Experimental and calculated electron density distributions determined for oxide and silicate crystals and siloxane molecules provide a new basis for addressing the classic foundation of the crystal chemistry of silicates, including atomic/ionic radii, the radius ratio rule and the nexus between the Pauling's bond strength, resonance bond number, and bond length. The distributions indicate that the charge density of a bonded oxygen atom is highly distorted with its bonded radius decreasing systematically from 1.50 Å when bonded to highly electropositive atoms like sodium to ~0.65 Å when bonded to highly electronegative atoms like nitrogen. Rather than a single radius, the atom has as many bonded radii as it has bonded interactions. Bonded radii determined for the metal atoms match the Shannon effective ionic radii for the more electropositive atoms, but they depart and decrease systematically as the electronegativity of the M atoms increases. Pauling's first rule is considered to be irrelevant given the asphericity and the range of the bonded radii displayed by the O atom.
'%3e%3cpath fill='%23012169' d='M0 0v30h60V0z'/%3e%3cpath stroke='%23fff' stroke-width='6' d='m0 0 60 30m0-30L0 30'/%3e%3cpath stroke='%23C8102E' stroke-width='4' d='m0 0 60 30m0-30L0 30' clip-path='url(%23b)'/%3e%3cpath stroke='%23fff' stroke-width='10' d='M30 0v30M0 15h60'/%3e%3cpath stroke='%23C8102E' stroke-width='6' d='M30 0v30M0 15h60'/%3e%3c/g%3e%3c/svg%3e)