d And f-Block Elements

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The Transition Elements (d- block)

1. The elements that lie in between s-block and p-block are called as the d-block elements.

2. The transition metals are studied in 4 horizontal series corresponding to filling of the sublevels of 3d (Sc to Zn), 4d (Y to Cd), 5d (La to Hg, omitting Ce to Lu) and 6d (Ac onwards but incomplete) series, in the 4^th, 5^th, 6^th and 7^thperiods.

3. The d-block elements are known as transition elements because these elements possess properties that are transitional between the s- and p-block elements in the modern periodic table.

4. The general electronic configuration of d-block elements is (n-1)d^1-10ns^1-2.

The Inner Transition Elements (f-Block)

The elements in which the last electron enters the f-orbital of their atoms are called f-block elements. In these elements, the last electron is added to the third outermost (called antepenultimate) energy level, (n-2)f. They consist of elements comprising the lanthanide series and actinide series both groups being placed at the bottom of the periodic table. These elements are also called inner transition elements. The two series are generated by the filling of characteristic electrons in the 4f- and 5f-orbitals.

The lanthanide series (Ln series) comprises of fourteen elements starting with cerium Ce (Z = 58) and ending with lutetium Lu (Z = 71). They are called lanthanides as they involve the filling of 4f-orbitals following lanthanum (Z=57). The actinide series also consists of 14 elements, starting from actinium, Ac (Z = 89) with which these elements closely resemble, and include the elements from thorium, Th (Z = 90) to lawrencium, Lw (Z = 103). They are called actinides, as the series involves the filling of 5f-orbitals. These elements occur very rarely and are therefore, also known as rare earth elements.

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