Topic 13.1: First row d-block elements Flashcards
Definition of transition metals
Elements whose atoms have incomplete d-orbitals or can form positive ions with an incomplete d sub-level (Group 3 – 11)
Which element in the first row d-block elements is not a transition metal?
Zn does not form partially filled d orbitals
Physical properties of transition metals
a) High electrical and thermal conductivity
b) High melting point
c) Malleable
d) Ductile
e) Magnetic
Chemical properties of transition metals
a) Variable oxidation states
b) Formation of complex ions with ligands
c) Colored compounds
d) Catalytic behavior
Explanation of the cause of variable oxidation states in transition metals
No significant increase in successive ionization energies in transitions metals as the 3d and 4s orbitals are close in energy. Transition metals can lose varying number of electrons with the same relative ease
What oxidation number can all transition metals form?
+2
Definition of ligands
Molecules or anions with at least one lone pair of electrons that form coordinate covalent bonds with a central metal ion
Lewis bases and acids in complex ions
a) Metal ions act as lewis acids by accepting electron pairs
b) Ligands act as lewis bases by donating electron pairs
Denticity
Number of donor groups in a single ligand that bind to a central atom in a coordination complex
Monodentate ligands
Use one lone pair of electrons
a) H2O
b) CN-
Bidentate ligands
Use two lone pairs of electrons
a) ethanediamine
b) Oxalate -2
Hexadentate ligands
Use six lone pairs of electrons
a) EDTA-41a
Complex ions
Transition metal ions in solution have high charge density and attract water molecules which form coordinate bonds with the positive ions to form a complex ion
Coordinate bond definition
Bond which uses a lone pair of electrons to form a covalent bond
Coordination number definition
Number of coordinate bonds from the ligands to the central ion
Geometry of complex ions according to coordination number
a) Linear (2)
b) Square planar (4)
c) Tetrahedral (4)
d) Octahedral (6)
Definition of a catalyst
Substance which increases the rate of a chemical reaction by lowering the activation energy
Why are transition metals good heterogeneous catalysts?
Form weak bonds with reactant molecules and provide a surface for the reactant molecules to come together
Examples of heterogeneous catalytic properties in transition metals
a) Haber process, 3H2 + N2 => 2NH3(Fe)
b) Hydrogenization of alkenes to alkanes (Ni)
c) Removal of CO and NO (Pd, Pt)
d) Decomposition of H2O2 (MnO2)
e) Contact process, 2SO2 + O2 => 2SO3 (V2O3)
Why are transition metals good homogeneous catalysts?
Show variable oxidation states allows them to be effective in redox reactions
Examples of homogeneous catalytic properties in transition metals
Fe2+ in heme
Co3+ in vitamin B
Where do the paramagnetic properties of transition metals come from?
Unpaired electrons in orbitals (which are negatively charged and spinning) create a small magnetic field itself
Where do the diamagnetic properties of transition metals come from?
If all the electrons are paired, the effect of the spinning is cancelled out – so the small magnetic field is not created
Diamagnetic properties
Unpaired electrons. Weakly repelled by a magnetic field
Paramagnetic properties
a) One or more unpaired d-orbital electrons. Attracted by an external field
Ferromagnetic properties
Only occurs in Fe, Co, and Ni. The attraction to a magnetic field is much stronger
