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Properties and applications of engineering materials
Published in Alan Darbyshire, Charles Gibson, Mechanical Engineering, 2023
Alan Darbyshire, Charles Gibson
There are 92 naturally occurring chemical elements. A chemical element cannot be split into other substances. It is made up of atoms that are all the same. Sometimes, groups of two or more atoms combine together to form molecules. These too are identical in a pure element. Atoms are made up of particles. The heaviest of these are protons and neutrons which are roughly the same size and form the central core, or nucleus, of an atom.
Petroleum Pre-Period
Published in Muhammad Abdul Quddus, Petroleum Science and Technology, 2021
A chemical element is a substance that cannot be broken into a smaller chemical substance, except in a nuclear reaction. The element is the simplest form of matter; the elements are produced by bonding among atoms of the same types. About 115 elements exist in the universe. Eighty-three elements occur naturally, and the rest are produced by artificial nuclear reaction. A nuclear reaction differs from a chemical reaction. A chemical reaction is the sharing of outer orbital electrons of the reactant atoms. The nucleus of the atom remains intact in a chemical reaction. Nuclear reactions are the fusion (combination) or fission (disintegration) of atomic nuclei. The change in nucleus composition (neutron and proton) generates new atoms with the release of large amounts of radiation. The fission reaction produces lower atomic mass atoms and fusion generates heavier atomic mass atoms. All nuclear reactions are exothermic, whereas chemical reactions are exothermic or endothermic.
Introduction to Nanosensors
Published in Vinod Kumar Khanna, Nanosensors, 2021
The Periodic Table is a compilation of the chemical elements in ascending order of their atomic numbers to show the similarities of properties of elements. The vertical columns of the periodic table numbered I–VIII are called groups, while the horizontal rows 1–7 are known as periods. The groups contain elements that are similar to each other.
Characterization of sulphur particles: prills vs. granules
Published in Particulate Science and Technology, 2022
Faisal Momoniat, Nejat Rahmanian
Sulfur is the tenth most common element by mass in the universe and the fifth most common on planet earth. It has been known as brimstone in ancient times. Sulfur is a chemical element with the chalcogenide atomic number. It is a pale yellow, nonmetallic solid which can be found as a pure element or within sulfide and sulfate minerals. An essential element for life and found in two amino acids, cysteine and methionine, Greenwood and Earnshaw (1997). Sulfur can take up many compound forms as shown in Table 1. The global processing capacity annually stands at sixty-eight million tonnes, Markit (2019). Most elemental sulfur is produced nowadays as a by-product from petrochemical industries and natural gas. However, sulfur is being increasingly used in agriculture to manufacturing fertilizers such as ammonium sulfate and phosphates. Urea has also been trialed and used efficiently within this industry as reported by, Smil (2001).
On the structural and thermophysical study of Pb-doped Se-Te-In nanochalcogenide alloys
Published in Journal of Asian Ceramic Societies, 2020
Balbir Singh Patial, Nagesh Thakur
The average heat of atomization () is a parameter that reflects relative bond strength of a material as it directly provides a measure of cohesive energy. It represents a heat change in a chemical substance by total separation of all atoms (either a chemical element or a chemical compound) [44]. Thus, assets of chalcogenide system must be correlated with . Pauling stated that [68] for binary semiconductor consist of A along with B atoms, at standard pressure as well as temperature, the is the sum of heat of formation (ΔH) with average heats of atomization and , respectively, that related to the average nonpolar-bond energy of the two atoms:
Technetium-99m metastable radiochemistry for pharmaceutical applications: old chemistry for new products
Published in Journal of Coordination Chemistry, 2019
Bianca Costa, Derya Ilem-Özdemir, Ralph Santos-Oliveira
The chemical element technetium whose symbol is Tc has atomic number 43 and is located in group 7 (7B) of the periodic table. All isotopes of technetium are radioactive. The two most prevalent isotopes are 99mTc formed from the decay of 99Mo and 99Tc, the decay product of 99mTc. 99Tc (βmax: 274 keV) is a significant by-product of U-235 fission (6% thermal neutron yield). With a half-life of 2.1 × 105 years, 99Tc can build up in the environment and can be obtained in macroscopic quantities. In the metallic form, 99Tc is a transition metal, silvery gray. Like the other transition metals, 99Tc presents peculiar properties, such as varied colors, various oxidation numbers and different coordination numbers, which result from the existence of a sub-level “d” partially filled in the valence layer [11].