Lanthanoids are (a) 14 elements in the sixth period (atomic no. = 58 to 71) that are filling 4f sublevel Lanthanoids are (a) 14 elements in the sixth period (atomic no. = 58 to 71) that are filling 4f sublevel November 29, 2020 Category: Uncategorised (JEE Advanced Physics by BM Sharma + GMP Solutions) ,