24) Transition elements Flashcards
(49 cards)
For which two elements does the expected principle of electrons filling singly in orbitals before pairing does not apply?
Chromium (3d5 4s1) and Copper (3d10 4s1)
the 1/2 full or fully filled 3d sub-shell to give additional stability
Define transition element
a d-block element which forms an ion with an incomplete d-sub-shell
(not Sc -> Sc3+ or Zn -> Zn2+)
Give 3 features of transition elements
- form compounds in which the transition element has different oxidation states
- form coloured compounds
- the element and their compounds can act as catalysts e.g. vanadium (V) oxide in the Contact process - production of sulfur dioxide
What is a species containing a transition element in its highest oxidation state often?
a strong oxidising agent
Define complex ion
a transitional metal ion bonded to ligands by coordinate (dative covalent) bonds
When is a complex ion formed?
when 1 or more molecules / anions (ligands) bond to a central metal ion
Define ligand
a molecule or ion that can donate a pair of e- to the transitional metal ion
Define coordinate bond
a shared pair of e- in which the bonded pair has been provided by one of the bonding atoms only
Define coordination number
the total number of coordinate bonds formed between a central metal ion and ligands
What is the overall charge of a complex ion?
the sum of the charges on the central metal ion and any ligands present
Describe the written formula of a complex ion e.g. [Cr(H2O)6]3+
square brackets used to group all of the parts of the complex ion together
ligand inside round brackets
overall charge of complex outside square brackets
Define monodentate ligand
a ligand that is able to donate 1 pair of e- to a central metal ion
Give 5 examples of monodentate ligands
H2O: \:NH3 \:Cl- cyanide, :CN- \:OH-
Define bidentate ligand
a ligand that can donate two lone pairs f e- to the central metal ion, forming two coordinate bonds
Give 2 examples of bidentate ligand
1,2-diaminoethane ethanedioate ion (oxalate ion)
What does the shape of a complex ion depend upon?
its coordination number
Six-coordinate complexes can form which shape?
octahedral
Four-coordinate complexes can form which 2 shapes?
tetrahedral
square planar
In which complex ions does a square planar shape occur?
in those of transition metals with 8
Describe cis-trans isomerism in octahedral complexes with monodentate ligands
4 of 1 type of ligand and two of another type of ligand
Describe optical isomerism in octahedral complexes
contain 2 or more bidentate ligands
‘cis’ isomers only
What are trans-isomers of octahedral complexes unable to show optical isomerism?
mirror image is exactly the same and can be superimposed
Describe the role of cis-platin in cancer treatment?
forms a platinum complex inside of a cell which binds to DNA, preventing DNA replication
activation of the cell’s own repair mechanism leads to apoptosis
Define ligand substitution
a reaction in which one or more ligands in a complex ion are replaced by different ligands