14 elements in the sixth period (atomic no. 90 to 103) that are filling 4f sublevel
14 elements in the seventh period (atomic number = 90 to 103) that are filling 5f sublevel
14 elements in the sixth period (atomic number = 58 to 71) that are filling the 4f sublevel
14 elements in the seventh period (atomic number = 50 to 71) that are filling 4f sublevel.
