transition metals Flashcards
what is a transition metal?
a d block element that is able to form at least one ion with an incomplete d sub shell.
What are four useful properties of TM?
The can form complex ions.
They have variable oxidation states.
The are colourful compounds.
They are good catalysts
Give three physical properties of transition metals.
They are malleable.
High melting/boiling point.
High density.
Why are Sc and Zn not examples of TM?
Despite being in the d sub shell they don’t form ions with an incomplete sub shells.
The 4s sub shell __ and __ before the 3d sub shell. Unless __ or __.
fills and empties
copper or chromium
How can TM easily from ions with different oxidation states?
1st and 2nd ionisation energies are low so it’s easy to lose 4s and 3d electrons.
which oxidation state is most common at the start of the d block?
+3 as it’s easier to lose electrons.
Which oxidation state is most common at the end of the d block?
+2
How does Cu2+ appear blue?
It absorbs red light and reflects blue light so appears blue.
How does Zn2+ appear colourless?
It reflects all light.
How do TM make good catalysts?
They have different oxidation states. Ions have incomplete d such shell available for electrons.
define a homogenous catalyst
Has the same state as the reactants
define heterogeneous catalyst
Different state to the reactants
What is a coordinate bond?
A dative covalent bond when positive metal ion accepts electron pairs from other ions or molecules.
What is a ligand? give examples
A molecule or ion that forms a coordinate bond/dative covalent bond with a central TM ion. It contains a lone pair of electrons. ie water, ammonia, chloride ion or cyanide ion.
what is the coordinate number? What does this tell us about the shape of the molecule?
the number of coordinate bonds formed by the complex metal ion. 6 bonds= octahedral
4 bonds= tetrahedral
2 bonds= linear
what are mono dentate ligands?
Molecules that can form only one bond with central TM ion.
What are the two type of multidentate ligands?
Bidentate - 2 bonds to central metal ion
polydentate - more then 2 bonds ie EDTA
Why are transition metals and their ions good catalysts?
variable oxidation states and provide a surface to absorb reactants.
give four reactions where TM are used as a catalyst.
Ni or Pt in hydrogenation of alkenes
V in contact process
Ca in the decomposition of hydrogen peroxide
Fe in the haber process
what colour are Cu 2+ ions (aq)
blue
what colour are Fe 2+ ions (aq)
(pale) green
what colour are Fe 3+ ions (aq)
what colour are they in NaOH
what colour are they in excess NaOH
yellow (aq)
orange brown ppt (s)
orange brown ppt (s) insoluble
what colour are Cr 3+ ions (aq)
what colour are they in NaOH
what colour are they in excess NaOH
violet
grey- green ppt (s) which dissolves in excess NaoH forming a …
dark green solution (aq)
