Account for the following:
In case of transition elements, ions of the same charge in a given series show progressive decrease in radius with increasing atomic number.

Read the passage given below and answer the following questions: In transition elements, generally, ions of the same charge in a given series show progressive decrease in radius with increasing atomic number. This is because the new electron enters a d orbital each time the nuclear charge increases by unity. But the radii of the third (5d) series are virtually the same as those of the corresponding members of the second series. This phenomenon is associated with the intervention of the 4f orbitals which must be filled before the 5d series of elements begin. The filling of 4f before 5d orbital results in a regular decrease in atomic radii called Lanthanoid contraction. Following are the transition metal ions of 3d series: Ti^(4+), v^(2+), Mn^(3+), Cr^(3+) (Atomic number: Ti = 22, V = 23, Mn = 25, Cr = 24) Assertion (A): Ti^(4+) ion is colourless. Reason (R): All valence electrons are unpaired in Ti^(4+) ion.

Read the passage given below and answer the following questions: In transition elements, generally, ions of the same charge in a given series show progressive decrease in radius with increasing atomic number. This is because the new electron enters a d orbital each time the nuclear charge increases by unity. But the radii of the third (50) series are virtually the same as those of the corresponding members of the second series. This phenomenon is associated with the intervention of the 4f orbitals which must be filled before the 5d series of elements begin. The filling of 4f before 5d orbital results in a regular decrease in atomic radii called Lanthanoid contraction. Following are the transition metal ions of 3d series: Ti^(4+), V^(2+), Mn^(3+), Cr^(3+) (Atomic number: Ti = 22, V = 23, Mn = 25, Cr = 24) Assertion (A): Among the given ions, Mn^(3+) is the most strong oxidizing agent. Reason (R): Mn^(3+) has an unstable configuration.