Naked Science Forum
Non Life Sciences => Chemistry => Topic started by: chiralSPO on 01/07/2016 02:19:56
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Which metal is the first member of the third row of the "d block"? Some periodic tables show lutetium (Z = 71) , some show lanthanum (Z= 57). Some show all of the "lanthanides" together...
Lu : https://www.google.com/url?sa=i&rct=j&q=&esrc=s&source=images&cd=&cad=rja&uact=8&ved=0ahUKEwit8qjXidHNAhWDph4KHcPvAscQjRwIBw&url=https%3A%2F%2Fen.wikipedia.org%2Fwiki%2FPeriodic_table&psig=AFQjCNFJT3yT9JJOMNPpyatKTjKasXLJYA&ust=1467421615621145
La: https://www.google.com/url?sa=i&rct=j&q=&esrc=s&source=images&cd=&cad=rja&uact=8&ved=0ahUKEwj58r-EitHNAhWDXR4KHSYGCfsQjRwIBw&url=http%3A%2F%2Foxford-labs.com%2Fx-ray-fluorescence%2Fthe-periodic-table%2F&psig=AFQjCNFJT3yT9JJOMNPpyatKTjKasXLJYA&ust=1467421615621145]https://www.google.com/url?sa=i&rct=j&q=&esrc=s&source=images&cd=&cad=rja&uact=8&ved=0ahUKEwj58r-EitHNAhWDXR4KHSYGCfsQjRwIBw&url=http%3A%2F%2Foxford-labs.com%2Fx-ray-fluorescence%2Fthe-periodic-table%2F&psig=AFQjCNFJT3yT9JJOMNPpyatKTjKasXLJYA&ust=1467421615621145
Unspecified: https://www.google.com/url?sa=i&rct=j&q=&esrc=s&source=images&cd=&cad=rja&uact=8&ved=0ahUKEwjclrTpidHNAhUJph4KHfnBCUMQjRwIBw&url=http%3A%2F%2Fsciencenotes.org%2Fprintable-periodic-table%2F&psig=AFQjCNFJT3yT9JJOMNPpyatKTjKasXLJYA&ust=1467421615621145
If we go by physical/chemical properties of scandium and yttrium, like density and ionization energy Lu makes more sense as the first d-metal, and it would make sense given the previous structure of the periodic table, that the first d metals would align with the last of the f-block, not the first... So why does anyone do put La in instead?
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La is shown as the first element in the third row of the d block simply because it's the first element in period 6 to have a d electron. As to physical and chemical properties, the density of Ba (in group 2) is about the average of the density of Cs (in group 1) and that of La (in group 3). An analogous density relationship is seen in period 5 for Rb-Sr-Y, and in period 4 for K-Ca-Sc. OTOH, the difference in the ionisation energy of La, at 5.58 eV, and that of Lu, at 5.426 eV, seems to be too small to draw any meaning from.