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Does it tell us anything we didn't know, doesn't appear to. 1. Have a look at the heading under "Gruppe." It's the formula of the element's oxide. That hasn't

by apo 8y ago

Does it tell us anything we didn't know, doesn't appear to. 1. Have a look at the heading under "Gruppe." It's the formula of the element's oxide. That hasn't shown up on periodic tables for a long time. It implies that determining the oxide formula may have been tricky for students of the time. Today students are taught how to make any formula (not just oxides) given the group number of the component elements. 2. Mendeleev's name is explicitly mentioned. You also won't find that on any modern periodic tables. 3. The transition metals are not segregated but lumped into main groups. Today they're separated into ten groups of their own, but the rare earths and transuranium elements are kind of lumped together with no groups of their own.

jcranmer 8y ago
GP's point is that this artifact doesn't introduce a new variant of periodic table that was unknown to historians. Hell, Wikipedia has had a virtually similar table listed in its history of the periodic table for close to 4 years now. > 3. The transition metals are not segregated but lumped into main groups. Today they're separated into ten groups of their own, but the rare earths and transuranium elements are kind of lumped together with no groups of their own. The only known f-block elements known at the time were lanthanum [1], cerium, thorium, uranium, and erbium. Plus didymium, which is actually a mixture of praseodymium and neodymium that was thought to be an element. On the base of atomic mass, there was clearly a large slug of missing elements, so the assumption was that when the d-block returns to hafnium, there must have been missing elements to fill in the expected rows. The modern periodic table is centered essentially on electronic configuration. The standard table has the s-block on the left, the p-block on the right, the d-block in the middle, and the f-block below the table, vaguely indicated as appearing either immediately after the s-block or after the first element in the d-block. Elements are sorted into these blocks based on which orbital the last electron filters into, although by the time you hit the f-block, the nominal rule implied by the periodic table has lots of exceptions. But this table predates the discovery of atomic orbital theory. It even predates the notion of atomic number--the elements are listed with their atomic mass. The group numbers that you see used to be common in chemistry, although often addended with A or B (where CAS said that the d-block groups were all suffixed with B and the others with A; and IUPAC said that the first half of columns were A and the second half were B). [1] Sidestepping the entire debate here about whether lanthanum and actinium are d-block elements, or lutetium and lawrencium are.
quietbritishjim 8y ago
> Have a look at the heading under "Gruppe." It's the formula of the element's oxide. According to the Periodic Videos video (linked from another comment), the reason those are there is to justify splitting the list of elements into rows in those particular places. The reasoning today is to do with eletron shells (I'm not a chemist but I presume that electron shells are also the root cause of those formulae) but at the time periodic table was created electrons hadn't yet been discovered!
- apo 8y ago
  You are right (slaps forehead), and I was not thinking about the historical context. The earliest tables were based on "valence", or the ratio with which an element tended to combine with other elements in compounds. Two of the most consistent and easily obtained compounds are those of hydrogen and oxygen, which nearly always combine with other "monovalent" elements in ratios of 1 and 2, respectively. When a new element was discovered, the ratios with which it formed oxides and hydrides could be determined, and this would allow its placement on the table. A student from the late 1800s would only be able to think in terms of equivalents, not electrons and their orbitals - as you point out. The inclusion of hydride and oxide formula templates would have been an integral part of using the table.

by apo 8y ago

jcranmer 8y ago

GP's point is that this artifact doesn't introduce a new variant of periodic table that was unknown to historians. Hell, Wikipedia has had a virtually similar table listed in its history of the periodic table for close to 4 years now. > 3. The transition metals are not segregated but lumped into main groups. Today they're separated into ten groups of their own, but the rare earths and transuranium elements are kind of lumped together with no groups of their own. The only known f-block elements known at the time were lanthanum [1], cerium, thorium, uranium, and erbium. Plus didymium, which is actually a mixture of praseodymium and neodymium that was thought to be an element. On the base of atomic mass, there was clearly a large slug of missing elements, so the assumption was that when the d-block returns to hafnium, there must have been missing elements to fill in the expected rows. The modern periodic table is centered essentially on electronic configuration. The standard table has the s-block on the left, the p-block on the right, the d-block in the middle, and the f-block below the table, vaguely indicated as appearing either immediately after the s-block or after the first element in the d-block. Elements are sorted into these blocks based on which orbital the last electron filters into, although by the time you hit the f-block, the nominal rule implied by the periodic table has lots of exceptions. But this table predates the discovery of atomic orbital theory. It even predates the notion of atomic number--the elements are listed with their atomic mass. The group numbers that you see used to be common in chemistry, although often addended with A or B (where CAS said that the d-block groups were all suffixed with B and the others with A; and IUPAC said that the first half of columns were A and the second half were B). [1] Sidestepping the entire debate here about whether lanthanum and actinium are d-block elements, or lutetium and lawrencium are.

quietbritishjim 8y ago

> Have a look at the heading under "Gruppe." It's the formula of the element's oxide. According to the Periodic Videos video (linked from another comment), the reason those are there is to justify splitting the list of elements into rows in those particular places. The reasoning today is to do with eletron shells (I'm not a chemist but I presume that electron shells are also the root cause of those formulae) but at the time periodic table was created electrons hadn't yet been discovered!

apo 8y ago
You are right (slaps forehead), and I was not thinking about the historical context. The earliest tables were based on "valence", or the ratio with which an element tended to combine with other elements in compounds. Two of the most consistent and easily obtained compounds are those of hydrogen and oxygen, which nearly always combine with other "monovalent" elements in ratios of 1 and 2, respectively. When a new element was discovered, the ratios with which it formed oxides and hydrides could be determined, and this would allow its placement on the table. A student from the late 1800s would only be able to think in terms of equivalents, not electrons and their orbitals - as you point out. The inclusion of hydride and oxide formula templates would have been an integral part of using the table.