Question

Which of the following is false?
(This question has multiple correct options)
a.) $C{r^{2 + }}\left( g \right)$ ion has greater magnetic moment compared to $C{o^{3 + }}\left( g \right)$ .
b.) The magnitude of ionization potential of iron-an ion (monoanion) would be equal to electron gain enthalpy of iron.
c.) Lanthanide contraction is the cause of lower I.P of $Pb$ than $Sn$ .
d.) If successive ionization energies are 332, 738, 849, 4080, 4958 (in kJ/mol). Then this element can be of 15th group.

Answer 1

Hint: In the given problem all the four options are independent and not related to each other. In order to find the false statements among the given ones we have to go through the statements one by one and to understand the basic definition of each one of them further on the basis of proper explanation for each one of them we will find the false statements as well as the correct substitutes in their place for the given options.

Complete step by step answer:
Statement A.
$C{r^{2 + }}\left( g \right)$ ion has greater magnetic moment compared to $C{o^{3 + }}\left( g \right)$ .
Let us understand the magnetic moment first.
The magnetic moment of a compound is the magnetic intensity and orientation of a magnet or other magnetic field generating entity. An object's magnetic dipole moment is conveniently defined in terms of the torque encountered by the object in a given magnetic field.
In the given case we have to compare the magnetic moment of two ions. As we know that the magnetic moment of an ion depends upon the number of unpaired electrons in the ions. The magnetic moment of an ion is directly proportional to the number of unpaired electrons.
As we know that $C{r^{2 + }}\left( g \right)$ ion has 4 unpaired electrons whereas the $C{o^{3 + }}\left( g \right)$ ion has 6 unpaired electrons so we can infer that the magnetic moment of $C{o^{3 + }}\left( g \right)$ ion is greater than the magnetic moment of $C{r^{2 + }}\left( g \right)$ ion.
So, statement A is false.

Statement D.
If successive ionization energies are 332, 738, 849, 4080, 4958 (in kJ/mol). Then this element can be of 15th group.
We have the successive ionization energy for any unknown compound and we need to find the group to which it belongs.
We know that the group to which an element belongs depends upon the number of valence electrons that the element possesses. So in order to find the group let us find the number of valence electrons on the basis of ionization energy.
As we can see that the ionization energy of 1st, 2nd and 3rd electron is increasing but is something normal but as we move from 3rd to 4th electron ionization energy has increased to around 5 times which is quite high. This means that the 4th valence electron is absent and the electron is removed from the inner layer. So there are only 3 electrons present in the element.
As there are 3 valence electrons, so the element belongs to the 13th group and not from 15the group.
So, statement D is also false.
Whereas the statements B and C are true.
So, the correct answer is “Option A and D”.

Note: In order to solve the given problems students must know the basic definitions which are involved in the problems. Students must know the concept of ionization and valence electrons in order to solve the problems related to statement D in the problems. Valence electrons are the electrons which are present in the outermost layer of the atom of the element.