5.7 - Transition elements Flashcards
Define d-block element
highest energy electron is in a d sub-shell (Sc-Zn)
Define transition metal
d-block element that forms at least 1 ion with a partially filled d sub-shell (Ti-Cu)
Which elements fill 4s1 instead of 4s2 for greater stability?
- chromium
- copper
Which elements are NOT transition metals?
- scandium (empty d-orbital)
- zinc (full d-orbital)
Characteristics of transition metals
- form compounds w/ different oxidation states
- form coloured compounds
- elements/compounds can act as catalysts
What are often strong oxidising agents?
species with transition metal in highest oxidation state
How do complex ions form?
1+ molecules/negative ions (ligands) bond to central metal ion
NB: can form with elements other than transition metals
Define ligand
molecule/ion that donates a lone pair of electrons to central metal ion to form dative covalent (coordinate bond) with metal ion
What is a coordination number?
number of coordinate bonds attached to a central metal ion
Define monodentate ligand and give common examples and their charges
ligand able to donate 1 electron pair to central metal ion
examples:
- H2O: (neutral)
- :NH3 (neutral)
- :Cl- (-1)
- :CN- (-1)
- :OH- (-1)
Define bidentate ligand
ligand that can donate 2 lone pairs
e.g 1,2-diaminoethane
Which central metal ions form square planar complexes, why, and give bond angle
Pt, Pd, Au
90 degrees
occurs in transition metals with 8 electrons in highest energy d sub-shell
Cis-trans isomerism in complex ions
- octahedral (4 of 1 ligand/2 bidentate, and 2 of other) or square planar
- cis: identical groups adjacent (90°)
- trans: identical groups opposite (180°)
When does optical isomerism occur?
in complexes with 2+ bidentate ligands
Describe the use of cis-platin as an anti-cancer drug
- attacks tumours and shrinks them by forming Pt complex inside cell
- binds to DNA, preventing replication and cell division
