Question

Which of the following statement is wrong? (1) Transition elements lie between III and IV groups in the periodic table. (2) Transition elements are those which contain incomplete d-orbital. (3) The 14 elements placed in the 3rd group and 6 th period of the periodic table are known as rare earths. (4) The clement californium belongs to actinide series.

Short answer

The statement that is wrong is statement (1).

Step-by-step solution

Understanding Transition Elements

Transition elements are defined as those which have incomplete d-orbital. This indicates that statement (2) is correct.

Placement of Transition Elements

Transition elements typically lie between groups III and XII in the periodic table, not specifically between III and IV. Therefore, statement (1) is incorrect.

Identifying Rare Earths

The 14 elements placed in the 3rd group and 6th period are lanthanides, also known as rare earths. Thus, statement (3) is correct.

Actinide Series

Californium (Cf) is an element in the actinide series, so statement (4) is correct.

Key concepts

Periodic Table Groups

The periodic table is a way of organizing elements according to their atomic structure and properties.
It is divided into 18 groups and 7 periods.
Groups are the columns and periods are the rows. Elements in the same group share similar chemical properties.
For example, all elements in Group 1 are alkali metals and they react similarly with water.
Transition elements, often called transition metals, are found in the central part of the table. They typically sit between Group 3 and Group 12.

• This central block is sometimes referred to as the d-block.
• Transition elements have unique properties such as forming colored compounds.

Understanding the placement and properties of these elements helps in predicting their behavior in chemical reactions.

d-orbital Incompleteness

Transition elements are characterized by their incomplete d-orbitals.
Orbitals are regions around an atom's nucleus where electrons are likely to be found.
The d-orbital can hold up to 10 electrons, but in transition metals, it is not fully filled.

• This partial filling gives these elements unique properties like forming complex ions.
• They often show variable oxidation states, meaning they can lose different numbers of electrons.

This variability allows transition elements to form a wide range of compounds. For example, iron can exist in oxidation states of +2 and +3, leading to different types of iron compounds.
Understanding d-orbital incompleteness is key to grasping why transition elements are so versatile.

Rare Earth Elements

Rare earth elements are a group of 17 elements, including the 15 lanthanides plus scandium and yttrium.
They are found in Group 3 and the 6th and 7th periods of the periodic table.
The lanthanides, which are specifically mentioned in the exercise, are often called 'rare earths' because they were difficult to isolate in the past.

• These elements are known for their high magnetic strength and are essential in many modern technologies.
• Lanthanides are used in industries ranging from electronics to renewable energy.

Despite their name, most of them are relatively abundant in the Earth's crust.
Understanding where these elements lie and their unique properties is crucial for studying advanced materials and technologies.

Actinide Series

The actinide series consists of 15 elements that range from actinium (Ac) to lawrencium (Lr).
These elements fill the 5f orbital and are located in the 7th period of the periodic table.
Actinides are known for being radioactive.

• They include elements like uranium and thorium, which are used in nuclear reactors and weapons.
• Californium (Cf), specifically mentioned in the exercise, is used in neutron radiography and as a neutron source.

Most actinides are not found naturally and must be synthesized in laboratories.
Understanding the actinide series is significant for nuclear chemistry and various applications in energy and medicine.