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R. J. Gillespie
Ronald James Gillespie, (August 21, 1924 – February 26, 2021) was a British chemist specializing in the field of molecular geometry, who arrived in Canada after accepting an offer that included his own laboratory with new equipment, which post-World War II Britain could not provide. He was responsible for establishing inorganic chemistry education in Canada. He was educated at the University of London obtaining a B.Sc. in 1945, a Ph.D. in 1949 and a D.Sc. in 1957. He was assistant lecturer and then lecturer in the Department of Chemistry at University College London in England from 1950 to 1958. He moved to McMaster University, Hamilton, Ontario, Canada in 1958, passing away on February 26, 2021 at the age of ninety-six years in the nearby town of Dundas, Ontario. He was elected as a Fellow of the Royal Society of Canada in 1965, a Fellow of the Royal Society of London in 1977, and made a member of the Order of Canada in 2007. Gillespie did extensive work on expanding the ide ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dundas, Ontario
: ''For the county in eastern Ontario see Dundas County, Ontario. For the upper tier county, see United Counties of Stormont, Dundas and Glengarry.'' Dundas is a community and town in Hamilton, Ontario, Canada. It is nicknamed the ''Valley Town'' because of its topographical location at the bottom of the Niagara Escarpment on the western edge of Lake Ontario. The population has been stable for decades at about twenty thousand, largely because it has not annexed rural land from the protected Dundas Valley Conservation Area. Notable events are the Buskerfest in early June, and the Dundas Cactus Festival in August. History and politics First Nations peoples have inhabited the Dundas area for as much as 10,000 years. The first European to visit the area was Etienne Brulé in 1616, who noted that about 40,000 "Neutrals" lived in the Burlington Bay area. History and politics to 1974 The location of Dundas was a prime location for hunting wildfowl, hence a "hunter's paradise" and w ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Chemist
A chemist (from Greek ''chēm(ía)'' alchemy; replacing ''chymist'' from Medieval Latin ''alchemist'') is a scientist trained in the study of chemistry. Chemists study the composition of matter and its properties. Chemists carefully describe the properties they study in terms of quantities, with detail on the level of molecules and their component atoms. Chemists carefully measure substance proportions, chemical reaction rates, and other chemical properties. In Commonwealth English, pharmacists are often called chemists. Chemists use their knowledge to learn the composition and properties of unfamiliar substances, as well as to reproduce and synthesize large quantities of useful naturally occurring substances and create new artificial substances and useful processes. Chemists may specialize in any number of subdisciplines of chemistry. Materials scientists and metallurgists share much of the same education and skills with chemists. The work of chemists is often related to the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Atomic Radius
The atomic radius of a chemical element is a measure of the size of its atom, usually the mean or typical distance from the center of the nucleus to the outermost isolated electron. Since the boundary is not a well-defined physical entity, there are various non-equivalent definitions of atomic radius. Four widely used definitions of atomic radius are: Van der Waals radius, ionic radius, metallic radius and covalent radius. Typically, because of the difficulty to isolate atoms in order to measure their radii separately, atomic radius is measured in a chemically bonded state; however theoretical calculations are simpler when considering atoms in isolation. The dependencies on environment, probe, and state lead to a multiplicity of definitions. Depending on the definition, the term may apply to atoms in condensed matter, covalently bonding in molecules, or in ionized and excited states; and its value may be obtained through experimental measurements, or computed from theoretical ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Electronegativity
Electronegativity, symbolized as , is the tendency for an atom of a given chemical element to attract shared electrons (or electron density) when forming a chemical bond. An atom's electronegativity is affected by both its atomic number and the distance at which its valence electrons reside from the charged nucleus. The higher the associated electronegativity, the more an atom or a substituent group attracts electrons. Electronegativity serves as a simple way to quantitatively estimate the bond energy, and the sign and magnitude of a bond's chemical polarity, which characterizes a bond along the continuous scale from covalent to ionic bonding. The loosely defined term electropositivity is the opposite of electronegativity: it characterizes an element's tendency to donate valence electrons. On the most basic level, electronegativity is determined by factors like the nuclear charge (the more protons an atom has, the more "pull" it will have on electrons) and the number and location ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fluorine
Fluorine is a chemical element with the symbol F and atomic number 9. It is the lightest halogen and exists at standard conditions as a highly toxic, pale yellow diatomic gas. As the most electronegative reactive element, it is extremely reactive, as it reacts with all other elements except for the light inert gases. Among the elements, fluorine ranks 24th in universal abundance and 13th in terrestrial abundance. Fluorite, the primary mineral source of fluorine which gave the element its name, was first described in 1529; as it was added to metal ores to lower their melting points for smelting, the Latin verb meaning 'flow' gave the mineral its name. Proposed as an element in 1810, fluorine proved difficult and dangerous to separate from its compounds, and several early experimenters died or sustained injuries from their attempts. Only in 1886 did French chemist Henri Moissan isolate elemental fluorine using low-temperature electrolysis, a process still employed for modern pr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Covalent Radius
The covalent radius, ''r''cov, is a measure of the size of an atom that forms part of one covalent bond. It is usually measured either in picometres (pm) or angstroms (Å), with 1 Å = 100 pm. In principle, the sum of the two covalent radii should equal the covalent bond length between two atoms, ''R''(AB) = ''r''(A) + ''r''(B). Moreover, different radii can be introduced for single, double and triple bonds (r1, r2 and r3 below), in a purely operational sense. These relationships are certainly not exact because the size of an atom is not constant but depends on its chemical environment. For heteroatomic A–B bonds, ionic terms may enter. Often the polar covalent bonds are shorter than would be expected based on the sum of covalent radii. Tabulated values of covalent radii are either average or idealized values, which nevertheless show a certain transferability between different situations, which makes them useful. The bond lengths ''R''(AB) are measured by X-ray ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Covalent Radius Of Fluorine
The covalent radius of fluorine is a measure of the size of a fluorine atom; it is approximated at about 60 picometres. Since fluorine is a relatively small atom with a large electronegativity, its covalent radius is difficult to evaluate. The covalent radius is defined as half the bond lengths between two neutral atoms of the same kind connected with a single bond. By this definition, the covalent radius of F is 71 pm. However, the F-F bond in F2 is abnormally weak and long. Besides, almost all bonds to fluorine are highly polar because of its large electronegativity, so the use of a covalent radius to predict the length of such a bond is inadequate and the bond lengths calculated from these radii are almost always longer than the experimental values. Bonds to fluorine have considerable ionic character, a result of its small atomic radius and large electronegativity. Therefore, the bond length of F is influenced by its ionic radius, the size of ions in an ionic crystal, whi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
LCP Theory
In chemistry, ligand close packing theory (LCP theory), sometimes called the ligand close packing model describes how ligand – ligand repulsions affect the geometry around a central atom.''Teaching the VSEPR model and electron densities'' R. J. Gillespie and C. F. Matta, Chem. Educ. Res. Pract. Eur.: 2001, 2, 73-90 It has been developed by R. J. Gillespie and others from 1997 onwards Reinterpretation of the Lengths of Bonds to Fluorine in Terms of an Almost Ionic Model E A. Robinson , S A. Johnson, Ting-Hua Tang, and R J. Gillespie Inorg. Chem., 36 (14), 3022 -3030, 1997. ic961315b S0020-1669(96)01315-8 and is said to sit alongside VSEPR which was originally developed by R. J. Gillespie and R Nyholm.''Inorganic stereochemistry'' Gillespie, R.J. & Nyholm, R.S. (1957). Quarterly Reviews of the Chemical Society, 11, 339-380 The inter-ligand distances in a wide range of molecules have been determined. The example below shows a series of related molecules:''Bonding and Geometry of ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Chemistry
Chemistry is the science, scientific study of the properties and behavior of matter. It is a natural science that covers the Chemical element, elements that make up matter to the chemical compound, compounds made of atoms, molecules and ions: their composition, structure, properties, behavior and the changes they undergo during a Chemical reaction, reaction with other Chemical substance, substances. Chemistry also addresses the nature of chemical bonds in chemical compounds. In the scope of its subject, chemistry occupies an intermediate position between physics and biology. It is sometimes called the central science because it provides a foundation for understanding both Basic research, basic and Applied science, applied scientific disciplines at a fundamental level. For example, chemistry explains aspects of plant growth (botany), the formation of igneous rocks (geology), how atmospheric ozone is formed and how environmental pollutants are degraded (ecology), the properties ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ronald Sydney Nyholm
Sir Ronald Sydney Nyholm (29 January 1917 – 4 December 1971) was an Australian chemist who was a leading figure in inorganic chemistry in the 1950s and 1960s. Education Born on 29 January 1917 as the fourth in a family of six children. Nyholm's father, Eric Edward Nyholm (1878–1932) was a railway guard. Nyholm's paternal grandfather, Erik Nyholm (1850–1887) was a coppersmith born in Nykarleby in the Swedish-speaking part of Finland, who migrated to Adelaide in 1873. Ronald Nyholm valued his Finnish roots and was particularly proud in his election in 1959 as Corresponding Member of the Finnish Chemical Society. Hailing from the small mining town of Broken Hill, New South Wales, he was early exposed to the role of inorganic chemistry. He attended Burke Ward Public School and Broken Hill High School. Nyholm married Maureen Richardson of Epping, a suburb of Sydney, NSW, at the parish church in Kensington, London on 6 August 1948. After graduating from Broken Hill High ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
VSEPR
Valence shell electron pair repulsion (VSEPR) theory ( , ), is a model used in chemistry to predict the geometry of individual molecules from the number of electron pairs surrounding their central atoms. It is also named the Gillespie-Nyholm theory after its two main developers, Ronald Gillespie and Ronald Nyholm. The premise of VSEPR is that the valence electron pairs surrounding an atom tend to repel each other and will, therefore, adopt an arrangement that minimizes this repulsion. This in turn decreases the molecule's energy and increases its stability, which determines the molecular geometry. Gillespie has emphasized that the electron-electron repulsion due to the Pauli exclusion principle is more important in determining molecular geometry than the electrostatic repulsion. The insights of VSEPR theory are derived from topological analysis of the electron density of molecules. Such quantum chemical topology (QCT) methods include the electron localization function (ELF) and ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Royal Society Of Canada
The Royal Society of Canada (RSC; french: Société royale du Canada, SRC), also known as the Academies of Arts, Humanities and Sciences of Canada (French: ''Académies des arts, des lettres et des sciences du Canada''), is the senior national, bilingual council of distinguished Canadian scholars, humanists, scientists and artists. The primary objective of the RSC is to promote learning and research in the arts, the humanities and the sciences. The RSC is Canada's National Academy and exists to promote Canadian research and scholarly accomplishment in both official languages, to recognize academic and artistic excellence, and to advise governments, non-governmental organizations and Canadians on matters of public interest. History In the late 1870s, the Governor General of Canada, the Marquis of Lorne, determined that Canada required a cultural institution to promote national scientific research and development. Since that time, succeeding Governor Generals have remained involved w ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
