Ionic radius halogens

The pentahalides of phosphorus, PX, in the gas phase exhibit varying tendencies to dissociate into trihaUde and halogen. InstabiUty increases with increasing ionic radius of the halogen. The pentafluoride appears to be thermally stable. Dissociation of the pentachloride, a few percent at 100°C and 101.3 kPa (1 atm), is essentially completed at 300°C (36). The pentabromide is partially dissociated in the Hquid state and totally dissociated above ca 35°C (39). Pentaiodide does not exist. The molecules of PF and PCl in the vapor phase are trigonal bipyramids. In the crystalline state, both pentachloride and pentabromide have ionic stmctures, ie, [PClJ IPClg] and [PBr4]" PBrJ , respectively. The PX" 4 cations are tetrahedral and the PX anion is octahedral (36,37). 

M +(g)-(-e" this is 7297kJ mol for Li but drops to 2255kJmol for Cs. The largest possible lattice energy to compensate for this would be obtained with the smallest halogen F and (making plausible assumptions on lattice structure and ionic radius) calculations indicate that CsF2 could indeed be formed exothermically from its elements ... 

Each rubidium halide (Group VIIA element) crystallizing in the NaCl-type lattice has a unit cell length 30 pm greater than that for the corresponding potassium salt of the same halogen. What is the ionic radius of Rb+ computed from these data ... 

In Table 1.1 we have collected some atomic and nuclear properties of the halogens, fluorine being included for completeness and comparison. To stress the ambiguity of some properties such as electronegativity and ionic radius we have listed values from different authors - the original articles should be consulted for an account of the underlying criteria and definitions. 

A an increase in atomic radius B an increase in ionization energy and hence decrease in reactivity C a decrease in ionic radius D an increase in electronegativity Q15 Which of the following properties of the halogens increase from F to I ... 

Metallic, covalent, and ionic radii of americium in various oxidation states were first calculated by Zachariasen [73] (see Section 20.7 and Table 20.8). The radius of americium metal (coordination number (CN) 12) is 1.73 A [74]. On the basis of a refined crystal structure for AmCls, Bums and Peterson [75] calculated the ionic radius (CN 6) of Am in AmCls to be 0.984 0.003 A. It is beneficial to introduce the summary bond length-bond strength formulas of Zachariasen [76] at this point. They provide, as a function of americium valence and coordination number, a condensation of the many ameiidum-oxygen and ameiidum-halogen... 

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