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All of the lanthanides form sesquioxides, Ln 2 O 3. The lighter/larger lanthanides adopt a hexagonal 7-coordinate structure while the heavier/smaller ones adopt a cubic 6-coordinate "C-M 2 O 3" structure. [50] All of the sesquioxides are basic, and absorb water and carbon dioxide from air to form carbonates, hydroxides and hydroxycarbonates. [57]
Lanthanide metals react exothermically with hydrogen to form LnH 2, dihydrides. [1] With the exception of Eu and Yb, which resemble the Ba and Ca hydrides (non-conducting, transparent salt-like compounds),they form black pyrophoric, conducting compounds [6] where the metal sub-lattice is face centred cubic and the H atoms occupy tetrahedral sites. [1]
About 40-50% of the actinide contraction has been attributed to relativistic effects. [2] A decrease in atomic radii can be observed across the 5f elements from atomic number 89, actinium, to 102, nobelium. This results in smaller than otherwise expected atomic radii and ionic radii for the subsequent d-block elements starting with 103, lawrencium.
The one thing that is uniform across periodic tables is that a given table will follow the same convention for lanthanides and actinides. If the lanthanides are 57-70, the actinides are 89-102; if the lanthanides are 57-71, the actinides are 89-103; if the lanthanides are 58-71, the actinides are 90-103.
Plutonium is a transuranic radioactive chemical element, an actinide metal. Actinide chemistry (or actinoid chemistry) is one of the main branches of nuclear chemistry that investigates the processes and molecular systems of the actinides. The actinides derive their name from the group 3 element actinium.
While the later actinides from americium onwards are predominantly trivalent and behave more similarly to the corresponding lanthanides, as one would expect from periodic trends, the early actinides up to plutonium (thus including thorium and uranium) have relativistically destabilised and hence delocalised 5f and 6d electrons that participate ...
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The lanthanide contraction only partially accounts for this anomaly. [11] Because the 6s 2 orbital is contracted by relativistic effects and may therefore only weakly contribute to any chemical bonding, Hg–Hg bonding must be mostly the result of van der Waals forces. [11] [13] [14] Mercury gas is mostly monatomic, Hg(g).