Which metal is first in the third row of the d block, lanthanum or lutetium?

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Offline chiralSPO

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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?
« Last Edit: 01/07/2016 07:36:33 by chris »


Offline Marius Quod

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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.