A Consistent Approach toward Atomic Radii

Hybrid-density functional calculations on methyl group substituted elemental hydrides of the form H 3 C−EH n (E is any main block or d block transition element and n is 0, 1, 2, 3, or 4 depending on the position of E in the periodic table) give atomic radii (R A ) as the C−E bond distance minus half of the C−C bond distance of ethane. R A values show good linear correlations with the experimental covalent radii, Slater's empirical set of atomic radii, and experimental carbon-based atomic radii particularly for the main block elements. Except a few cases, the sum of any two R A values reproduces very well the corresponding mean single bond distances in molecules. Further, R A values provide the calculation of an expected density (Ds‘) of the element, which shows a good linear correlation with solid-state density of elements (Ds) when they are metals, suggesting similarity in their atomic packing. The percentage of free space ( V free ) in the solid-state calculated using Ds‘ and Ds suggests that all the metals have V free below 66, all the metalloids have V free between 66 and 71, and all the nonmetals have V free above 71.