13. Periodicity HL

List the characteristic properties of transition elements:

• Variety of Stable Oxidation states (ions with different charges)
• Ability to form complex ions
• Formation of colored ions
• Catalytic Activity

Explain why Sc and Zn are not considered to be transition metals

• Transition metals are defined as elements with a “Partially filled d-orbital”. Sc has an empty 3d orbital while Zn has a full 3d orbital
• Do not have variable oxidation numbers
• The charge of Scandium will always be 3+
• The charge of Zinc will always be 2+
• Do not form colored compounds
• Do not have catalytic properties

Explain the existence of variable oxidation numbers in ions of transition elements

            There is no increase in successive ionization energies in transition metals. There is only a slightly higher effective nuclear charge so there are no great jumps in successive ionization energies. That way, ions can lose varying numbers of electrons with the same relative ease, depending on the oxidative nature of the surrounding environment.

All transition metals have the ionization state 2 +

This is because transition metals easily lose the 4s set of electrons

On the left hand of the transition metals (à Iron), transition metals form increasingly powerful oxidants

Alternate Ions

Chromium forms- 3+ and 6+

Manganese forms 4+ and 7+

Iron forms 3+

Copper forms 1+

Define the term ligand

A Lewis base that can donate a pair of non-bonding electrons to the central metal ion in the complex

Example:

 

 

The Chloride ions serve as the ligands to the central metal

Define and explain the formation of complexes of d-block elements

            Ligands donate a pair of electrons to a central metal ion with a specific charge. This creates a charged particle (equal to the sum of the charges on the ligands and the central metal ion) of a central metal atom with either 2, 4, or 6 ligands (always in even intervals).

Type of bond formed between metals and ligands: dative covalent bond

Coordination Number- the number of ions

Explain why some complexes of d-block elements are colored

            In complex ions, the d sub-level splits into two sets of p-orbitals (one of higher energy and one of lower energy.) Electrons in the lower sub-level become excited, and jump to the higher sub-level. These then fall back to the lower sub-level, releasing energy in the form of light.

State examples of the catalytic action of transition elements and their compounds

Examples:

• V₂O₅ is used in the contact process
• Fe is used in the Haber process
• Fe also is in the heme group of hemoglobin
• Nickel is used to convert alkenes and alkanes
• Cobalt is used in Vitamin B₁₂
• Pd and Pt are catalytic converters