2.4 transition metals Flashcards
what is a transition metal?
a metal that can form one or more stable ions with an incomplete d sub-level
which transition metals do you need to know?
period 4 in d-block (titanium to copper)
exceptions to normal electron configuration rules
chromium- prefers to have 1 electron in each orbital of 3d and 1 in 4s so more stable
copper- prefers to have full 3d and 1 in 4s so more stable
why arent Sc and Zn transition metals?
their stable ions dont have incomplete d subshell
Sc only forms Sc3+ which has empty d subshell
Sc is [Ar] 3d1 4s2 so Sc3+ is just [Ar]
zinc only forms Zn2+ which has full d subshell
Zn is [Ar] 3d10 4s2 so Zn 2+ is [Ar] 3d10
physical properties of transition metals
all have high density
all have high melting and boiling points
chemical properties of transition metals
can form complex ions
form coloured ions
good catalysts
exist in variable oxidation states
Ti oxidation states and colours
Ti2+ = +2, violet
Ti3+ = +3, purple
V oxidation states and colours
V2+ = +2, violet
V3+ = +3, green
VO^2+ = +4, blue
VO2^+ = +5, yellow
Cr oxidation states and colours
Cr3+ = +3, green
Cr2O7^2- = +6, orange
Mn oxidation states and colours
Mn2+ = +2, very pale pink/ colourless
MnO4^2- = +6, green
MnO4^- = +7, purple
Fe oxidation states and colours
Fe2+ = +2, pale green
Fe3+ = +3, yellow
Co oxidation states and colours
Co2+ = +2, pink
Ni oxidation states and colours
Ni2+ = +2, green
Cu oxidation states and colours
Cu2+ = +2, pale blue
why do transition metals show variable oxidation states?
the energies of the 4s and 3d subshells are very similar so diff numbers of electrons can be gained/ lost using fairly similar amounts of energy
what is a complex ion?
a metal surrounded by co-ordinately bonded ligands
eg [Cu(H2O)6]2+
what is a co-ordinate bond?
covalent bond in which both electrons in the shared pair come from the same atom
what is a ligand?
an atom/ ion/ molecule that donates a pair of electrons to a central metal ion
what is a monodentate ligand?
a ligand that can only form one co-ordinate bond
eg NH3, Cl-, H2O
what is a multidentate ligand?
a ligand that can form more than one co-ordinate bond
eg EDTA^4-
what are bidentate ligands?
multidentate ligands that can form 2 co-ordinate bonds
eg NH2CH2CH2NH2
how can you work out the oxidation state of a metal ion in a complex?
total charge of complex - sum of charges of ligands
what is co-ordinate number?
what does this determine?
number of co-ordinate bonds formed with central metal ion
determines the shape of the complex ion
what is the shape of a complex ion with 6 coordinate bonds?
octahedral
often hexaaqua (6 water ligands)
what is the shape of a complex ion with 4 coordinate bonds?
tetrahedral
but in a few, may be square planar
eg (PtCl2(NH3)2)
what is the shape of a complex ion with 2 coordinate bonds?
linear
eg [Ag(NH3)2]+
why can you fit 6 H2O or NH3 ligands around a central metal ion but only 4 Cl- ligands?
because H2O and NH3 ligands are small and Cl- ligands are larger
when does optical isomerism occur in complex ions?
when it can occur as 2 non-superimposable mirror images
happens in octahedral complexes where 3 bidentate ligands are attached to the central ion
what is cis-trans isomerism?
occurs in square planar complex ions that have 2 pairs of ligands
trans- 2 paired ligands are directly opposite each other
cis- 2 paired ligands are next the each other
what is cisplatin?
complex of platinum(II) with 2 chloride ions and 2 ammonia molecules in a square planar shape
what can cisplatin be used for?
treat some types of cancer
prevents cancer cells reproducing (more info in booklet?)
downside of using cisplatin?
prevents some healthy cells from reproducing eg blood and hair
causes hair loss, supressed immune system, kidney damage
how can octahedral complex ions show cis-trans isomerism?
octahedral complexes with 4 ligands of 1 type and 2 of another
trans- 2 odd ligands opposite each other
cis- 2 odd ligands next to each other
