One of the most striking feature of transition element is to show the variable oxidation state. The oxidation state shown by the transition element may be related to their electronic configuration. The outermost electronic configuration of transition element is (n-1)d and ns orbital are quite close to each other hence both are ns (ultimate cell) and (n-1)d (penultimate cell) electrons are available for bonding purpose.
Scandium has +2 oxidation number if both the electrons are used in s orbitals and +3 when 2 s electrons and 1 d electrons are used.
Many iconic and covalent compounds of transition element are colored . In contrasts, compounds of s, np block elements are always colorless because the require high energy to excite so only light of uv region are suitable for them. If absorption of light occur in the visible region of spectrum the transmitted light is colored with the complementary color of the light absorb.
All d orbitals of an isolated atom of transition element are of same energy (degenerate) this degenerated -orbitals of the central metal atom splits into two different energy level the difference between two energy level depends upon the nature of combining atoms or ion. When any ion or molecule approaches the metal ion, the d orbitals splits into two sets i.e t2g and eg.
The color of transition metal complexes are due to transition of unpaired electron from one energy level to another energy level i.e from one d orbital to another d this phenomenon is called d1d transition.
If any configuration of any transition element compounds is (n-1) d1-9 then they are generally colored. On the other hand the transition metal ion having completely filled d-orbital (d10) or empty d-orbital (d0) are colorless or white .
Factor of affecting color of complexes
- Change in number of d electrons.
- Filled strength of the ligand.
- Geometry of the complex
On the basis of the magnetic field the substance are classified into three types i.e diamagnetic , paramagnetic and ferromagnetic.
The substance which are attracted by the magnetic field called paramagnetic and substance which repelled by magnetic field called diamagnetic. The transition element which contains a unpaired electron then its shows paramagnetic property but if it contains a paired electron then its shows diamagnetic properties when number of unpaired electron is increased then paramagnetic properties also increase.
A moving electron is a micromagnet when the transition element having unpaired electron placed in the magnetic field then it produces a magnetic moment which is sufficient to overcome a magnetic moment produces by the applied magnetic field. Consequently, it experiences attractive force and shows paramagnetic property.
The transition elements have an unparallel tendency to form coordination with groups which are able to donate electron pair these groups are called ligands. A ligand may be a neutral molecules such as NH3, H2o etc. The ability of transition metal cation to form complexes id due to following regions:
- The transitions metal cations are relatively very small in size and hence they have high positive charge density which makes them easy to accept the lone pair of electron donate by ligands.
- These cations have vacant d-orbital which are capable of receiving lone pair of electron donated by ligands.
- The transitions metals are capable of showing variables oxidation states.
An alloy is define as the solid solution containing two or more different elements at least one of them is metal.
Types of alloy
- Interstitial alloy in which atoms of small size molecules like hydrogen, Boron etc. get entrapped in both the interstitial space of transition metal eg: steel =Fe + c.
- Solid solution alloy:
These are formed when one or more transition metal are added to iron Eg: stainless steel.
Transition metal can be form alloy very easily because the size of transition metal quite similar and they can be mutually substitute one another in a crystal lattice. Consequently molten transition metal are mutually miscible to one and another and when a mixture of their solution is cooled by alloy form.