Overview
Definition of cesium 133: an isotope of cesium used especially in atomic clocks and one of whose atomic transitions is used as a scientific time standard First Known Use of cesium 133 1966, in the meaning defined above. There are 52 isotopes and isomers of cesium with masses ranging from 112-148 (1). Cesium-133 is naturally occuring and is stable (2). Cesium -112 through 132 and 134 through 148 are artificially produced and are radioactive (2). (1) Lide DR; CRC Handbook of. Cesium metal is highly reactive, both with water and air, it must be placed in sealed glass ampoule under argon or vacuum only. Caesium metal is the most chemically reactive of all metals, except for the almost non-existing francium. It spontaneously burns in air and explodes when dropped in water. The natural 133Cs isn't radioactive.
Cesium is a member of the alkali family, which consists of elements in Group 1 (IA) of the periodic table. The periodic table is a chart that shows how chemical elements are related to each other. The alkalis include lithium, sodium, potassium, rubidium, and francium. Cesium is considered the most active metal. Although in theory francium is more active than cesium, francium is too rare to have any commercial uses.
Name: Cesium Symbol: Cs Atomic Number: 55 Atomic Mass: 132.90546 amu Melting Point: 28.5 °C (301.65 K, 83.3 °F) Boiling Point: 678.4 °C (951.55005 K, 1253.12 °F) Number of Protons/Electrons: 55 Number of Neutrons: 78 Classification: Alkali Metal Crystal Structure: Cubic Density @ 293 K: 1.873 g/cm 3 Color: silver British Spelling: Caesium.
Cesium was discovered in 1861 by German chemists Robert Bunsen (1811-99) and Gustav Kirchhoff (1824-87). They found the element using a method of analysis they had just invented: spectroscopy. Ubuntu vmware for mac os. Spectroscopy is the process of analyzing light produced when an element is heated. The light produced is different for every element. The spectrum (plural: spectra) of an element consists of a series of colored lines.
SYMBOL
Cs
ATOMIC NUMBER
55
ATOMIC MASS
132.9054
FAMILY
Group 1 (IA)
Alkali metal
PRONUNCIATION
SEE-zee-um
Cesium is not a common element, and it has few commercial uses. One of its radioactive isotopes, cesium-137, is widely used in a variety of medical and industrial applications.
Discovery and naming
The invention of spectroscopy gave chemists a powerful new tool. In many cases, the amount of an element present in a sample is too small to see. But the element is much easier to detect by spectroscopy. When the substance is heated, the hidden elements give off characteristic spectral lines. Using spectroscopy, a chemist can identify the elements by these distinctive lines.
Such was the case with the discovery of cesium. In 1859, Bunsen and Kirchhoff were studying a sample of mineral water taken from a spring. They saw spectral lines for sodium, potassium, lithium, calcium, and strontium. These elements were already well known.
After Bunsen and Kirchhoff removed all these elements from their sample, they were surprised to find two beautiful blue lines in the spectrum of the 'empty' spring water. The water contained an unknown element. Bunsen suggested calling the element cesium, from the Latin word caesius for 'sky blue.' For many years, the name was also spelled caesium.
Physical properties
Cesium is a silvery-white, shiny metal that is very soft and ductile. Ductile means capable of being drawn into thin wires. Its melting point is 28.5°C (83.3°F). It melts easily in the heat of one's hand, but should never be handled that way! Cesium's boiling point is 705°C (1,300°F), and its density is 1.90 grams per cubic centimeter.
Chemical properties
Cesium is a very reactive metal. It combines quickly with oxygen in the air and reacts violently with water. In the reaction with water, hydrogen gas is released. Hydrogen gas ignites immediately as a result of the heat given off by the reaction. Cesium must be stored under kerosene or a mineral oil to protect it from reacting with oxygen and water vapor in the air.
Cesium also reacts vigorously with acids, the halogens, sulfur, and phosphorus.
Cesium 133 Second
Occurrence in nature
The abundance of cesium in the Earth's crust has been estimated at about 1 to 3 parts per million. It ranks in the middle
of the chemical elements in terms of their abundance in the earth.Cesium occurs in small quantities in a number of minerals. It is often found in an ore of lithium called lepidolite. The mineral containing the largest fraction of cesium is pollucite (Cs 4 Al 4 Si 9 O 26 ). This ore is mined in large quantities at Bernic Lake, in the Canadian province of Manitoba. Cesium is also found in small amounts in a mineral of boron called rhodizite.
Isotopes
Only one naturally occurring isotope of cesium is known, cesium-133. Isotopes are two or more forms of an element. Isotopes differ from each other according to their mass number. The number written to the right of the element's name is the mass number. The mass number represents the number of protons plus neutrons in the nucleus of an atom of the element. The number of protons determines the element, but the number of neutrons in the atom of any one element can vary. Each variation is an isotope.
A number of artificial radioactive isotopes of cesium are known also. A radioactive isotope is one that breaks apart and gives off some form of radiation. Radioactive isotopes are produced when very small particles are fired at atoms. These particles stick in the atoms and make them radioactive.
One radioactive isotope of cesium is of special importance, cesium-137. It is produced in nuclear fission reactions. Nuclear fission is the process in which large atoms break apart. Large amounts of energy and smaller atoms are produced during fission. The smaller atoms are called fission products. Cesium-137 is a very common fission product.
Nuclear fission is used in nuclear power plants. The heat produced by nuclear fission can be converted into electricity. While this process is going on, cesium-137 is being produced as a by-product. That cesium-137 can be collected and used for a number of applications.
As an example, cesium-137 can be used to monitor the flow of oil in a pipeline. In many cases, more than one oil company may use the same pipeline. How does a receiving station know whose oil is coming through the pipeline? One way to solve that problem is to add a little cesium-137 when a new batch of oil is being sent. The cesium-137 gives off radiation. That radiation can be detected easily by holding a detector at the end of the pipeline. When the detector shows the presence of radiation, a new batch of oil has arrived.
This isotope of cesium can also be used to treat some kinds of cancer. One procedure is to fill a hollow steel needle with cesium-137. The needle can then be implanted into a person's body. The cesium-137 gives off radiation inside the body. That radiation kills cancer cells and may help cure the disease.
When a hollow steel needle filled with cesium-137 is implanted into a person's body, the isotopes's radiation can kill cancer cells.
Cesium-137 is often used in scientific research also. For example, cesium tends to stick to particles of sand and gravel. This fact can be used to measure the speed of erosion in an area. Cesium-137 is injected into the ground at some point. Some time later, a detector is used to see how far the isotope has moved. The distance moved tells a scientist how fast soil is being carried away. In other words, it tells how fast erosion is taking place.
Cesium-137 has also been approved for the irradiation of certain foods. The radiation given off by the isotope kills bacteria and other organisms that cause disease. Foods irradiated by this method last longer before beginning to spoil. Wheat, flour, and potatoes are some of the foods that can be preserved by cesium-137 irradiation.
Extraction
Cesium can be obtained in pure form by two methods. In one, calcium metal is combined with fused (melted) cesium chloride:
In the other, an electric current passes through a molten (melted) cesium compound:
Uses
Cesium has a limited number of uses. One is as a getter in bulbs and evacuated tubes. The bulb must be as free from gases as possible to work properly. Small amounts of cesium react with any air left in the bulb. It converts the gas into a solid cesium compound. Cesium is called a getter because it gets gases out of the bulb.
Cesium is also used in photoelectric cells, devices for changing sunlight into electrical energy. When sunlight shines on cesium, it excites or energizes the electrons in cesium atoms. The excited electrons easily flow away, producing an electric current.
An important use of cesium today is in an atomic clock. Photo recovery app. An atomic clock is the most precise method now available for measuring time. Here is how an atomic clock works:
Cesium-137 is used in atomic clocks, the most precise method for measuring time.
A beam of energy is shined on a very pure sample of cesium-133. The atoms in the cesium are excited by the energy and give off radiation. That radiation vibrates back and forth, the way a violin string vibrates when plucked. Scientists measure the speed of that vibration. The second is officially defined as that speed of vibration multiplied by 9,192,635,770.
Atomic clocks keep very good time. The best of them lose no more than one second in a million years.
Compounds
Cesium compounds have relatively few commercial uses. Cesium bromide is used to make radiation detectors and other measuring devices. Cesium carbonate and cesium fluoride are used to make specialty glasses. Cesium carbonate and cesium chloride are used in the brewing of beers. Cesium compounds are also used in chemical research.
Cesium 133 Isotope
Health effects
Cesium is not regarded as essential to the health of plants or animals, nor does it present a hazard to them.
The caesium standard is a primary frequency standard in which the photon absorption by transitions between the two hyperfineground states of caesium-133atoms are used to control the output frequency. The first caesium clock was built by Louis Essen in 1955 at the National Physical Laboratory in the UK.[1] and promoted worldwide by Gernot M. R. Winkler of the USNO.
Caesium atomic clocks are the most accurate time and frequency standards, and serve as the primary standard for the definition of the second in the International System of Units (SI) (the modern form of the metric system). By definition, radiation produced by the transition between the two hyperfine ground states of caesium (in the absence of external influences such as the Earth's magnetic field) has a frequency, ΔνCs, of exactly 9192631770Hz. That value was chosen so that the caesium second equalled, to the limit of human measuring ability in 1960 when it was adopted, the existing standard ephemeris second based on the Earth's orbit around the Sun.[2] Because no other measurement involving time had been as precise, the effect of the change was less than the experimental uncertainty of all existing measurements.
Technical details[edit]
The official definition of the second was first given by the BIPM at the 13th General Conference on Weights and Measures in 1967 as: 'The second is the duration of 9192631770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the caesium 133 atom.' At its 1997 meeting the BIPM added to the previous definition the following specification: 'This definition refers to a caesium atom at rest at a temperature of 0 K.'[3]
The BIPM restated this definition in its 26th conference (2018), 'The second is defined by taking the fixed numerical value of the caesium frequency ∆Cs, the unperturbed ground-state hyperfine transition frequency of the caesium 133 atom, to be 9 192 631 770 when expressed in the unit Hz, which is equal to s–1.'[4]
The meaning of the preceding definition is as follows. The caesium atom has a ground state electron state with configuration [Xe] 6s1 and, consequently, atomic term symbol2S1/2. This means that there is one unpaired electron and the total electron spin of the atom is 1/2. Moreover, the nucleus of caesium-133 has a nuclear spin equal to 7/2. The simultaneous presence of electron spin and nuclear spin leads, by a mechanism called hyperfine interaction, to a (small) splitting of all energy levels into two sub-levels. One of the sub-levels corresponds to the electron and nuclear spin being parallel (i.e., pointing in the same direction), leading to a total spin F equal to F = 7/2 + 1/2 = 4; the other sub-level corresponds to anti-parallel electron and nuclear spin (i.e., pointing in opposite directions), leading to a total spin F = 7/2 − 1/2 = 3. In the caesium atom it so happens that the sub-level lowest in energy is the one with F = 3, while the F = 4 sub-level lies energetically slightly above. When the atom is irradiated with electromagnetic radiation having an energy corresponding to the energetic difference between the two sub-levels the radiation is absorbed and the atom is excited, going from the F = 3 sub-level to the F = 4 one. After a small fraction of a second the atom will re-emit the radiation and return to its F = 3 ground state. From the definition of the second it follows that the radiation in question has a frequency of exactly 9.19263177 GHz, corresponding to a wavelength of about 3.26 cm and therefore belonging to the microwave range.
See also[edit]
References[edit]
- ^L. Essen, J.V.L. Parry (1955). 'An Atomic Standard of Frequency and Time Interval: A Caesium Resonator'. Nature. 176 (4476): 280–282. Bibcode:1955Natur.176.280E. doi:10.1038/176280a0. S2CID4191481.
- ^Markowitz, W.; Hall, R.; Essen, L.; Parry, J. (1958). 'Frequency of Cesium in Terms of Ephemeris Time'. Physical Review Letters. 1 (3): 105. Bibcode:1958PhRvL..1.105M. doi:10.1103/PhysRevLett.1.105.
- ^'Comité international des poids et mesures (CIPM): Proceedings of the Sessions of the 86th Meeting'(PDF) (in French and English). Paris: Bureau International des Poids et Mesures. 23–25 Sep 1997. p. 229.
- ^'Resolution 1 of the 26th CGPM' (in French and English). Paris: Bureau International des Poids et Mesures. 2018. pp. 472 of the official French publication.
- This article incorporates public domain material from the General Services Administration document: 'Federal Standard 1037C'. (in support of MIL-STD-188)
External links[edit]
| Wikimedia Commons has media related to Caesium clocks. |
Cesium 133 Symbolic Notation
Cesium 133 Clock