH 3 , which is widely used in fertilizers. It is also used in the manufacture of hydrogenated vegetable oils; in this reaction, hydrogen atoms add to the carbon-carbon double bonds in the vegetable oils double-bonded carbons bond to fewer hydrogen atoms than single-bonded carbons — i.
Another use for hydrogen is in rocket fuels: the Saturn V rockets that launched the Apollo lunar missions used , gallons of kerosene and , gallons of liquid oxygen in its first stage S-IC , , gallons of liquid hydrogen and 83, gallons of liquid oxygen in its second stage S-II , and 69, gallons of liquid hydrogen and 20, gallons of liquid oxygen in its third S-IVB stage; the Space Shuttle main engines use , gallons of liquid hydrogen and , gallons of liquid oxygen.
Hydrogen is lighter than air, and was used in balloons and dirigibles also known as airships or zeppelins. They can all be cut easily with a plastic knife due to their softness, and their shiny surface tarnishes rapidly in air due to oxidation. Because of their high reactivity, alkali metals must be stored under oil to prevent reaction with air.
In the modern IUPAC nomenclature, the alkali metals comprise the group 1 elements, excluding hydrogen.
All the alkali metals react with water, with the heavier alkali metals reacting more vigorously than the lighter ones. This group lies in the s-block of the periodic table, as all alkali metals have their outermost electron in an s-orbital. The alkali metals provide the best example of group trends in properties in the periodic table, with elements exhibiting similar properties.
For instance, when moving down the table, all known alkali metals show:. Unauthorized duplication or posting on other web sites is expressly prohibited. Send suggestions, comments, and new entry desires include the URL if applicable to us by email. Disclaimer : The information contained herein is believed to be true and accurate, however ILPI makes no guarantees concerning the veracity of any statement. Use of any information on this page is at the reader's own risk. ILPI strongly encourages the reader to consult the appropriate local, state and federal agencies concerning the matters discussed herein.
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