d-block elements

d-block elements

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Elements of d block :

The elements of III B, IV B, V B, VI B, VII B, VIII , VIII ,VIII , I B & II B groups are  present in the middle part of periodic table. Now a days these are elements of 3 to 12 group in the periodic table. In d-block elements last electron enters in (n-1)d orbital. These are also called transition elements.

There are 4 series of d-block elements.

3d-series: ₂₁Sc to ₃₀Zn ( Ist transition series i.e the last electron comes in 3d orbital)

4d-series: ₃₉ Y to ₄₈Cd ( II transition series i.e the last electrons comes in 4d orbital)

5d-series: ₅₇ La & ₇₂Hf to ₈₀Hg ( III transition series i.e the last electrons comes in 5d orbital)

6d-series: ₈₉Ac & ₁₀₄Rf – ₁₁₂Uub ( IV transition series  i.e the last electrons comes in 6d orbital )

General Characteristic of d-block elements :

1) Electronic configuration :

Electronic configuration of outermost shell is:

& penultimate shell is:

2) Variable valency : d-block elements show variable valency because electrons present in ns and (n-1)d take part in bond formation .

Valency of Cu is 1 &  2 [cuprous & cupric ]

Valency of Fe  is 2 & 3 [ferrous & ferric]

Valency of Au  is 1 & 3 [aurous & auric ]

3) Metallic nature : All d-block elements are metals.

4) formation of colored ions : Cations having incompletely  filled d-orbitals form colored ions.

Example:  Fe⁺⁺, Fe⁺⁺⁺, Cu⁺⁺, Ni⁺⁺ etc.

Cations having completely filled d-orbitals form colorless ions.

Example: Cu⁺, Ag⁺, Au⁺, Zn⁺⁺ etc.

5) Para & diamagnetic character : Atoms & ions containing unpaired electrons are paramagnetic.

Example: Fe, Fe⁺⁺, Fe⁺⁺⁺, Ni⁺⁺, Cu⁺⁺ etc.

Atoms & ions in which all the electrons are paired, are diamagnetic.

Example : Zn , Zn⁺⁺, Cu⁺, Ag⁺ etc.

6) Tendency to form complexes  : Transition metal cations form complexes due to small size of cation & presence of vacant d-orbitals of appropriate energy.

7) Catalytic property : Elements of d-block and their compounds are used as catalyst.

Example : Fe, Co, Ni, V₂O₅ , Fe₂O₃  ,Pt etc.

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