Electron Configuration For Chloride Ion

7.4: Electron Configurations of Ions

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Learning Objectives

Determine the electron configuration of ions
Justify the observed charge of ions to their electronic configuration
Define paramagnetism and diamagnetism
Justify the anomalies of the electron configurations in transition metals using magnetism experimental data

Electronic Configurations of Cations and Anions

The way we designate electronic configurations for cations and anions is essentially similar to that for neutral atoms in their ground state. That is, we follow the three important rules: Aufbau's Principle, Pauli-exclusion principle, and Hund's Rule. The electronic configuration of cations is assigned past removing electrons beginning in the outermost p orbital, followed by the s orbital and finally the d orbitals (if whatever more electrons need to exist removed). For instance, the basis country electronic configuration of calcium (Z=20) is 1s²2s²2p⁶3sⁱⁱ3p⁶4s². The calcium ion (Ca^two+), however, has two electrons less. Hence, the electron configuration for Ca²⁺ is 1s²2s^two2p^{half dozen}3s²3p⁶. Since we need to accept abroad 2 electrons, we first remove electrons from the outermost shell (northward=four). In this case, all the 4p subshells are empty; hence, we start by removing from the southward orbital, which is the 4s orbital. The electron configuration for Ca²⁺ is the same equally that for Argon, which has 18 electrons. Hence, we tin can say that both are isoelectronic, having the same of number of neutrons.

The electronic configuration of anions is assigned by adding electrons according to Aufbau's edifice up principle. Nosotros add electrons to fill the outermost orbital that is occupied, and then add together more electrons to the next college orbital. The neutral atom chlorine (Z=17), for instance has 17 electrons. Therefore, its footing state electronic configuration can be written as 1s^two2s²2p⁶3s^two3p⁵. The chloride ion (Cl^-), on the other hand, has an boosted electron for a total of 18 electrons. Following Aufbau'south principle, the electron occupies the partially filled 3p subshell beginning, making the 3p orbital completely filled. The electronic configuration for Cl^- can, therefore, be designated equally 1sⁱⁱ2s²2p^six3s²3p⁶. Once more, the electron configuration for the chloride ion is the same equally that for Ca²⁺ and Argon. Hence, they are all isoelectronic to each other.

Brining Information technology Total Circle

In Affiliate 2, we discussed the charges of ions formed for main group elements as the gaining or losing of electrons to obtain the same number of electrons as the nearest noble gas. At present, we can thoroughly empathise the reason for those charges using electron configurations. You have wondered why would calciumlose two electrons to form a Ca⁺²ion and be isoelectronic with Argon instead ofproceeds 6 electrons to become Ca^{-half dozen} and exist isoelectronic krypton. In terms of energetics, it takes much less energy to lose two electrons than to gain half dozen.

Past the same token, chlorine will be isoelectronic with Argon if it gains one electron, simply will take to lose seven electrons to exist isoelectronic with neon. That is why, we see the accuse of a chlorine ion as -ane, not +7.

The aforementioned dominion will apply to transition metals when forming ions. You should notation that thens electrons are always lost before the (n-i)d when forming cations for transition metals. For case,

the electron configuration for Zn: [Ar]4sⁱⁱ3d¹⁰

the electron configuration for Zn⁺²: [Ar]3d^ten

The transition metals still practise not end upwardly being isoelectronic with a noble gas, but the loss of two electrons is nonetheless beneficial due to achieving a more stable energy state for the organisation. Notwithstanding, how do we know that this is actually taking place and how do we trace what orbital(s) are losing/gaining electrons? We can report the magnetic properties of matter to help us tackle this problem.

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 management. An electron has an electron magnetic dipole moment, generated by the electron'due south intrinsic spin holding, making information technology an electric charge in motion. There are many different magnetic forms: including paramagnetism, and diamagnetism, ferromagnetism, and anti-ferromagnetism. Only paramagnetism, and diamagnetism are discussed here.

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's Rule states that electrons must occupy every orbital singly before whatever orbital is doubly occupied. This may leave the cantlet with many unpaired electrons. Because unpaired electrons can orient in either direction, they exhibit magnetic moments that tin can align with a magnet. This capability allows paramagnetic atoms to be attracted to magnetic fields. Diatomic oxygen, \(O_2\) is a skilful case of paramagnetism (that is best understood with molecular orbital theory). The post-obit video shows liquid oxygen attracted into a magnetic field created by a potent magnet

Video 9.half-dozen.1: A chemical demonstration of the paramagnetism of molecular oxygen, as shown by the attraction of liquid oxygen to magnets.

As shown in Video nine.6.one, since molecular oxygen (\(O_2\) is paramagnetic, it is attracted to the magnet. In dissimilarity, molecular nitrogen, \(N_2\), has no unpaired electrons and information technology is diamagnetic (discussed below); it is therefore unaffected past the magnet.

Note

Paramagnetism is a form of magnetism whereby materials are attracted by an externally practical magnetic field.

At that place are some exceptions to the paramagnetism rule; these concern some transition metals, in which the unpaired electron is not in a d-orbital. Examples of these metals include \(Sc^{iii+}\), \(Ti^{iv+}\), \(Zn^{2+}\), and \(Cu^+\).

For instance, you would expect the electron configuration of Cu to be: 1s²2s²2p⁶3s²3p^vi4s²3d^nine(paramagnetic, ane unpaired electron) and when it loses one electron to form the Cu⁺with the following electron configuration: 1s^two2s²2p⁶3s²3p⁶4s²3d⁸(paramagnetic; 2 unpaired electrons). In reality, the Cu⁺ion is non attracted to a magnetic field, indicating that it has no unpaired electrons. This explains the dissonant electron configuration of the transition metals and allows us to refine the electron configuration of Cu as: 1s²2s²2p⁶3s^two3p⁶4s¹3d^x (paramagnetic, 1 unpaired electron) and so becomes Cu⁺: 1s²2sⁱⁱ2p⁶3s²3p⁶3d^ten(diamagnetic; no unpaired electrons) so that nosotros are consistent with experimental information.

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 upwardly the same quantum country at the same fourth dimension, the electron spins are oriented in reverse directions. This causes the magnetic fields of the electrons to cancel out; thus there is no net magnetic moment, and the cantlet cannot exist attracted into a magnetic field. In fact, diamagnetic substances are weakly repelled past a magnetic field equally demonstrated with the pyrolytic carbon canvas in Effigy nine.6.i.

Figure 9.6.1: Levitating pyrolytic carbon: A small (~6 mm) piece of pyrolytic graphite levitating over a permanent neodymium magnet assortment (5 mm cubes on a piece of steel). Note that the poles of the magnets are aligned vertically and alternating (two with north facing upward, and ii with south facing up, diagonally). Paradigm used with permission from Wikipedia.

Note

Diamagnetic materials are repelled by the applied magnetic field.

Diamagnetism, to a greater or lesser degree, is a holding of all materials and ever makes a weak contribution to the material's response to a magnetic field. For materials that show some other course of magnetism (such paramagntism), the diamagnetic contribution becomes negligible.

How to tell if a substance is paramagnetic or diamagnetic

The magnetic form of a substance can be adamant 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:

Find the electron configuration
Draw the valence orbitals
Wait for unpaired electrons
Determine whether the substance is paramagnetic or diamagnetic

Case \(\PageIndex{i}\) : Chlorine Atoms

Pace 1: Find the electron configuration

For Cl atoms, the electron configuration is 3s^two3p^v

Step ii: Draw the valence orbitals

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

Step 3: Look for unpaired electrons

There is 1 unpaired electron.

Step four: Determine whether the substance is paramagnetic or diamagnetic

Since there is an unpaired electron, Cl atoms are paramagnetic (albeit, weakly).

Instance \(\PageIndex{2}\) : Zinc Atoms

Stride 1: Find the electron configuration

For Zn atoms, the electron configuration is 4s²3d¹⁰

Step 2: Depict the valence orbitals

Stride 3: Look for unpaired electrons

There are no unpaired electrons.

Step four: Determine whether the substance is paramagnetic or diamagnetic

Considering there are no unpaired electrons, Zn atoms are diamagnetic.

Exercise \(\PageIndex{1}\)

How many unpaired electrons are plant in oxygen atoms ?
How many unpaired electrons are found in bromine atoms?
Indicate whether boron atoms are paramagnetic or diamagnetic.
Indicate whether F^- ions are paramagnetic or diamagnetic.
Indicate whether Iron² ⁺ ions are paramagnetic or diamagnetic.

Answer (a):: The O atom has 2s²2p⁴ as the electron configuration. Therefore, O has 2 unpaired electrons.
Answer (b):: The Br atom has 4s^two3d¹⁰4p⁵ as the electron configuration. Therefore, Br has 1 unpaired electron.
Answer (c):: The B cantlet has 2s²2p^ane as the electron configuration. Because it has one unpaired electron, it is paramagnetic.
Respond (d):: The F^- ion has 2s²2p^half-dozen has the electron configuration. Considering it has no unpaired electrons, information technology is diamagnetic.
Answer (e):: The Atomic number 26² ⁺ ion has 3d⁶ has the electron configuration. Because it has 4 unpaired electrons, it is paramagnetic.