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Earth radius (denoted as R 🜨 or R E) is the distance from the center of Earth to a point on or near its surface. Approximating the figure of Earth by an Earth spheroid (an oblate ellipsoid), the radius ranges from a maximum (equatorial radius, denoted a) of nearly 6,378 km (3,963 mi) to a minimum (polar radius, denoted b) of nearly 6,357 km (3,950 mi).
The mean radius in astronomy is a measure for the size of planets and small Solar System bodies. Alternatively, the closely related mean diameter ( D {\displaystyle D} ), which is twice the mean radius, is also used.
A replica of an apparatus used by Geiger and Marsden to measure alpha particle scattering in a 1913 experiment. The Rutherford scattering experiments were a landmark series of experiments by which scientists learned that every atom has a nucleus where all of its positive charge and most of its mass is concentrated.
Accessible surface area is often used when calculating the transfer free energy required to move a biomolecule from an aqueous solvent to a non-polar solvent, such as a lipid environment. The LCPO method is also used when calculating implicit solvent effects in the molecular dynamics software package AMBER.
For more recent data on covalent radii see Covalent radius. Just as atomic units are given in terms of the atomic mass unit (approximately the proton mass), the physically appropriate unit of length here is the Bohr radius, which is the radius of a hydrogen atom. The Bohr radius is consequently known as the "atomic unit of length".
The concept of atomic radius was preceded in the 19th century by the concept of atomic volume, a relative measure of how much space would on average an atom occupy in a given solid or liquid material. [3] By the end of the century this term was also used in an absolute sense, as a molar volume divided by Avogadro constant. [4]
For typical ionic solids, the cations are smaller than the anions, and each cation is surrounded by coordinated anions which form a polyhedron.The sum of the ionic radii determines the cation-anion distance, while the cation-anion radius ratio + / (or /) determines the coordination number (C.N.) of the cation, as well as the shape of the coordinated polyhedron of anions.
A research proposal is a document proposing a research project, generally in the sciences or academia, and generally constitutes a request for sponsorship of that research. [1] Proposals are evaluated on the cost and potential impact of the proposed research, and on the soundness of the proposed plan for carrying it out. [ 2 ]