Families of Elements II: Transition & Rare Earth Elements – SS2 Chemistry Lesson Note (First Term)

Transition elements are found between groups II and III of the periodic table. Lanthanides, or rare earth elements, are 15 similar elements in period six, from lanthanum to lutetium. Actinides are found in period seven, from actinium to lawrencium. Elements with atomic numbers 93 to 103 are artificial, because they do not occur naturally.

Behavioural objectives

By the end of the lesson, students should be able to:

• state where transition elements are found in the periodic table and name the elements of the first transition series;
• list the properties of transition elements;
• name the lanthanides (rare earth elements) and state their period and number;
• name the actinides and state their period;
• explain why elements with atomic numbers 93 to 103 are called artificial elements.

What are transition elements?

Transition elements are found between groups II and III of the periodic table. The first transition series consists of the following elements: Scandium (Sc), Titanium (Ti), Vanadium (V), Chromium (Cr), Manganese (Mn), Iron (Fe), Cobalt (Co), Nickel (Ni), Copper (Cu) and Zinc (Zn).

Properties of transition elements

1. High tensile strength
2. High melting and boiling points
3. Variable oxidation states
4. Formation of coloured ions
5. Formation of complex ions
6. Paramagnetic in mixture
7. Catalytic ability

What are lanthanides (rare earth elements)?

Lanthanides are found in period six. The series begins with Lanthanum (La) and ends with Lutetium (Lu). There are 15 of them altogether, and they resemble one another greatly.

What are actinides and artificial elements?

The actinides are similar to the lanthanides. They are found in the seventh period, which starts with Actinium (Ac) and ends with Lawrencium (Lr). Uranium, a well-known element, is in this group.

The elements with atomic numbers from 93 to 103 are known as the artificial elements. This is because they do not occur naturally but are formed during nuclear reactions.

Evaluation

1. Name the elements of the first transition series.
2. State four properties of transition elements.
3. In which period are the lanthanides found, and how many are there?
4. Which element begins the actinide series and which one ends it?
5. Why are the elements with atomic numbers 93 to 103 called artificial elements?

Assignment

1. Hydrogen can be placed in group I or group VII. Explain.
2. Write the electronic configuration of the following elements and state the group and period to which each belongs: ₆C, ₁₁Na, ₁₄Si, ₁₈Ar.