|
Ada Hitchins
Ada Florence Remfry Hitchins (26 June 1891 – 4 January 1972) was the principal research assistant of British chemist Frederick Soddy, who won the Nobel prize in 1921 for work on radioactive elements and the theory of isotopes. Hitchins isolated samples from uranium ores, taking precise and accurate measurements of atomic mass that provided the first experimental evidence for the existence of different isotopes. She also helped to discover the element protactinium, which Dmitri Mendeleev had predicted should occur in the periodic table between uranium and thorium. Education Ada Hitchins was born on 26 June 1891 in Tavistock, Devon, England, the daughter of William Hedley Hitchins, a supervisor of customs and excise, and his wife Annie Sarah Pearsons. The family lived for a time in Campbeltown, Scotland, where Hitchins attended high school, graduating in 1909. From there, she went to the University of Glasgow, obtaining her bachelor's degree in science, with honors, in 1913. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tavistock, Devon
Tavistock ( ) is an ancient stannary and market town within West Devon, England. It is situated on the River Tavy from which its name derives. At the 2011 census the three electoral wards (North, South and South West) had a population of 13,028. It traces its recorded history back to at least 961 when Tavistock Abbey, whose ruins lie in the centre of the town, was founded. Its most famous son is Sir Francis Drake. History Middle Ages The area around Tavistock (formerly Tavistoke), where the River Tavy runs wide and shallow allowing it to be easily crossed, and near the secure high ground of Dartmoor, was inhabited long before historical records. The surrounding area is littered with archaeological remains from the Bronze and Iron Ages and it is believed a hamlet existed on the site of the present town long before the town's official history began, with the founding of the Abbey. The abbey of Saint Mary and Saint Rumon was founded in 961 by Ordgar, Earl of Devon. After destruct ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tavistock
Tavistock ( ) is an ancient stannary and market town within West Devon, England. It is situated on the River Tavy from which its name derives. At the 2011 census the three electoral wards (North, South and South West) had a population of 13,028. It traces its recorded history back to at least 961 when Tavistock Abbey, whose ruins lie in the centre of the town, was founded. Its most famous son is Sir Francis Drake. History Middle Ages The area around Tavistock (formerly Tavistoke), where the River Tavy runs wide and shallow allowing it to be easily crossed, and near the secure high ground of Dartmoor, was inhabited long before historical records. The surrounding area is littered with archaeological remains from the Bronze Age, Bronze and Iron Ages and it is believed a Hamlet (place), hamlet existed on the site of the present town long before the town's official history began, with the founding of the Abbey. The abbey of Mary, the mother of Jesus, Saint Mary and Saint Rumon was ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Otto Hönigschmid
Otto Hönigschmid (13 March 1878 in Hořovice – 14 October 1945 in Munich) was a Czech/Austrian chemist. He published the first widely accepted experimental proof of isotopes along with Stefanie Horovitz. Throughout his career he worked to precisely define atomic weights for over 40 elements, and served on committees with the purpose of adopting internationally agreed upon values. After his home and laboratory in Munich were destroyed in World War II, he committed suicide in 1945. Education Hönigschmid studied organic chemistry at the Charles University in Prague under the guidance of Guido Goldschmiedt(the discoverer of the structure of papaverine). Additionally, he worked as a student researcher in Paris under Henri Moissan from 1904 to 1906. He was habilitated in 1908 upon publication of a thesis on carbide and silicide. Career and Scientific Research In 1909, Hönigschmid worked under Theodore Richards at Harvard University to determine the official weight of calcium. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Thorite
Thorite, (Th,U)SiO4, is a rare nesosilicate of thorium that crystallizes in the tetragonal system and is isomorphous with zircon and hafnon. It is the most common mineral of thorium and is nearly always strongly radioactive. It was named in 1829 to reflect its thorium content. Thorite was discovered in 1828 on the island of Løvøya, Norway, by the vicar and mineralogist, Hans Morten Thrane Esmark, who sent the first specimens of this black mineral to his father, Jens Esmark, who was a professor of mineralogy and geology. Occurrence Specimens of thorite generally come from igneous pegmatites and volcanic extrusive rocks, hydrothermal veins and contact metamorphic rocks. It is also known to occur as small grains in detrital sands. Crystals are rare, but when found can produce nicely shaped short prismatic crystals with pyramidal terminations. It is commonly associated with zircon, monazite, gadolinite, fergusonite, uraninite, yttrialite and pyrochlore. Thorite is currently an ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Half-life
Half-life (symbol ) is the time required for a quantity (of substance) to reduce to half of its initial value. The term is commonly used in nuclear physics to describe how quickly unstable atoms undergo radioactive decay or how long stable atoms survive. The term is also used more generally to characterize any type of exponential (or, rarely, non-exponential) decay. For example, the medical sciences refer to the biological half-life of drugs and other chemicals in the human body. The converse of half-life (in exponential growth) is doubling time. The original term, ''half-life period'', dating to Ernest Rutherford's discovery of the principle in 1907, was shortened to ''half-life'' in the early 1950s. Rutherford applied the principle of a radioactive element's half-life in studies of age determination of rocks by measuring the decay period of radium to lead-206. Half-life is constant over the lifetime of an exponentially decaying quantity, and it is a characteristic unit for ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Thorium-230
Thorium (90Th) has seven naturally occurring isotopes but none are stable. One isotope, 232Th, is ''relatively'' stable, with a half-life of 1.405×1010 years, considerably longer than the age of the Earth, and even slightly longer than the generally accepted age of the universe. This isotope makes up nearly all natural thorium, so thorium was considered to be mononuclidic. However, in 2013, IUPAC reclassified thorium as binuclidic, due to large amounts of 230Th in deep seawater. Thorium has a characteristic terrestrial isotopic composition and thus a standard atomic weight can be given. Thirty-one radioisotopes have been characterized, with the most stable being 232Th, 230Th with a half-life of 75,380 years, 229Th with a half-life of 7,917 years, and 228Th with a half-life of 1.92 years. All of the remaining radioactive isotopes have half-lives that are less than thirty days and the majority of these have half-lives that are less than ten minutes. One isotope, 229Th, has a nucl ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bertram Boltwood
Bertram Borden Boltwood (July 27, 1870 Amherst, Massachusetts – August 15, 1927, Hancock Point, Maine) was an American pioneer of radiochemistry. Boltwood attended Yale University, became a professor there and in 1910 was appointed chair of the first academic department of radiochemistry. He established that lead was the final decay product of uranium, noted that the lead-uranium ratio was greater in older rocks and, acting on a suggestion by Ernest Rutherford, was the first to measure the age of rocks by the decay of uranium to lead, in 1907. He got results of ages of 400 to 2200 million years, the first successful use of radioactive decay by Pb/U chemical dating. More recently, older mineral deposits have been dated to about 4.4 billion years old, close to the best estimate of the age of earth. His work with the uranium decay series led to the discovery of the parent of radium, a new element that he named ionium. Once the existence of isotopes was established, ion ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Radium
Radium is a chemical element with the symbol Ra and atomic number 88. It is the sixth element in group 2 of the periodic table, also known as the alkaline earth metals. Pure radium is silvery-white, but it readily reacts with nitrogen (rather than oxygen) upon exposure to air, forming a black surface layer of radium nitride (Ra3N2). All isotopes of radium are radioactive, the most stable isotope being radium-226 with a half-life of 1600 years. When radium decays, it emits ionizing radiation as a by-product, which can excite fluorescent chemicals and cause radioluminescence. Radium, in the form of radium chloride, was discovered by Marie and Pierre Curie in 1898 from ore mined at Jáchymov. They extracted the radium compound from uraninite and published the discovery at the French Academy of Sciences five days later. Radium was isolated in its metallic state by Marie Curie and André-Louis Debierne through the electrolysis of radium chloride in 1911. In nature, radium is found ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Chemical Elements
A chemical element is a species of atoms that have a given number of protons in their nuclei, including the pure substance consisting only of that species. Unlike chemical compounds, chemical elements cannot be broken down into simpler substances by any chemical reaction. The number of protons in the nucleus is the defining property of an element, and is referred to as its atomic number (represented by the symbol ''Z'') – all atoms with the same atomic number are atoms of the same element. Almost all of the baryonic matter of the universe is composed of chemical elements (among rare exceptions are neutron stars). When different elements undergo chemical reactions, atoms are rearranged into new compounds held together by chemical bonds. Only a minority of elements, such as silver and gold, are found uncombined as relatively pure native element minerals. Nearly all other naturally occurring elements occur in the Earth as compounds or mixtures. Air is primarily a mixture ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Uranium Ore Square
Uranium is a chemical element with the symbol U and atomic number 92. It is a silvery-grey metal in the actinide series of the periodic table. A uranium atom has 92 protons and 92 electrons, of which 6 are valence electrons. Uranium is weakly radioactive because all isotopes of uranium are unstable; the half-lives of its naturally occurring isotopes range between 159,200 years and 4.5 billion years. The most common isotopes in natural uranium are uranium-238 (which has 146 neutrons and accounts for over 99% of uranium on Earth) and uranium-235 (which has 143 neutrons). Uranium has the highest atomic weight of the primordially occurring elements. Its density is about 70% higher than that of lead, and slightly lower than that of gold or tungsten. It occurs naturally in low concentrations of a few parts per million in soil, rock and water, and is commercially extracted from uranium-bearing minerals such as uraninite. In nature, uranium is found as uranium-238 (99.2739–99. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Kenya
) , national_anthem = "Ee Mungu Nguvu Yetu"() , image_map = , map_caption = , image_map2 = , capital = Nairobi , coordinates = , largest_city = Nairobi , official_languages = Constitution (2009) Art. 7 ational, official and other languages"(1) The national language of the Republic is Swahili. (2) The official languages of the Republic are Swahili and English. (3) The State shall–-–- (a) promote and protect the diversity of language of the people of Kenya; and (b) promote the development and use of indigenous languages, Kenyan Sign language, Braille and other communication formats and technologies accessible to persons with disabilities." , languages_type = National language , languages = Swahili , ethnic_groups = , ethnic_groups_year = 2019 census , religion = , religion_year = 2019 census , demonym = ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
.svg "Click for more on -> Radium")
%2C_black_and_white.png "Click for more on -> Chemical Elements")
