Chapter 3, Problem 3.1KSP

Interpretation Introduction

Interpretation:

The noble gas core for $\text{Mo}$ should be identified using the concept of electron configuration.

Concept Introduction:

An orbital is an area of space in which electrons are orderly filled.  The maximum capacity in any type of orbital is two electrons.  An atomic orbital is defined as the region of space in which the probability of finding the electrons is highest.  It is subdivided into four orbitals such as $s,p,dandf$ orbitals which depend upon the number of electrons present in the nucleus of a particular atom.

There are three basic principles in which orbitals are filled by the electrons.

1. 1. Aufbau principle: In German, the word 'aufbau' means 'building up'.  The electrons are arranged in various orbitals in the order of increasing energies.
2. 2. Pauli exclusion principle: An electron does not have all the four quantum numbers.
3. 3. Hund’s rule: Each orbital is singly engaged with one electron having the maximum same spin capacity after that only pairing occurs.

The electron configuration is the allocation of electrons of an atom in atomic orbitals.  Electronic configuration of a particular atom is written by following the three basic principles.

To identify: Identify the noble gas core for $\text{Mo}$

Answer to Problem 3.1KSP

The noble gas core for $\text{Mo}$ is (b) $\text{Kr}$

Explanation of Solution

Reason for correct option

$\text{Mo}$ is present in VIB group of the periodic table.  Its atomic number is 42.  Its outermost electron configuration is $\left[\text{Kr}\right]4d^{5}5s^1$.  It is present in 5^th row of the periodic table.  Hence the noble gas core for $\text{Mo}$ should be present in 4^th row of the periodic table which is krypton $\left(\text{Kr-36}\right)$.

Therefore, option (b) is correct.

Reasons for incorrect options:

$\text{Ar}$ is present in 3^th row of the periodic table whereas $\text{Mo}$ is present in 5^th row of the periodic table.  Hence, $\text{Ar}$ is lesser noble gas core for $\text{Mo}$.  $\text{Xe}$ is present in 5^th row of the periodic table.  Hence, $\text{Xe}$ is greater noble gas core for $\text{Mo}$.  $\text{Ne}$ is present in 2^th row of the periodic table whereas $\text{Mo}$ is present in 5^th row of the periodic table.  Hence, $\text{Ne}$ is lesser noble gas core for $\text{Mo}$.  $\text{Rn}$ is present in 6^th row of the periodic table whereas $\text{Mo}$ is present in 5^th row of the periodic table.  Hence, $\text{Rn}$ is greater noble gas core for $\text{Mo}$.

Therefore, the options (a), (c), (d) and (e) are incorrect.

Conclusion

The noble gas core for $\text{Mo}$ is identified using the concept of electron configuration.