Question

The basic character of the transition metal monoxides follows the order:
(Atomic number ${\text{Ti = 22,V = 23,Cr = 24,Fe = 26}}$ )
A. $TiO > FeO > VO > CrO$
B. $TiO > VO > CrO > FeO$
C. $TiO > CrO > VO > FeO$
D. $CrO > VO > FeO > TiO$

Answer 1

Hint: Transition metals are d-block elements whose last electron goes to the d orbital and Basic character of any compound can be calculated by the ability of donation of lone pair of electron to the other substance and this type of base is known as lewis base.

Step by step answer: Given elements belong to the 1st series of the transition metal, which are known as 3d series because the last electron goes to the d subshell of 3rd orbital. Some points regarding this series is as follow:

As we move from left side to right side in the first transition series atomic number of elements increases and no. of electrons also increases.

Size of elements on moving left to right decreases because effective nuclear charge of nucleus on the outermost shell electron increases.

It means electronegativity of atoms increases from left to right, then the power of donation of electrons decreases which means the basicity of that element decreases.

So, the correct order of basicity of the transition metal monoxides is $TiO > VO > CrO > FeO$ i.e. option (B) is correct.

Note: In this question you may get confused on the order of size of elements in the series, because order of size of elements is not regular in the periods and groups. In periods of increasing atomic number size decreases and on the groups with the increase of atomic number size also increases.