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ChemistryEdu Logo d-block Elements | Atomic and Ionic Sizes#

Atomic and Ionic sizes of d-block elements#

  • In general, the atomic and ionic radius decreased in 3d series with increase in atomic number.

  • Reason: The new electron enters a d-orbital due to which nuclear charge increases. The shielding effect of a d-electron is not effective and hence the net electrostatic attraction between the nuclear charge and the outermost electron increases and the ionic radius decreases.

  • The 4d and 5d series elements exhibit similar radii due to lanthonoid contraction.

Lanthanoid contraction

It occurs because of the poorest shielding effect of f-electrons. Lanthanoid contraction is associated with the intervention of the 4f-orbitals which must be filled before the 5d-series of elements begin. The filling of 4f-orbitals before 5d-orbitals results in a regular decrease in atomic radii which essentially compensates for the expected increase in atomic size with increasing atomic number.

Atomic and ionic radii variation of 3d series

Density of d-block elements#

  • The decrease in metallic radius along with increase in atomic mass results in a general increase in density of these elements along the series.

Density

\[Sc < Ti < V < Zn < Cr < Mn < Fe < Co < Ni < Cu\]

Questions#

Zr belongs to 2nd d-series and Hf belongs to 3rd d-series but they have very similar physical and chemical properties. Why?

It is because they exhibit similar atomic radii due to lanthanoid contraction.

In the series from Ti (Z = 22) to Cu (Z = 29), copper has the highest density. Explain.

It is because density increases in the series due to decrease in atomic radius and increase in atomic mass.