Topic 13.1: First row d-block elements

Question 1

Definition of transition metals

Answer 1

Elements whose atoms have incomplete d-orbitals or can form positive ions with an incomplete d sub-level (Group 3 – 11)

Question 2

Which element in the first row d-block elements is not a transition metal?

Answer 2

Zn does not form partially filled d orbitals

Question 3

Physical properties of transition metals

Answer 3

a) High electrical and thermal conductivity
b) High melting point
c) Malleable
d) Ductile
e) Magnetic

Question 4

Chemical properties of transition metals

Answer 4

a) Variable oxidation states
b) Formation of complex ions with ligands
c) Colored compounds
d) Catalytic behavior

Question 5

Explanation of the cause of variable oxidation states in transition metals

Answer 5

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

Question 6

What oxidation number can all transition metals form?

Answer 6

+2

Question 7

Definition of ligands

Answer 7

Molecules or anions with at least one lone pair of electrons that form coordinate covalent bonds with a central metal ion

Question 8

Lewis bases and acids in complex ions

Answer 8

a) Metal ions act as lewis acids by accepting electron pairs

b) Ligands act as lewis bases by donating electron pairs

Question 9

Denticity

Answer 9

Number of donor groups in a single ligand that bind to a central atom in a coordination complex

Question 10

Monodentate ligands

Answer 10

Use one lone pair of electrons

a) H2O
b) CN-

Question 11

Bidentate ligands

Answer 11

Use two lone pairs of electrons

a) ethanediamine
b) Oxalate -2

Question 12

Hexadentate ligands

Answer 12

Use six lone pairs of electrons

a) EDTA-41a

Question 13

Complex ions

Answer 13

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

Question 14

Coordinate bond definition

Answer 14

Bond which uses a lone pair of electrons to form a covalent bond

Question 15

Coordination number definition

Answer 15

Number of coordinate bonds from the ligands to the central ion

Question 16

Geometry of complex ions according to coordination number

Answer 16

a) Linear (2)
b) Square planar (4)
c) Tetrahedral (4)
d) Octahedral (6)

Question 17

Definition of a catalyst

Answer 17

Substance which increases the rate of a chemical reaction by lowering the activation energy

Question 18

Why are transition metals good heterogeneous catalysts?

Answer 18

Form weak bonds with reactant molecules and provide a surface for the reactant molecules to come together

Question 19

Examples of heterogeneous catalytic properties in transition metals

Answer 19

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)

Question 20

Why are transition metals good homogeneous catalysts?

Answer 20

Show variable oxidation states allows them to be effective in redox reactions

Question 21

Examples of homogeneous catalytic properties in transition metals

Answer 21

Fe2+ in heme

Co3+ in vitamin B

Question 22

Where do the paramagnetic properties of transition metals come from?

Answer 22

Unpaired electrons in orbitals (which are negatively charged and spinning) create a small magnetic field itself

Question 23

Where do the diamagnetic properties of transition metals come from?

Answer 23

If all the electrons are paired, the effect of the spinning is cancelled out – so the small magnetic field is not created

Question 24

Diamagnetic properties

Answer 24

Unpaired electrons. Weakly repelled by a magnetic field

Question 25

Paramagnetic properties

Answer 25

a) One or more unpaired d-orbital electrons. Attracted by an external field

Question 26

Ferromagnetic properties

Answer 26

Only occurs in Fe, Co, and Ni. The attraction to a magnetic field is much stronger