Electronic Configurations and Types of Elements - The f-Block Elements (Inner-transition Elements)

The electronic configuration of gadolinium (Atomic number 64) is ______.

Write the general outer electronic configuration of f- block elements.

The most common oxidation state of actinoids is ____________.

What are actinoids? Give three examples.

In the modern periodic table, elements are arranged in order of increasing atomic numbers which is related to the electronic configuration. Depending upon the type of orbitals receiving the last electron, the elements in the periodic table have been divided into four blocks, viz, s, p, d and f. The modern periodic table consists of 7 periods and 18 groups. Each period begins with the filling of a new energy shell. In accordance with the Arfbau principle, the seven periods have 2, 8, 8, 18, 18, 32 and 32 elements respectively. The seventh period is still incomplete. To avoid the periodic table being too long, the two series of f-block elements, called lanthanoids and actinoids are placed at the bottom of the main body of the periodic table.

Which of the elements whose atomic numbers are given below, cannot be accommodated in the present set-up of the long form of the periodic table?

Given below are two statements: One is labelled as Assertion A and the other is labelled as Reason R:

Assertion A: Size of Bk³⁺ ion is less than Np³⁺ ion.

Reason R: The above is a consequence of the lanthanoid contraction.

In the light of the above statements, choose the correct answer from the options given below:

The actinoid elements which show the highest oxidation state of +7 are ____________.

What is lanthanoid contraction and what are the effects of lanthanoid contraction?