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Q.1 : What is Hund's Rule, and why is it important in chemistry?
Ans. Hund's Rule states that electrons prefer to occupy degenerate orbitals singly before pairing up with opposite spins. It is important in chemistry because it influences the arrangement of electrons within atoms.
Q.2 : How does Hund's Rule contribute to the stability of atoms?
Ans. Hund's Rule maximizes the total electron spin within an atom, leading to greater stability. By filling degenerate orbitals with parallel spins before pairing up, atoms achieve a lower energy state, making them more stable.
Q.3 : What is Pauli's Exclusion Principle, and why is it significant in atomic theory?
Ans. Pauli's Exclusion Principle states that no two electrons in an atom can have the same set of quantum numbers. It is significant in atomic theory because it ensures that electrons within an atom occupy unique positions in atomic orbitals, contributing to the stability and integrity of the atom's electronic structure.
Q.4 : How does Pauli's Exclusion Principle influence the electronic configuration of atoms?
Ans. Pauli's Exclusion Principle dictates that each orbital within an atom can hold a maximum of two electrons with opposite spins. This principle guides the arrangement of electrons within atomic orbitals, ensuring that each electron occupies a unique position based on its quantum numbers.
Q.5 : Are there any real-world applications of Hund's Rule and Pauli's Exclusion Principle?
Ans. Yes, both Hund's Rule and Pauli's Exclusion Principle have real-world applications in various fields such as chemistry, materials science, and electronics. They are fundamental principles that govern the behaviour of electrons within atoms, influencing chemical reactivity & material properties.
Hund's Maximum Multiplicity Rule And Pauli's Exclusion Principle , Important Topics For JEE 2025
Hund's Maximum Multiplicity Rule : Understand Hund's Maximum Multiplicity Rule, a key principle in atomic chemistry. It states that electrons fill degenerate orbitals singly and with parallel spins before pairing up. This minimizes electron repulsion and maximizes total spin, influencing the electronic configuration and stability of atoms.
Shrivastav 2 Jun, 2024
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Hund's Maximum Multiplicity Rule :
Welcome, young scientists, to the intriguing world of electronic configuration rules! As we journey through the microscopic realm of atoms, understanding how electrons are arranged within them is crucial. In this article, we'll delve into two fundamental principles governing electron behaviour: Hund's Maximum Multiplicity Rule and Pauli's Exclusion Principle. By unravelling these rules, you'll gain valuable insights into the behaviour of electrons and the structure of atoms.
Before we delve into the specifics of Hund's Rule and Pauli's Principle, let's grasp the concept of electronic configuration. Electronic configuration refers to the arrangement of electrons within an atom's electron shells and subshells. These configurations follow specific rules that dictate how electrons occupy various orbitals around the nucleus.
Hund's Maximum Multiplicity Rule
Hund's Maximum Multiplicity Rule :
Hund's Rule, named after German physicist Friedrich Hund, states that electrons occupy degenerate orbitals (orbitals with the same energy) singly before pairing up. In simpler terms, electrons prefer to occupy empty orbitals within the same subshell with parallel spins (spin-up) rather than pairing with opposite spins (spin-down) until necessary.
This rule deals with the filling of electrons into the orbitals belonging to the same subshell (that is, orbitals of equal energy, called degenerate orbitals).
It states,
pairing of electrons in the orbitals belonging to the same subshell (p, d or f) does not take place until each orbital belonging to that subshell has got one electron each i.e., it is singly occupied.
Since there are three p, five d and seven f orbitals, therefore, the pairing of electrons will start in the p, d and f orbitals with the entry of 4
th
, 6
th
and 8
th
electron, respectively.
(ii)
26
Fe → 1s
2
, 2s
2
, 2p
6
, 3s
2
, 3p
6
, 4s
2
3d
6
Or
[Ar] 4s
2
, 3d
6
No. of unpaired electrons = 4
∴
Total spin
(iii)
10
Ne → 1s
2
, 2s
2
2p
6
No. of unpaired electrons = 0
Total spin = 0
Pauli's Exclusion Principle
Pauli's Exclusion Principle :
Pauli's Exclusion Principle, formulated by Austrian physicist Wolfgang Pauli, states that
no two electrons in an atom can have the same set of quantum numbers
. Specifically, it prohibits two electrons within the same atom from having identical values for all four quantum numbers: principal quantum number (n), azimuthal quantum number (l), magnetic quantum number (m), and spin quantum number (s). This principle ensures that each orbital can hold a maximum of two electrons with opposite spins.
i.e. an orbital can accommodate maximum 2 electrons with opposite spin.
Ex.1.
→
1s
2
2s
2
2p
2
n
=
1
1
2
l
=
0
0
1
m
=
0
0
+1, 0, –1
s
=
Ex.2.
17
Cl
→
1s
2
2s
2
2p
6
3s
2
3p
5
n
=
1
2
2
3
3
l
=
0
0
1
0
1
m
=
0
0
+1, –1, 0
0
+1, –1, 0
s
=
Pauli's Exclusion Principle dictates that no two electrons in an atom can have identical sets of quantum numbers. This principle ensures that each electron within an atom is uniquely defined by its quantum numbers, preventing electron overlap and ensuring the stability and integrity of the atom's electronic configuration. As a result, each orbital can accommodate a maximum of two electrons with opposite spins, contributing to the overall stability of the atom.
Configuration of Ion
(a)
First we have to write the configuration of atom in its ground state.
(b)
Now, based upon the charge present on the atom we have to remove or add electron in its valence shell.
