Chemistry (Mixed Test)

Allred and Rochow considered that electronegativity should be related to the charge experienced by an electron on the surface of an atom. The higher the charge per unit area of atomic surface, the greater the tendency of that atom to attract electrons. The effective nuclear charge, Z* experienced by valence electrons can be estimated using Slater's rules.

The halogens are five non-metallic elements found in group 17 of the periodic table. The term halogen means salt-former and compounds containing halogens are called salts. All halogens have 7 electrons in their outer shells, giving them an oxidation number of -1. The halogens exist, at room temperature, in all three states of matter:

Lonsdaleite is a hexagonal allotrope of the carbon allotrope diamond, believed to form from graphite present in meteorites upon their impact to Earth. The great heat and stress of the impact transforms the graphite into diamond, but retains graphite's hexagonal crystal lattice.

Prismane C₈ is a theoretically predicted metastable carbon allotrope comprising an atomic cluster of eight carbon atoms, with the shape of an elongated triangular bipyramid- a six-atom triangular prism with two more atoms above and below its bases.

Noble metals are metals that are resistant to corrosion and oxidation in moist air, unlike most base metals.They tend to be precious, often due to their rarity in the earth's crust. The noble metals are considered to be (in order of increasing atomic number) ruthenium, rhodium, palladium, silver, osmium, iridium, platinum, and gold.

The s-block of the periodic table of elements consists of the first two groups: the alkali metals and alkaline earth metals, plus hydrogen and helium.These elements are distinguished by the property that in the atomic ground state, the highest energy electron is in a s-orbital. Except in hydrogen and helium, these electrons are very easily lost to form positive ions.

A fullerene is any molecule composed entirely of carbon, in the form of a hollow sphere, ellipsoid, or tube. Spherical fullerenes are also called buckyballs, and they resemble the balls used in association football. Cylindrical ones are called carbon nanotubes or buckytubes.

The muon is an elementary particle similar to the electron, with a unitary negative electric charge and a spin of 1/2. Together with the electron, the tau, and the three neutrinos, it is classified as a lepton.

The up quark or u quark (from its symbol, u) is the lightest of all quarks, a type of elementary particle, and a major constituent of matter. It, along with the down quark, forms the neutrons (one up quark, two down quarks) and protons (two up quarks, one down quark) of atomic nuclei.

The platinum group metals is a term used sometimes to collectively refer to six metallic elements clustered together in the periodic table. These elements are all transition metals.The platinum metals have outstanding catalytic properties. They are highly resistant to wear and tarnish, making platinum, in particular, well suited for fine jewellery. Other distinctive properties include resistance to chemical attack, excellent high-temperature characteristics, and stable electrical properties.

Mesons are subatomic particles composed of one quark and one antiquark, bound together by the strong interaction. Because mesons are composed of sub-particles, they have a physical size, with a radius roughly one femtometer: 10-15 m, which is about 2⁄3 the size of a proton or neutron.

Singlet oxygen is the common name used for the diamagnetic form of molecular oxygen which is less stable than the normal triplet oxygen. Because of its unusual properties, singlet oxygen can persist for over an hour at room temperature, depending on the environment.

Part of the cooling system where the primary coolant bringing heat from the reactor is used to make steam for the turbine. Reactors may have up to four loops, each with a steam generator. It is not a component of Boiling Water Reactor (BWR).

Acicular ferrite is a microstructure of ferrite that is characterised by needle shaped crystallites or grains when viewed in two dimensions. The grains, actually three dimensional in shape, have a thin lenticular shape. This microstructure is advantageous over other microstructures because of its chaotic ordering, which increases toughness.

A homogeneous mixture has the same uniform appearance and composition throughout. Many homogeneous mixtures are commonly referred to as solutions.

Black phosphorus is the thermodynamically stable form of phosphorus at room temperature and pressure. It is obtained by heating white phosphorus under high pressures (12,000 atmospheres). In appearance, properties and structure it is very like graphite, being black and flaky, a conductor of electricity, and having puckered sheets of linked atoms.

These are the second generation of British gas-cooled reactors, using graphite moderator and carbon dioxide as coolant. The fuel is uranium oxide pellets, enriched to 2.5-3.5%, in stainless steel tubes. The carbon dioxide circulates through the core, reaching 650°C and then past steam generator tubes outside it, but still inside the concrete and steel pressure vessel. Control rods penetrate the moderator and a secondary shutdown system involves injecting nitrogen to the coolant.

Carbon nanobuds are a newly discovered allotrope of carbon in which fullerene like buds are covalently attached to the outer sidewalls of the carbon nanotubes. This hybrid material has useful properties of both fullerenes and carbon nanotubes. For instance, they have been found to be exceptionally good field emitters.

α-rhombohedral boron has a unit cell of twelve boron atoms. The structure consists of B12 icosahedra in which each boron atom has five nearest neighbors within the icosahedron. If the bonding were the conventional covalent type then each boron would have donated 5 electrons.

Activated carbon, also called activated charcoal, activated coal or carbo activatus, is a form of carbon that has been processed to make it extremely porous and thus to have a very large surface area available for adsorption or chemical reactions.

Carbon fiber alternatively graphite fiber, carbon graphite or CF, is a material consisting of extremely thin fibers about 5-10 μm in diameter and composed mostly of carbon atoms. The carbon atoms are bonded together in microscopic crystals that are more or less aligned parallel to the long axis of the fiber.

The nuclear reactor core is the region with in a nuclear reactor where the nuclear fuel assemblies are located and the nuclear reaction consequently takes place. The core of the reactor contains all the nuclear fuels and generates all of the heat. It contains low-enriched uranium, controls systems and structural materials.The core contain hundreds of thousands of individual fuel pins.

Thermal reactors use slowed or thermal neutrons. Almost all current reactors are of this type. These contain neutron moderator materials that slow neutrons until their neutron temperature is thermalised, that is, until their kinetic energy approaches the average kinetic energy of the surrounding particles.

Hypochlorous acid is a weak acid with the chemical formula HClO. It forms when chlorine dissolves in water. It cannot be isolated in pure form due to rapid equilibration with its precursor. HClO is an oxidizer, and as its sodium salt; sodium hypochlorite, (NaClO), or its calcium salt calcium hypochlorite, is used as a bleach, a deodorant, and a disinfectant.

The electron affinity of a molecule or atom is the energy change when an electron is added to the neutral atom to form a negative ion. This property can only be measured in an atom in gaseous state.