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The colors of the γ-sesquisulfides are La 2 S 3, white/yellow; Ce 2 S 3, dark red; Pr 2 S 3, green; Nd 2 S 3, light green; Gd 2 S 3, sand; Tb 2 S 3, light yellow and Dy 2 S 3, orange. [60] The shade of γ-Ce 2 S 3 can be varied by doping with Na or Ca with hues ranging from dark red to yellow, [ 49 ] [ 60 ] and Ce 2 S 3 based pigments are used ...
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]
In chemistry, an unpaired electron is an electron that occupies an orbital of an atom singly, rather than as part of an electron pair. Each atomic orbital of an atom (specified by the three quantum numbers n, l and m) has a capacity to contain two electrons ( electron pair ) with opposite spins .
The localized orbital corresponding to one O-H bond is the sum of these two delocalized orbitals, and the localized orbital for the other O-H bond is their difference; as per Valence bond theory. For multiple bonds and lone pairs, different localization procedures give different orbitals.
The hexaaquacopper(II) ion [Cu(H 2 O) 6] 2+ (21 e −) TM(CO) 8 − (TM = Sc, Y) (20 e −) Often, cases where complexes have more than 18 valence electrons are attributed to electrostatic forces – the metal attracts ligands to itself to try to counterbalance its positive charge, and the number of electrons it ends up with is unimportant.
Most lanthanides can use only three electrons as valence electrons, as afterwards the remaining 4f electrons are too strongly bound: cerium is an exception because of the stability of the empty f-shell in Ce 4+ and the fact that it comes very early in the lanthanide series, where the nuclear charge is still low enough until neodymium to allow ...
The outer valence electrons are more strongly attracted by the nucleus causing the observed increase in ionization potentials. The d-block contraction can be compared to the lanthanide contraction , which is caused by inadequate shielding of the nuclear charge by electrons occupying f orbitals.
The metal also has six valence orbitals that span these irreducible representations - the s orbital is labeled a 1g, a set of three p-orbitals is labeled t 1u, and the d z 2 and d x 2 −y 2 orbitals are labeled e g. The six σ-bonding molecular orbitals result from the combinations of ligand SALCs with metal orbitals of the same symmetry. [8]