These small atoms enter into the void sites between the packed atoms of crystalline transition metals and form chemical bonds with transition metals. For Example, steel and cast iron become hard by forming interstitial compound with carbon.
The existence of vacant n — 1 d orbitals in transition elements and their ability to make bonds with trapped small atoms in the main cause of interstitial compound formation.
Other examples are : VH 0. Some borides of transition elements approach diamond in hardness. One of the main characteristic of a transition element is that it can show large variety of oxidation states in its compounds.
It is due to its characteristic electronic configuration i. The stability of oxidation state depends mainly on electronic configuration and also on the nature of other combining atom. The elements which show largest number of oxidation states occur in or near the middle of series i. The lesser number of oxidation states at extreme ends arise from either too few electrons to loose or share e. Sc and Ti or too many d electrons hence fewer orbitals available in which to share electrons with others for higher elements at upper end of first transition series i.
Thus electronic configuration, to large extent, the existence and stability of oxidation states. The other factors which determine stability of oxidation state are: i Enthalpy of atomisation ii Ionisation energy iii Enthalpy of solvation iv E.
In transition elements, there are greater horizontal similarities in the properties in contrast to the main group elements because of similar ns 2 common configuration of the outermost shell. This means that after scandium, d-orbitals become more stable than the s-orbital. In 2nd half of first row transition elements, electrons starts pairing up in 3d orbitals. A group of fourteen elements following lanthanum i. In these elements, the last electron enters the 4f-subshells pre pen ultimate shell.
It may be noted that atoms of these elements have electronic configuration with 6s 2 common but with variable occupancy of 4f level. These elements constitute one of the two series of inner transition elements or f-block. Lanthanoid contraction: In the lanthanoide series with the increase in atomic number, atomic radii and ionic radii decrease from one element to the other, but this decrease is very small. The regular small decrease in atomic radii and ionic radii of lanthanides with increasing atomic number along the series is called lanthanoid contraction.
Cause of lanthanoid contraction: When one moves from 58 Ce to 71 Lu along the lanthanide series nuclear charge goes on increasing by one unit every time. Simultaneously an electron is also added which enters to the inner f subshell. The shielding effect of f-orbitals in very poor due to their diffused shape.
It results in the stronger force of nuclear attraction of the 4f electrons and the outer electrons causing decrease in size. Consequences of lanthanoid contraction: i Similarly in the properties of elements of second and third transition series e. Get Android App. Get iOS App. Methyl orange is the example of which type of dye? Chemistry in Everyday Life. Enzymes with two sites are called Biomolecules.
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