Question

Lanthanides and actinides are recognized as?
(A) S- block elements
(B) d- block elements
(C) F- block elements
(D) P- block elements

Answer 1

Hint: To answer this question, you must recall the occurrence and properties of the elements in the modern periodic table. The periodic table is the arrangement of a total of 118 elements according to their properties. It can be broadly classified into four different blocks namely the s- block, p- block, d- block and f- block. Lanthanides and actinides are found at the bottom of the periodic table.

Complete step by step solution:
The modern periodic table consists of 118 elements arranged in a total of eighteen groups and seven periods. The vertical columns represent the groups and the horizontal rows represent the periods. We know there are four different blocks in the periodic table. Each block corresponds to the filling of electrons in the corresponding orbital as mentioned in their name.
For example the f- block corresponds to the following of electrons in the f- orbital of the atoms. These elements make up the f- block. The f-block consists of two periods. The first period elements that correspond to the filling of 4f- orbital are known as lanthanoids while the second period elements in the f- block that correspond to the filling of 5f- orbitals are actinides. Collectively, both lanthanides and actinides are known as the f- block elements.
Hence, the correct option is C.

Note:
The modern periodic table is drawn and arranged according to the modern periodic law which proposes that the properties of all elements are the periodic functions of the number of protons present in their nucleus or the atomic numbers of the elements. Majority of the properties and behaviours of an element are decided by the electronic configuration of that element.