F block elements are divided into two series, namely lanthanoids and actinoids. This block of elements is often referred to as inner transition metals because they provide a transition in the 6th and 7th row of the periodic table which separates the s block and the d block elements. Elements whose f orbital getting filled up by electrons are called f block elements. These elements have electrons, (1 to 14) in the f orbital, (0 to 1) in the d orbital of the penultimate energy level and in the outermost orbital. There are two series in the f block corresponding to the filling up of 4f and 5f orbitals. The elements are 4f series of Ce to Lu and 5f series of Th to Lw. There are 14 elements filling up the ‘f’ orbital in each series. Classification of F Block Elements The elements belonging to the f block are further differentiated into: The first series of elements are called lanthanides and include elements with atomic numbers beginning from 57 and ending at 71. These elements are non-radioactive (except for promethium, which is radioactive) The second series of elements are called actinides and include elements with atomic numbers beginning from 89 and ending at 103. These elements generally have a radioactive nature. The list of all the f block elements is provided below. The row beginning with Lanthanum is the row containing all the lanthanides whereas the row beginning with Actinium is the row that contains all the actinides. F block Elements as Inner Transition Elements Since the f orbital lies much inside than d orbital, in relation to the transition metals naming, f block elements are called inner transition elements. Properties of F block Elements Have electrons added to the ‘f’ sub-orbitals of (n-2) level Are placed between (n-1)d and ns block elements in the periodic table. Properties are similar to d-block elements.

Ridhi Kumari

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