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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 ...
The lanthanides become harder as the series is traversed: as expected, lanthanum is a soft metal. Lanthanum has a relatively high resistivity of 615 nΩm at room temperature; in comparison, the value for the good conductor aluminium is only 26.50 nΩm.
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]
The general electronic configuration of the d-block atoms is [noble gas](n − 1)d 0–10 ns 0–2 np 0–1. Here "[noble gas]" is the electronic configuration of the last noble gas preceding the atom in question, and n is the highest principal quantum number of an occupied orbital in that atom.
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.
A block of the periodic table is a set of elements unified by the atomic orbitals their valence electrons or vacancies lie in. [1] The term seems to have been first used by Charles Janet. [2] Each block is named after its characteristic orbital: s-block , p-block , d-block , f-block and g-block .
For transition metals, the number of valence electrons ranges from 3 to 12 (ns and (n−1)d orbitals). For lanthanides and actinides, the number of valence electrons ranges from 3 to 16 (ns, (n−2)f and (n−1)d orbitals). All other non-valence electrons for an atom of that element are considered core electrons.
Since the parent ion can only be 2 P 1/2 or 2 P 3/2, the notation can be shortened to [] or ′ [], where nℓ means the parent ion is in 2 P 3/2 while nℓ′ is for the parent ion in 2 P 1/2 state. Paschen notation is a somewhat odd notation; it is an old notation made to attempt to fit an emission spectrum of neon to a hydrogen-like theory.