Princeton's WordNet(0.00 / 0 votes)Rate this definition: geological time, geologic time(noun) the time of the physical formation and development of the earth (especially prior to human history)
Ionic radius, r ion, is the radius of an atom's ion.Although neither atoms nor ions have sharp boundaries, they are sometimes treated as if they were hard spheres with radii such that the sum of ionic radii of the cation and anion gives the distance between the ions in a crystal lattice.herefore, the distance between the Na + and Cl â ions is half of 564.02 pm, which is 282.01 pm. However, although X-ray crystallography gives the distance between ions, it doesn't indicate where the boundary is between those ions, so it doesn't directly give ionic radii.
(July 2017) The Bohr radius (a0 or rBohr) is a physical constant, approximately equal to the most probable distance between the center of a nuclide and the electron in a hydrogen atom in its ground state. It is named after Niels Bohr, due to its role in the Bohr model of an atom. Its value is 6989529177210670000â 5.2917721067(12)Ã10â11 m.[1][note 1]