The behaviour of lithium is similar to that of magnesium. This sort of similarity is commonly referred to as:

Correct option is D

The correct answer is (d) diagonal relationship.
The behavior of lithium (Li) is similar to that of magnesium (Mg) due to what is known as the diagonal relationship. In the periodic table, elements that are diagonally adjacent to each other often exhibit similarities in their chemical and physical properties. This occurs due to a balance between their atomic sizes and ionic charges, leading to comparable behavior despite being in different groups.
· Lithium (from Group 1) and Magnesium (from Group 2) are examples of this diagonal relationship. Both elements share similar properties such as:
· Formation of covalent compounds
· Low reactivity compared to other elements in their respective groups
· Formation of oxides and hydroxides that have low solubility in water
Information Booster:
● The diagonal relationship is primarily observed in the second and third periods of the periodic table. ● Other examples include beryllium (Be) and aluminum (Al), which also show similar behavior. ● This phenomenon arises because of a balance between ionic radii and charge density. ● The diagonal relationship helps predict similarities in properties that are not apparent from the group trends alone.