Transition elements Flashcards
d-block element
An element with its highest energy e- in the d-subshell
transition metal
A d-block element which forms at least one ion with an incomplete d-subshell
What three types of reactions can transition elements undergo?
- ligand exchange
- precipitate
- redox
chemical properties of transition elements (4)
- colourful
- good catalysts
- variable oxidation states
- complex ions with variety of ligands
physical properties of transition elements (5)
- ductile
- malleable
- high melting/boiling pt
- hard/dense
- sonorous
Why are transition elements good catalysts?
- variable oxidation states
- provide a surface which can absorb reactants (form complex ions)
two examples of reactions which use transition metals as catalysts
- Ni (alkene –> alkane)
- V2O5 Contact process (SO2 + O2 –> 2SO3)
ligand
A molecule or ion that can donate a pair of e- to the transition metal ion
complex ion
A transition metal bonded to ligands by coordinate bonds
coordinate number
Total number of coordinate bonds between a central metal ion and ligands
shape of complex ion with 4 coordinate bonds
square planar (90°)
shape of complex ion with 6 coordinate bonds
octahedral (90°)
bidentate ligands
ligands with two lone pairs of e-:
- en
- ethanedioate (2-)
hexadentate ligands
ligands with six lone pairs of e-:
- edta (4-)
neutral ligands (monodentate)
- H2O
- NH3
charged ligands
- Cl-
- OH-
- CN-
- SCN-
which two transition metals have unusual e- configurations?
Cr and Cu
which d-block elements are not transition elements?
- Zn (Zn2+ has a full d-subshell)
- SC (Sc3+ doesn’t have a d-subshell)
Cu2+ with NaOH(aq)
blue solution –> blue ppt
Cu(OH)2(s)
ppt insoluble in excess
Fe2+ with NaOH(aq)
pale green solution –> dark green ppt (goes brown on standing in air)
Fe(OH)2(s)
ppt insoluble in excess
Fe3+ with NaOH(aq)
pale yellow solution –> orange brown ppt
Fe(OH)3(aq)
ppt insoluble in excess
Mn2+ with NaOH(aq)
pale pink solution –> light brown ppt (darkens on standing in air)
Mn(OH)2(s)
ppt insoluble in excess
Cr3+ with NaOH(aq)
violet solution –> grey green ppt
Cr(OH)3(s)
ppt dissolves in excess to form a dark green solution
[Cr(OH)6]3-(aq)
which ions react the same way with NH3(aq) as they do with NaOH(aq)
Fe2+
Fe3+
Mn2+
Cu2+ with NH3(aq)
blue solution –> blue ppt
Cu(OH)2(s)
ppt dissolves in excess to form a dark blue solution (ligand exchange)
[Cu(NH3)4(H2O)2]2+(aq)
Cr3+ with NH3(aq)
violet solution –> grey green ppt
Cr(OH)3(s)
ppt dissolves in excess to form a purple solution (ligand exchange)
[Cr(NH3)6]3+(aq)
