Transition Metals

Question 1

Transition metal def

Answer 1

A metal that forms one or more stable cations with a partially filled d sub-shell

Question 2

Why aren’t scandium and zinc transition metals?

Answer 2

As ions, scandium has no electrons in the d sub shell and zinc has a full d sub shell - neither are partially filled

Question 3

Why do transition metals show variable oxidation numbers?

Answer 3

The 4s sub shell and the 3d subshell have very similar energies

Question 4

Properties of transition elements

Answer 4

Have variable oxidation states, form metal complexes, from complex compounds, good catalysts, form coloured ions in solutions

Question 5

Ligand def

Answer 5

A species which can donate a lone pair of electrons to an empty d-orbital to form a dative covalent bond

Question 6

Complex ions

Answer 6

A central metal ion surrounded by ligands bonded to it by dative covalent bonds - has an overall positive or negative charge

Question 7

Naming metal complexes

Answer 7

Cations before anions. Negative ligands before neutral ones. Alphabetical. Number of a group is indicated by a prefix (di/tri/tetra). Negative ligands end in o. If the overall complex is negative, it will end in are. The oxidation state of the metal is given at the end in roman numerals

Question 8

Catalyst for margarine production

Answer 8

Ni (nickel)

Question 9

Catalyst for making SO3 for H2SO4

Answer 9

V2O5

Question 10

Catalyst for Haber process to make ammonia

Answer 10

Fe (iron)

Question 11

Catalytic converters

Answer 11

Pt (platinum) and Pd (palladium)

Question 12

Co-ordination number

Answer 12

Number of co-ordinate (dative covalent) bonds from ligands to metal ions

Question 13

What is used as a chemical test for very small concentrations of Fe3+ ions? Why?

Answer 13

Iron thiocyanate because it is very intensely coloured

Question 14

Where does the origin of coloured compounds come from?

Answer 14

Compounds either emit light of a particular frequency or they absorb light at a particular frequency

Question 15

What are the only stable oxidation states for scandium and zinc?

Answer 15

Zinc (II) and Scandium (III)

Question 16

Which sub-shell has the higher energy?

Answer 16

3d. Hence, 4s is filled first and lost first as 4s electrons have higher energy

Question 17

Why do all transition metals form 2+ ions?

Answer 17

Because the 2 4s electrons are lost

Question 18

What do high oxidation states mean for the transition element?

Answer 18

It acts as a strong oxidising agent as it can easily gain electrons from other substances

Question 19

Ligand field theory

Answer 19

Assumes that the central metal ion interacts with the surrounding ligands electrostatically. The negatively charged ligands interact with the d electrons in the cation because the d orbitals are arranged differently in space

Question 20

Why are ligands degenerate?

Answer 20

In an isolated atom or ion, before any interaction, the five atomic d-orbitals have the same energy

Question 21

Why does the degeneracy of ligands change?

Answer 21

When the ligands attach,the electric fields associated cause repulsion in the d-orbitals that increase their energies

Question 22

How can electrons be promoted from lower 3d-orbitals to upper 3d-orbitals in a transition metal complex?

Answer 22

It must have at least one electron in a lower 3d-orbital and at least one gap in an upper 3d-orbital