Electron Gain Enthalpy of Elements in Modern Periodic Table

Introduction

The quantity of energy released or absorbed when a neutral isolated gaseous atom absorbs an $\mathrm{e^{-}}$ to create a negatively charged anion is described as electron gain enthalpy. When the $\mathrm{e^{-}}$ joins with the isolated gaseous atom, energy can be produced or absorbed, depending on whether the process is exothermic or endothermic. The greater the energy released during the mixing process, the greater the electron gain enthalpy, indicated as 𝛥𝐻𝑒𝑔.

$$\mathrm{X(g)\:+\:e^{-}\rightarrow\:X^{-}(g)}$$

Normally, exothermic processes occur, resulting in a negative electron gain enthalpy. Because halogens only require one atom to achieve the noble gas configuration, they have a substantially negative electron gain enthalpy, in contrast to noble gases, which have a strongly positive $\mathrm{e^{-}}$ gain enthalpy.

What is Electron Gain Enthalpy of Elements?

It is the quantity of energy produced when an $\mathrm{e^{-}}$ is supplied to an isolated gaseous atom. The 𝑒− gain enthalpy is expressed in KJ/mol or $\mathrm{e^{-}}$ volts per atom. The reaction can be exothermic or endothermic based on the constituent variables.

When an $\mathrm{e^{-}}$ is introduced to a gaseous atom that has already obtained an $\mathrm{e^{-}}$ as well as has accomplished the stable noble gas configuration, or when electrons are introduced to noble gases, a significant quantity of additional energy is needed to conquer the repulsive forces caused by the already existing electrons in the orbitals. As a result, the electron gain enthalpy becomes extremely positive in this scenario. Halogens have substantially negative electron gain enthalpies. These two instances demonstrate that until the noble gases, there will be substantial negative values to the top right of the periodic chart.

Factors That Affect Electron Gain Enthalpy

The nuclear charge

When the overall negative charge grows, the force of attraction increases with the additional electron. Furthermore, when the size of the nucleus rises, the enthalpy turns more negative.

Atomic weight

The distance between the final cell as well as the nucleus grows as the atomic size grows. As a result, the force of attraction between the new $\mathrm{e^{-}}$ & the core weakens. As a result, it becomes less negative.

Electronic Configuration

Only elements with partly or fully-filled orbitals have higher stability. When energy is applied to certain elements, electrons are added to them. As a result, their $\mathrm{e^{-}}$ gain enthalpy value is higher.

Electron Gain Enthalpy in Period

The atomic size of elements decreases while the effective nuclear charge grows as one advances from the left side to the right side through time. Hence, the force of attraction between the nucleus and the extra 𝑒− increases. Therefore, the electron gain enthalpy becomes more -ve as the period proceeds from the left side to the right side.

Electron Gain Enthalpy Group

As $\mathrm{e^{-}}$ moves down in a group, it gets less negative. This is because both atomic sizes. as well as nuclear charge, grow, but atomic size has a greater influence than nuclear charge. As a result, the attraction between the nucleus & the additional $\mathrm{e^{-}}$ lessens, & the enthalpy becomes less -ve.

Measurement and Use of Electron Affinity

Because their energy levels can be changed by interacting with other atoms or molecules in a solid or liquid state, this property is only used to identify atoms as well as molecules in a gaseous state. Robert S. Mulliken devised an electronegativity scale for atoms based on a list of electron affinities, which is comparable to the sum of electron affinity & ionisation potential. Two further theoretical concepts involving $\mathrm{e^{-}}$ affinity are electronic chemical potential as well as chemical hardness. Another example is that an $\mathrm{e^{-}}$ acceptor is a molecule or atom that has a higher positive value of electron affinity than another. An $\mathrm{e^{-}}$ donor is someone who has a lower positive value. When they are brought together, charge transfer processes may occur.

One-Electron Reduction

A single $\mathrm{e^{-}}$ atom is transferred from a donor chemical to an organic substance. It distinguishes two $\mathrm{e^{-}}$ organic reductions like hydride transfer processes. A radical anion is frequently formed as the 1𝑠𝑡 step in a 1 $\mathrm{e^{-}}$ reduction, and it then engages in later reactions. The secondary process in the Birch reduction is proton elimination from alcohol. This is also referred to as a dissolving metal reduction process. In liquid ammonia or sodium systems, alkyne reduction to an alkene works similarly. The initial radical anion intermediate extracts an ammonia proton as well as transfers it to the free radical. To create the anion, a 2𝑛𝑑 one $\mathrm{e^{-}}$ transfer is needed, which additionally takes a proton from the neutral alkene.

Conclusion

The quantity of energy liberated when an $\mathrm{e^{-}}$ is introduced to an isolated gaseous system referred to as electron gain enthalpy. KJ/mol is the unit of electron gain enthalpy. An element's electron gain enthalpy is determined by its nuclear charge, atomic radius, as well as electronic configuration. As one moves down in a group, the 𝑒− gain enthalpy gets less negative. Moving from the left side to the right side throughout a period, the electron gain enthalpy becomes more -ve. Halogens have a substantially negative electron gain enthalpy because they can receive one $\mathrm{e^{-}}$ to achieve the electrical configuration of noble gases. Noble gases have a positive electron gain enthalpy.

FAQs

1. Identify & explain the compounds with the lowest negative & the highest negative electron gain enthalpy (𝑺, 𝑷, 𝑭, 𝑪𝒍)?

The electron gain enthalpy grows more negative as we travel from the left side to the right side over a period. It also grows less negative as one moves down in a group. When an $\mathrm{e^{-}}$ is introduced to the 2p orbital, it repels more strongly than when it is added to the 3p orbital. As a result, phosphorus has the lowest -ve while chlorine has the highest -ve electron gain enthalpy.

2. Which element has the greatest electron gain enthalpy?

The maximum $\mathrm{e^{-}}$ gain enthalpy is found in chlorine.

3. Which element has the lowest electron gain enthalpy?

The lowest $\mathrm{e^{-}}$ gain enthalpy is found in mercury.

4. What is the distinction between electron affinity & electron gain enthalpy?

The major distinction between $\mathrm{e^{-}}$ gain enthalpy & $\mathrm{e^{-}}$ affinity is that the quantity of energy created when an isolated gaseous atom receives an electron is termed electron gain enthalpy. whereas electron affinity represents the atom's tendency to accept the electron.

5. Distinguish between electronegativity & electron gain enthalpy?

The main distinction between electronegativity & $\mathrm{e^{-}}$ gain enthalpy is that electronegativity is the tendency of an atom to attract $\mathrm{e^{-}}$ of a shared pair in a chemical compound to form a covalent bond, whereas $\mathrm{e^{-}}$ gain enthalpy is the quantity of energy released when an $\mathrm{e^{-}}$ is introduced to an isolated gaseous molecule. Furthermore, whereas electron gain enthalpy may be evaluated quantitatively, electronegativity cannot since it is qualitative.