Question

Discuss the position of d-block elements, lanthanoids and actinoids in the periodic table.

Answer 1

• Position of d-block elements in the modern periodic table:

1. The transition elements are placed in the periods 4 to 7 and groups 3 to 12.
2. They constitute 3d, 4d, 5d and 6d series.
3. They are placed at the centre with s block on one side and p block on the other side.
4. The electropositivity, reactivity and other properties show a gradual change from s block to p block through those of the d block elements.

• Position of lanthanoids and actinoids in the modern periodic table:

1. Lanthanoids and actinoids are placed separately at the bottom of the periodic table. They are a subset of 6th and 7th periods.
2. These elements have 1 to 14 electrons in their f orbital, 0 or 1 in the penultimate energy level and 2 electrons in the outermost orbital.