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, so can act as catalysts
- form coloured compounds
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
coordinate (dative covalent) bonding to a metal atom/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
species with 1 lone pair forming coordinate (dative covalent) bond with central metal atom/ion
examples:
- H2O: (neutral)
- :NH3 (neutral)
- :Cl- (-1)
- :CN- (-1)
- :OH- (-1)
Define bidentate ligand
species with 2 lone pairs of electrons forming coordinate (dative covalent) bonds with central metal atom/ion
e.g NH2CH2CH2NH2
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
binds to DNA, preventing cell division
Define ligand substitution
reaction where 1 ligand in a complex ion is replaced by another
How does CO cause poisoning?
- CO datively bonds to Fe2+ central ion
- CO replaces O2 ligand
- preventing O2 transport as it forms stronger bonds than O2
Define precipitation reaction
2 aqueous solutions containing ions react to form insoluble ionic solid
