With an atomic structure wholly different from that of the rare earth inner transition series, does lanthanum even belong with the rare earth elements?
By: Ringo Bones
Element 57, lanthanum, symbol La, can be considered a maverick among the rare earth elements. In the strictest sense, it is not actually a member of the rare earth inner transition series since it does not have a 4f-electron. Lanthanum’s differentiating electron – from barium – is found in the 5d-orbital. And yet lanthanum’s chemical properties so resemble those of rare earth metals that analytical chemists for much of the 20th Century had placed lanthanum among the rare earth elements.
Given that the Periodic Table of the Elements is based on the periodic law – which according to the wisdom and insight of Dimitri Ivanovich Mendeleyev – revolves around the law in chemistry where he ordered the elements in the sequence of their increasing atomic numbers that show a periodic – as in chemical property variation – in most of their properties. Because of this, groupings of elements are decided more on their chemical properties rather than their atomic structure.
And lanthanum’s chemical properties does resemble very much like that of its rare earth sister metals as opposed to the first transition metals where it resembles in atomic structure. At present, the International Union of Pure and Applied Chemistry (IUPAC) still places lanthanum snugly within the confines of the rare earth metals group even though its atomic structure is a bit suspect for a true blue rare earth element.
Showing posts with label Rare Earth Chemical Properties. Show all posts
Showing posts with label Rare Earth Chemical Properties. Show all posts
Saturday, November 13, 2010
Is Yttrium a Rare Earth Element?
Currently being grouped with titanium and zirconium in the first transition metals, does the element yttrium rightfully belong among the rare earth elements?
By: Ringo Bones
Named after the town of Ytterby, Sweden where it was first discovered in 1794; yttrium is a scaly metal with an iron-gray sheen. Primarily used in making phosphors for color TV screens and Microwave filters, yttrium is also well-known in the medical community in the form of yttrium-90, a radioactive isotope that had gained dramatic medical use in needles that had replaced the surgeon’s knife in killing pain-transmitting nerves in the spinal cord. But with an atomic structure and chemical properties resembling more of the rare earths instead of the first transition metals, does this make yttrium a rare earth metal?
From the analytical chemists’ perspective, yttrium, Y, resembles the rare earths more strongly than it does scandium in spite of the fact that it has no 4f-electrons in common with the rare earths. When a rare earth ore is digested with sulfuric acid or fused with potassium bisulfate and the sulfates fractionally crystallized, yttrium is found with the sulfates of dysprosium, holmium, erbium, thulium, ytterbium and lanthanum – the heavy members of the rare earths – in the most soluble fraction. Separation of the Y (III) ion from the other rare earths is achieved most economically and in the highest purity by either ion-exchange or solvent extraction procedures. The hydroxides and oxides of yttrium are somewhat stronger and more soluble than those of terbium but weaker than those of lanthanum. The compound - in general - resembles those of the rare earths of high atomic number – i.e. at the end of the series like ytterbium and lutetium.
For sometime now, the Union of Pure and Applied Chemistry (IUPAC) has placed yttrium in the Group III B of the Periodic Table of the Elements. Chemically, yttrium does possess some very intriguing chemical properties that make it behave as if it is a rare earth element and yet yttrium has no 4f-electrons in common with the rare earths. Given that Dimitri Mendeleyev constructed the Periodic Table of the Elements primarily to arrange individual elements by chemical properties while their atomic structure is of only secondary importance, shouldn’t yttrium belong to the rare earth group of elements instead of in the first transition metals?
By: Ringo Bones
Named after the town of Ytterby, Sweden where it was first discovered in 1794; yttrium is a scaly metal with an iron-gray sheen. Primarily used in making phosphors for color TV screens and Microwave filters, yttrium is also well-known in the medical community in the form of yttrium-90, a radioactive isotope that had gained dramatic medical use in needles that had replaced the surgeon’s knife in killing pain-transmitting nerves in the spinal cord. But with an atomic structure and chemical properties resembling more of the rare earths instead of the first transition metals, does this make yttrium a rare earth metal?
From the analytical chemists’ perspective, yttrium, Y, resembles the rare earths more strongly than it does scandium in spite of the fact that it has no 4f-electrons in common with the rare earths. When a rare earth ore is digested with sulfuric acid or fused with potassium bisulfate and the sulfates fractionally crystallized, yttrium is found with the sulfates of dysprosium, holmium, erbium, thulium, ytterbium and lanthanum – the heavy members of the rare earths – in the most soluble fraction. Separation of the Y (III) ion from the other rare earths is achieved most economically and in the highest purity by either ion-exchange or solvent extraction procedures. The hydroxides and oxides of yttrium are somewhat stronger and more soluble than those of terbium but weaker than those of lanthanum. The compound - in general - resembles those of the rare earths of high atomic number – i.e. at the end of the series like ytterbium and lutetium.
For sometime now, the Union of Pure and Applied Chemistry (IUPAC) has placed yttrium in the Group III B of the Periodic Table of the Elements. Chemically, yttrium does possess some very intriguing chemical properties that make it behave as if it is a rare earth element and yet yttrium has no 4f-electrons in common with the rare earths. Given that Dimitri Mendeleyev constructed the Periodic Table of the Elements primarily to arrange individual elements by chemical properties while their atomic structure is of only secondary importance, shouldn’t yttrium belong to the rare earth group of elements instead of in the first transition metals?
Is Scandium A Rare Earth Element?
Currently being grouped with titanium and zirconium in the First Transition Metals part of the periodic table, does the element scandium rightfully belong in the rare earth metals section of the Periodic Table?
By: Ringo Bones
The last time scandium gained widespread press coverage was back in the mid 1990s when this “space age” first transition metal was used in the manufacture of light weight but strong revolvers and related handguns due to the fact that scandium is as light as aluminum but with a much higher melting point. Progress then for such an under-utilized “space age” metal since chemically pure scandium was only produced in one pound quantities only as recently in 1960. But the question now is, does scandium belong to in the rare earth “leg” of the Periodic Table rather than in the first transition metals group?
Even though the International Union of Pure and Applied Chemistry or IUPAC has since placed scandium in the Group III B of the first transition metals, it does have chemical properties and an atomic structure that eerily mimics that of the lanthanide or rare earth elements. During the “space age” science boom of the 1960s, the element scandium, Sc, is usually associated chemically with the lanthanide or rare earth elements of atomic numbers 57 to 71, although its electron structure does not conform to this long series system. Scandium’s differentiating electron, compared to its predecessor, calcium, is in a (n-1) state rather than a (n-2) level. Scandium is found to be a slight fraction of the total in rare-earth minerals – such as monazite, gadolinite, etc. The most abundant source of scandium is the mineral thortveitite.
To separate the element, the ore is first digested with strong sulfuric acid or fused with potassium hydrogensulfate. Water treatment removes the soluble sulphate salts. Unwanted heavy metals are removed by precipitation as sulfides or by careful adjustment of the hydroxide-ion concentration. All of the rare earths, including scandium, are precipitated by addition of oxalic acid. Finally, scandium is separated from the other elements – all of which form soluble oxalates – by forming a sulfate called scandium sulfate pentahydrate which is more soluble than the rare earth sulfates.
Scandium has also been prepared by the electrolysis of its fused chloride on a zinc cathode. The zinc metal is removed from the deposited scandium metal by volatilizing the former. Scandium differs from the other members of the Group III B elements in forming less-basic oxides, though the oxide is still not amphoteric – i.e. soluble in excess base. The chloride is more volatile and the nitrate more easily decomposed. The complexes are somewhat more stable, and surprisingly is the fact that it will form a normal carbonate in view of the relatively small size and the high charge exhibited by the trivalent ion of scandium.
For sometime now, the Union of Pure and Applied Chemistry (IUPAC) has placed scandium in the Group III B of the Periodic Table of the Elements even though chemically, it does possess some very intriguing chemical properties that make it behave as if it is a rare earth element. Given that Mendeleyev’s “construction” of the Periodic Table of the Elements primarily sorts the individual elements by their chemical properties while atomic structure is only a notch below this in terms of importance, shouldn’t scandium be a rare earth element because it has rare earth chemical properties?
By: Ringo Bones
The last time scandium gained widespread press coverage was back in the mid 1990s when this “space age” first transition metal was used in the manufacture of light weight but strong revolvers and related handguns due to the fact that scandium is as light as aluminum but with a much higher melting point. Progress then for such an under-utilized “space age” metal since chemically pure scandium was only produced in one pound quantities only as recently in 1960. But the question now is, does scandium belong to in the rare earth “leg” of the Periodic Table rather than in the first transition metals group?
Even though the International Union of Pure and Applied Chemistry or IUPAC has since placed scandium in the Group III B of the first transition metals, it does have chemical properties and an atomic structure that eerily mimics that of the lanthanide or rare earth elements. During the “space age” science boom of the 1960s, the element scandium, Sc, is usually associated chemically with the lanthanide or rare earth elements of atomic numbers 57 to 71, although its electron structure does not conform to this long series system. Scandium’s differentiating electron, compared to its predecessor, calcium, is in a (n-1) state rather than a (n-2) level. Scandium is found to be a slight fraction of the total in rare-earth minerals – such as monazite, gadolinite, etc. The most abundant source of scandium is the mineral thortveitite.
To separate the element, the ore is first digested with strong sulfuric acid or fused with potassium hydrogensulfate. Water treatment removes the soluble sulphate salts. Unwanted heavy metals are removed by precipitation as sulfides or by careful adjustment of the hydroxide-ion concentration. All of the rare earths, including scandium, are precipitated by addition of oxalic acid. Finally, scandium is separated from the other elements – all of which form soluble oxalates – by forming a sulfate called scandium sulfate pentahydrate which is more soluble than the rare earth sulfates.
Scandium has also been prepared by the electrolysis of its fused chloride on a zinc cathode. The zinc metal is removed from the deposited scandium metal by volatilizing the former. Scandium differs from the other members of the Group III B elements in forming less-basic oxides, though the oxide is still not amphoteric – i.e. soluble in excess base. The chloride is more volatile and the nitrate more easily decomposed. The complexes are somewhat more stable, and surprisingly is the fact that it will form a normal carbonate in view of the relatively small size and the high charge exhibited by the trivalent ion of scandium.
For sometime now, the Union of Pure and Applied Chemistry (IUPAC) has placed scandium in the Group III B of the Periodic Table of the Elements even though chemically, it does possess some very intriguing chemical properties that make it behave as if it is a rare earth element. Given that Mendeleyev’s “construction” of the Periodic Table of the Elements primarily sorts the individual elements by their chemical properties while atomic structure is only a notch below this in terms of importance, shouldn’t scandium be a rare earth element because it has rare earth chemical properties?
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