How Do You Know Which Elements Are Paramagnetic

ii.vii: Magnetic Properties of Atoms and Ions

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Learning Objectives

• To understand the difference between paramagnetism and diamagnetism

The magnetic moment of a system measures the strength and the direction of its magnetism. The term itself usually refers to the magnetic dipole moment. Anything that is magnetic, like a bar magnet or a loop of electric current, has a magnetic moment. A magnetic moment is a vector quantity, with a magnitude and a direction. An electron has an electron magnetic dipole moment, generated past the electron'due south intrinsic spin holding, making it an electrical accuse in motility. There are many different magnetic forms: including paramagnetism, and diamagnetism, ferromagnetism, and anti-ferromagnetism.

Paramagnetism

Paramagnetism refers to the magnetic state of an atom with one or more unpaired electrons. The unpaired electrons are attracted by a magnetic field due to the electrons' magnetic dipole moments. Hund'south Rule states that electrons must occupy every orbital singly before any orbital is doubly occupied. This may leave the cantlet with many unpaired electrons. Because unpaired electrons can spin in either direction, they brandish magnetic moments in any direction. This capability allows paramagnetic atoms to be attracted to magnetic fields. Diatomic oxygen, \(O_2\) is a good example of paramagnetism (described via molecular orbital theory). The post-obit video shows liquid oxygen attracted into a magnetic field created by a potent magnet:

Figure 2.vii.1: Equally shown in the video, molecular oxygen (\(O_2\) is paramagnetic and is attracted to the magnet. Incontrast, Molecular nitrogen, \(N_2\), however, has no unpaired electrons and it is diamagnetic (this concept is discussed below); it is therefore unaffected past the magnet.

At that place are some exceptions to the paramagnetism rule; these concern some transition metals, in which the unpaired electron is non in a d-orbital. Examples of these metals include \(Sc^{three+}\), \(Ti^{four+}\), \(Zn^{ii+}\), and \(Cu^+\). These metals are the non defined as paramagnetic: they are considered diamagnetic because all d-electrons are paired. Paramagnetic compounds sometimes display bulk magnetic properties due to the clustering of the metallic atoms. This phenomenon is known equally ferromagnetism, but this holding is not discussed here.

Diamagnetism

Diamagnetic substances are characterized by paired electrons—except in the previously-discussed case of transition metals, there are no unpaired electrons. According to the Pauli Exclusion Principle which states that no two identical electrons may take up the same breakthrough state at the same time, the electron spins are oriented in opposite directions. This causes the magnetic fields of the electrons to cancel out; thus at that place is no internet magnetic moment, and the cantlet cannot be attracted into a magnetic field. In fact, diamagnetic substances are weakly repelled past a magnetic field as demonstrated with the pyrolytic carbon sheet in Figure 2.7.2.

Figure 2.7.2: Levitating pyrolytic carbon: A small (~6mm) piece of pyrolytic graphite levitating over a permanent neodymium magnet assortment (5mm cubes on a piece of steel). Note that the poles of the magnets are aligned vertically and alternate (ii with north facing upwardly, and two with southward facing up, diagonally). from Wikipedia.

How to tell if a substance is paramagnetic or diamagnetic

The magnetic form of a substance tin can be determined by examining its electron configuration: if information technology shows unpaired electrons, and then the substance is paramagnetic; if all electrons are paired, the substance is diamagnetic. This process can be broken into four steps:

1. Find the electron configuration
2. Depict the valence orbitals
3. Look for unpaired electrons
4. Decide whether the substance is paramagnetic or diamagnetic

Example 2.7.ane: Chlorine Atoms

Step ane: Observe the electron configuration

For Cl atoms, the electron configuration is 3s^two3p⁵

Step 2: Draw the valence orbitals

Ignore the core electrons and focus on the valence electrons only.

Footstep 3: Look for unpaired electrons

There is 1 unpaired electron.

Step four: Determine whether the substance is paramagnetic or diamagnetic

Since at that place is an unpaired electron, Cl atoms are paramagnetic (albeit, weakly).

Instance 2.7.2: Zinc Atoms

Stride one: Find the electron configuration

For Zn atoms, the electron configuration is 4s^two3d^x

Step 2: Draw the valence orbitals

Pace 3: Expect for unpaired electrons

In that location are no unpaired electrons.

Footstep 4: Make up one's mind whether the substance is paramagnetic or diamagnetic

Because in that location are no unpaired electrons, Zn atoms are diamagnetic.

Exercise 2.7.1

1. How many unpaired electrons are found in oxygen atoms ?
2. How many unpaired electrons are found in bromine atoms?
3. Indicate whether boron atoms are paramagnetic or diamagnetic.
4. Indicate whether F^- ions are paramagnetic or diamagnetic.
5. Signal whether Iron^{2 +} ions are paramagnetic or diamagnetic.

Answer (a):

The O atom has 2s²2p⁴ as the electron configuration. Therefore, O has ii unpaired electrons.

Answer (b):

The Br atom has 4s²3d^ten4p⁵ as the electron configuration. Therefore, Br has 1 unpaired electron.

Answer (c):

The B atom has 2s²2p¹ every bit the electron configuration. Because it has one unpaired electron, it is paramagnetic.

Reply (d):

The F^- ion has 2s^two2p^half-dozen has the electron configuration. Because it has no unpaired electrons, it is diamagnetic.

Respond (e):

The Fe^{2 +} ion has 3d⁶ has the electron configuration. Because it has 4 unpaired electrons, it is paramagnetic.

References

1. Pettrucci, Ralph H. General Chemical science: Principles and Modern Applications. 9th. Upper Saddle River: Pearson Prentice Hall, 2007
2. Sherman, Alan, Sharon J. Sherman, and Leonard Russikoff. Basic Concepts of Chemistry 5th Edition. Boston, MA: Houghton Mifflin Company, 1992. Print.

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Source: https://chem.libretexts.org/Courses/Mount_Royal_University/Chem_1201/Unit_2._Periodic_Properties_of_the_Elements/2.07%3A_Magnetic_Properties_of_Atoms_and_Ions

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