Question

What is lanthanide and actinide series?

Answer 1

i. Lanthanide series: The fourteen elements after lanthanum (Z = 57) i.e., from cerium (Z = 58) to lutetium (Z = 71) are named after their preceding member (₅₇La) present in the third group and 6^th period and are called lanthanides. They are kept in separate series called lanthanide series at the bottom of the modem periodic table.

ii. Actinide series: The fourteen elements after actinium i.e., from thorium (Z = 90) to lawrencium (Z = 103) are named after ₈₉Ac present in third period and 7^th group. They are kept in separate series called actinide series at the bottom of the modem periodic table.

Answer 2

The lanthanide and actinide series make up the inner transition metals. The lanthanide series includes elements 58 to 71, which fill their 4f sublevel progressively. The actinides are elements 89 to 103 and fill their 5f sublevel progressively.