Question

Transition metals are not characterized by:
A.Fixed valency
B.coloured compound
C.high melting and boiling points
D.tendency to form complexes

Answer 1

"An element whose atom has a partly filled d subshell, or which can give birth to cations with an incomplete d subshell," according to the IUPAC definition. Any element in the d-block of the periodic table, which covers groups 3 to 12, is referred to as a "transition metal" by many scientists. The f-block lanthanide and actinide series are also considered transition metals and are referred to as "inner transition metals" in practise.

Complete answer:
An element's valency is its ability to combine with other elements. The valency of an element is the amount of electrons supplied or received by an atom in order for it to have the electronic configuration of the closest noble gas. The valency of the same element fluctuates as a result of the varied circumstances under which a chemical reaction occurs. As a result, metals such as lead, tin, copper, mercury, iron, and others have varying valency. Metals donate electrons from their valence shell to produce positively charged ions in most cases. Some metals, on the other hand, lose electrons from the shell next to the valence shell. The element has more than one electropositive valency in this circumstance. Variable valency is a term used to describe such things.
The majority of the elements in the III A group have a +3 oxidation state. However, as we move down the group, the oxidation state +1 becomes more prominent. Similarly, the elements in the IV A group have a +4 oxidation state in general, but the +2 state becomes more apparent as we move down the group. The two s electrons ($n{{s}^{2}}$) in the valence shell are usually inactive and do not participate in bond formation. This is referred to as the inert pair effect. As a result, fluctuating valency in p block elements is mostly caused by the inert pair effect.

Hence option a is correct.

Note:
The number of electrons lost or acquired by an element's atom during the creation of ionic bonds is its electrovalency. Variable valency is not displayed in the s-block elements. P-block elements with higher atomic numbers and inner transition elements, on the other hand, have variable valency.