Calcium atomic radius

Calcium has a cubic closest packed structure as a solid. Assuming that calcium has an atomic radius of 197 pm, calculate the density of solid calcium. 

Note Using the tabulated ionic radius of Ca (i.e. that of Ca2+) would be less valid than using the atomic radius of a neighboring monovalent ion, for the problem asks about a hypothetical compound of monovalent calcium. Predictions with the smaller Ca2+ radius (100 pm) differ substantially from those listed above the expected structure changes to rock-salt, the lattice enthalpy to 758 kJmol-1, Af// (CaCl) to —446kJ mol-1 and the final reaction enthalpy to +96 kJ mol-1. 

Calcium crystaUizes in a body-centered cubic structure, (a) How many Ca atoms are contained in each unit cell (b) How many nearest neighbors does each Ca atom possess (c) Estimate the length of the rmit cell edge, a, from the atomic radius of calcimn (1.97 A), (d) Estimate the density of Ca metal. 

Minasgeraisite-(Y) was described by Foord et al. (1986) as a new mineral from Minas Gerais, Brazil. X-ray powder diffraction data showed that the mineral is isostructural with gadolinite-(Y). However, minasgeraisite-(Y) has a peculiar chemical composition and includes significant amounts of Bi and Ca (Foord et al. 1986). It is unusual from the viewpoint of crystal chemistry that the calcium atom with a large ionic radius occupies the relatively small octahedral site which is occupied by Fe in the case of gadolinite-(Y). 

The radius of a calcium atom is only 0.000 000 019 7 cm, and its mass is 0.000000000000000000000 066 6 g. Later in this chapter, we will learn a better way to represent these numbers. 

Ofthe elements calcium, Ca, beryllium. Be, barium, Ba, and strontium, Sr, which has the largest atomic radius Explain your answer in terms of trends in the periodic table. 

This Group IIA (or Group 2) element (atomic symbol, Ca atomic number, 20 atomic weight, 40.078 electronic configuration = ls 2s 2p 3s 3p 4s ) loses both As electrons to form a divalent cation of 0.99A ionic radius. Ionic calcium combines readily with oxygen ligands (chiefly water, phosphates, polyphosphates, and carbox-ylates) to form stable metal ion complexes. Ca under-... 

Alkali-earth metals (calcium, barium, and magnesium) complex with polysaccharides extensively (Reisenhofer et al., 1984). Calcium has a smaller atomic and ionic radius than does sodium and, because it has two valence electrons, it is endowed with greater polarizing and bonding ability than Na+. Ca and Ca2+ easily form insoluble complexes with oxygenated compounds. Polysaccharide salts of alkali-earth metals are generally insoluble. 

The calcium, strontium, barium, and lead 80) complexes of 160 and 161 have also been reported. In these two ligands the six donor atoms are essentially confined in a plane these complexes thus permit study of unusual coordination geometries in species of high coordination number. Attempts to form alkali metal complexes with 160 and 161 under the same conditions as employed for the alkaline earth metal complexes have failed. The successful syntheses of complexes of the latter type indicate that the higher charge to radius ratio is of consequence when spherically charged cations are employed. Such metal ions have no apparent coordinative discrimination as the template ion 87). 

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