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Q.1 : What is the significance of half-filled and fully-filled orbitals in atomic structure?
Ans. Half-filled and fully-filled orbitals exhibit extra stability due to favourable exchange energy and symmetrical distribution of electrons. This stability influences the electronic configurations of certain elements and contributes to their unique properties.
Q.2 : How do paramagnetism and diamagnetism differ from each other?
Ans. Paramagnetism is a phenomenon where certain materials are weakly attracted to an external magnetic field due to the presence of unpaired electrons, while diamagnetism is a phenomenon where materials are weakly repelled by an applied magnetic field due to the induction of a magnetic field in the opposite direction.
Q.3 : What causes paramagnetism and diamagnetism in materials?
Ans. Paramagnetism arises from the alignment of magnetic moments of unpaired electrons parallel to an external magnetic field, while diamagnetism results from the induction of a magnetic field in the opposite direction to an applied magnetic field due to the orbital motion of electrons.
Q.4 : What is spin magnetic moment, and how does it contribute to the magnetic behaviour of atoms?
Ans. Spin magnetic moment is a property of electrons arising from their intrinsic spin. It contributes to the overall magnetic behaviour of atoms by adding up the magnetic moments of all the electrons within the atom.
Stability Of Orbitals, Paramagnetism, Diamagnetism And Spin Magnetic Moment
Stability Of Orbitals : stability of orbitals in chemistry is determined by factors such as the effective nuclear charge, electron-electron repulsion, and the arrangement of electrons according to the Aufbau principle, Hund's rule, and the Pauli exclusion principle. Stable orbitals minimize energy and maximize electron density distribution.
Shrivastav 3 Jun, 2024
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Stability Of Orbitals :
Welcome, curious minds, to the fascinating realm of atomic structure! In the microscopic world of atoms, electrons play a crucial role in determining an element's properties. However, certain configurations of electrons exhibit extraordinary stability, leading to intriguing phenomena like paramagnetism and diamagnetism. In this article, we'll explore the concepts of extra stability associated with half-filled and fully-filled orbitals, as well as the intriguing behaviours of paramagnetism, diamagnetism, and spin magnetic moment. By the end of our exploration, you'll have a deeper understanding of these concepts and their significance in chemistry.
Stability Of Orbitals : Extra stability of Half-filled and fully-filled orbitals
Extra stability of Half-filled and fully-filled orbitals :
The electronic configuration of most of the atoms follows the Aufbau’s rule. However, in certain elements such as Cr, Cu, etc. Where the two subshells (4s) and 3d) differ slightly in their energies (4s < 3d), an electron shifts from a subshell of lower energy (4s) to a subshell of higher energy (3d), provided such a shift results in all orbitals of the subshell of higher energy getting either completely filled or half-filled.
and not
and not
It has been found that there is extra stability associated with these electronic configuration. This stabilization is due to the following two factors.
(i)
Symmetrical distribution of electron:
It is well known that symmetry leads to stability. The completely filled or half-filled subshell have symmetrical distribution of electron in them and are therefore more stable. This effect is more dominant in d and f-orbitals. This means three or six electrons in p-subshell, 4 or 10 electrons in d-subshell and 7 or 14 in f-subshell forms a stable arrangement.
(ii)
Exchange energy :
This stabilizing effect arises wherever two or more electrons with the same spin are present in the degenerate orbitals of a subshell. These electrons tend to exchange their positions and the energy released due to this exchange is called exchange energy. The number of exchanges that can take place is maximum when the subshell is either half filled or fully filled. As result the exchange energy is maximum and so the stability increases.
Total exchange pairs = 10
n → Number of electron with parallel spins.
●
In atoms, when an orbital is exactly half-filled, it results in a more stable configuration due to the symmetry and favourable exchange energy associated with the electron spin.
●
Understanding the extra stability of half-filled orbitals helps explain the anomalous electronic configurations of certain elements and their unique properties.
Paramagnetism
(i)
The substances which are weakly attracted by magnetic field are paramagnetic and this phenomenon is known as paramagnetism.
(ii)
Their magnetic character is retained till they are in magnetic field and lose their magnetism when removed from magnetic field.
Diamagnetism
(i)
The substances which are weakly repelled by magnetic field are diamagnetic and this phenomenon is known as diamagnetism.
(ii)
Diamagnetic substances lack unpaired electrons and their magnetic moment is zero e.g., NaCl, N
2
O
4
etc.
Spin Magnetic moment
The spin magnetic moment of electron (excluding orbit magnetic moment) is given by :
Where n is number of unpaired electron in species.
The magnetic moment is expressed in Bohr magneton (B.M.)
Q1.
A compound of vanadium has magnetic moment of 1.73 BM. Find out the electronic configuration of vanadium ion in the compound.
Ans.
Vanadium belongs to 3d series with Z = 23. The magnetic moment of 3d series metal is given by spin only formula.
n = 1
Magnetic moment correspond to one unpaired electron.
Electronic configuration of vanadium atom
For one unpaired electron 4 electron must be removed in which first 2 electron are lost from 4s orbital (outermost), and the remaining electron 4 electron must be removed from 3d (inner shell).
Electronic configuration of V
+4
.
1s
2
, 2s
2
, 2p
6
3s
2
3p
6
4s
0
3d
1
Q2.
Calculate total spin, magnetic moment for the atoms having at no. 7, 24 and 36.
