Question

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

Answer 1

(i) Formation of alloy: It is the homogeneous mixture of two or more metals or metals with non-metals. Alloys are made to confer the property of metals. Transition elements have great tendency to form alloys because these elements have similar atomic size and can mutually substitute their positions in their crystal lattice. Alloys are comparatively hard and have higher m.p. than the elements form which they are made.
(ii) Reason: (1) The new electrons in lanthanides instead of going to outermost shell enters $(n-2)f$ suborbital as a result of which force of attraction increases between electron and nucleus due to which atom or ion contracts. (2) Electrons entering in $(n-2)f$ suborbital have negligible or zero shielding effect over electrons present in the last orbit. In addition the shape of $f$-suborbital is not favourable for the shielding effect of electrons. Thus lanthanide contraction occur.