Lanthanides are

Options

A. 14 elements in the sixth period (At.no=90 to 103) that are filling 4f sub-level
B. 14 elements in the seventh period (At.no.=90 to 103) that are filling 5f sub-level
C. 14 elements in the sixth period (At.no.=58 to 171) that are filling 4f sub-level).
D. 14 elements in the seventh period (At. No.=58 to 71) that are filling 4f sub-level

Answer

C

Explanation

Lanthanides are the 14 elements of IIIB group and sixth period (at no. =58 to 71) that are filling sub-shell of antipenultimate shell from 1 to 14. Actually, they are placed below the periodic table horizontal row as lanthanide series.