Question

Give reason:
(i) Why do transition elements form Alloys?
(ii) What is the cause of Lanthanide contraction?

Answer 1

Hint:
(i) We know that the elements which are present in the d block of the periodic table are known as transition elements. They belong to group 3 to group 12.
(ii) Lanthanides, as we know, are those elements which are present in group 3. They are also known as rare earth metals.

Complete step-by-step answer:

(i) The atomic sizes of transition metals are very similar to each other. Therefore, these attributes to their nature of forming the alloys. As the atomic sizes are very similar one metal can replace the other metal from its lattice and form a solid solution which is the alloy. This is the reason why transition metals form homogeneous mixtures with one another in molten state.

(ii) Lanthanide contraction is defined as the gradual decrease in the atomic and ionic size of Lanthanide with an increase in their atomic number. The reason behind the Lanthanide contraction is because with an increase in the atomic number the positive charge on the nucleus increases by one unit and one more electron enters the same 4f subshell. The electrons in 4f subshell imperfectly shield each other. Shielding in 4f subshell is lesser than in a 5d subshell. With the increase in nuclear charge the valence shell is pulled slightly towards the nucleus. And thus the Lanthanide contraction occurs.

Note:
(i) There are 38 elements in the periodic table which fall under the category of the transition metals. As with all metals the transition elements are both ductile and malleable. They conduct electricity and heat. The interesting thing about the transition metal is that their valence electrons or rather the electrons that are used to combine with other elements are present in more than one shell. Which means that they often exhibit several common oxidation states. The three elements in the transition metals family which are Iron, Cobalt and Nickel are the only elements which are known to produce a magnetic field.
(ii) Poor shielding refers to the poor screening of nuclear charge. In other words, the nuclear charge is not effectively screened by electrons in question. The shielding effect of different orbitals is as follows:
 s orbitals >p orbitals > d orbitals > f orbitals