transition metals 1.3 Flashcards
d block transition metals
metals with an incomplete d subshell in at least one of their ions
oxidation state
describes the no of electrons involved in bonding, transition metals can have a different oxidation states when it forms compounds, different oxidation states have different colours
oxidation numbers
1 uncombined elements = 0
2 single atoms = ion charge
3 oxygen usually -2
4 hydrogen usually +1
5 the sum of all the oxidation numbers in a neutral = 0
6 the sum of all the oxidation numbers in a polyatomic ion = charge on the ion
oxidation =
increase in ox number
reduction =
decrease in ox number
a high ox number usually =
oxidising agent
a low ox number usually =
reducing agent
ligands
they’re negative ions or molecules with a non bonding pair of electrons, they can donate both of these to another atom, this is a special type of covalent bond called a dative bond
how are ligands classified
based on how many electron pairs they donate (and therefore how many dative bonds they form)
monodente
1 pair
bidentate
2 pairs (oxalato)
hexadente
6 pairs (EDTA)
transition metal complex
when a ligand forms a dative bond with a central transition metal atom or ion
coordination number
the number of bonds from a ligands to the central atom and helps determine the shape
aqua
OH2
charge 0
ammine
NH3
charge 0
cyanido
CN-
charge -1
chlorido
Cl-
charge -1
fluorido
F-
charge -1
bromido
Br-
charge -1
iodido
I-
charge -1
hydroxido
OH-
charge -1
oxalato
O2C2O2 / C2O4 2-
charge -2
complex formulae
1 the symbol of the metal is written first, then ligands in alphabetical order based on the letter/symbol that binds to the TM
2 the formula of the complex ion is enclosed within square brackets with the charge outside the square bracket with the charge outside the square brackets eg [FeCl2(OH2)4]+
complex names
1 ligands are named in alphabetical order followed by the metal (and it’s oxidation state in roman numerals)
2 if there is more than one ligand it is preceded by di, tri, tetra etc
3 if the complex is a negative ion overall, the metal ends in ate
4 if the complex is a salt, the name of the positive ion proceeds the name of the negative ion
iron as a negative ion
ferrate
copper as a negative ion
cuprate
when are d orbitals degenerate
whey there are no ligands attached to a transition metal ion
when do d orbitals split
when ligands attach and this is due to the electrostatic repulsion of the approaching ligand
strong field ligand =
large split = large energy difference
weak field ligand =
small split = small energy difference
how to get a spectrochemical series
placing ligands in order of splitting ability
ligands in order of increasing splitting ability
Cl- < OH- < H2O < NH3 < CN- < CO
the two types of catalysts
heterogeneous and homogeneous
heterogeneous catalysts
-reactant molecules absorb into the metal surface
-unpaired d electrons or infilled orbitals allow an activated complex to form by weakening the bonds within the reactant
-this provides a reaction pathway with a lower energy
homogeneous catalysts
-can allow intermediate complexes to form due to the ability to have different oxidation states
-this gives a lower energy pathway for the reaction
