Electron Gain Enthalpy - Meaning, Definition, Differences, Factors, FAQs

What is Electron Gain Enthalpy?

The energy produced when a neutral isolated gaseous atom receives an extra electron to form the gaseous negative ion, or anion, is called electron gain enthalpy. ΔegH can be used to represent it. The bigger the quantity of energy released in the above process, the higher the element's electron gain enthalpy. The enthalpy change associated with an isolated gaseous atom (X) when it gains an electron to form its equivalent anion is known as electron gain enthalpy (ΔegH). The reaction is as follows:

X (g) + e- → X (g)

The strength with which an additional electron is attached to an element is measured by its electron gain enthalpy. It is measured in kJ per mole or electron volts per atom. When an electron is added to an atom, the process can be either endothermic or exothermic.

When an electron is added to an atom, energy is released. As a result, the electron gain enthalpy is negative.

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Chlorine is the element with the highest electron gain enthalpy. Its ΔegH value is – 349 KJ/mol

Noble gases have positive electron gain enthalpies. They have fully filled shells and energy is required to add an electron.

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What is electron affinity?

The term "electron affinity" refers to a love for electrons. It is equal to the negative of the electron gain enthalpy. We can find out a relationship between electron gain enthalpy and electron affinity using thermodynamic concepts.

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Electron gain enthalpy = Electron affinity – 5/2RT

R is the universal gas constant.

T is the Kelvin scale of temperature.

H

-73




He

+48

Li

-60

N

0.0

O

-141

F

-328

Ne

+116

Na

-53

P

-74

S

-200

Cl

-349

Ar

+96

K

-48

As

-77

Se

-195

Br

-325

Kr

+96

Rb

-47

Sb

-101

Te

-190

I

-295

Xe

+77

Cs

-46

Bi

-101

Po

-174

At

-270

Rn

+68

Related Topics link

  • Electronic Configuration of First 30 Elements
  • Homologous Series
  • Atomic radius in periodic table in basic chemistry
  • Classification of Elements in Modern Periodic Table

Difference Between Electron Gain Enthalpy and Electron Affinity

ELECTRON GAIN ENTHALPY

ELECTRON AFFINITY

  • It is the energy released to the surrounding when an electron is gained

  • It is the energy absorbed by the surrounding when and electron is gained

  • Electron gain enthalpy has a negative value

  • Electron affinity has a positive value

Factors Affecting Electron Gain Enthalpy

Atomic Size

The distance between the nucleus and the last shell that receives incoming electrons increases as the size of the atom increases. The force of attraction between the nucleus and the incoming electron is reduced. As a result, the electron gain enthalpy decreases.

  1. Nuclear Charge

The force of attraction between the nucleus and the incoming electron increases as the nuclear charge increases. As a result, the enthalpy becomes more and more negative.

  1. Electronic Configuration

Elements with orbitals that are exactly half full or totally filled are extremely stable. To add an electron, you must provide energy. As a result, their electron gain enthalpy is positive. Going from top to bottom in a group, the electron gain enthalpy gets less negative. Going from left to right in a period makes it more negative.

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Variation of Electron Gain Enthalpy

(Variation of ΔegH)

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Within a Group

  • As we move down the groups, the electron gain enthalpy gets less negative.

  • The atomic size and nuclear charge grow as we progress down a group. However, the effect of increasing atomic size is far more pronounced than the effect of increasing nuclear charge.

  • The nucleus's attraction to the incoming electron lessens as the atomic size increases. As a result, the electron gain enthalpy decreases.

  • The highest negative electron gain enthalpy is found in chlorine.

  1. Along a Period

  • In a period from left to right, the electron gain enthalpy increases. It becomes more and more negative.

  • The atomic size shrinks and the nuclear charge increases as we walk over a period from left to right. Both of these factors increase the nucleus's attraction to the incoming electron. As a result, as you move from left to right, the electron gain enthalpy gets increasingly negative.

  • The highest negative electron gain enthalpy is seen in halogens. As we progress from chlorine to iodine, the electron gain enthalpies grow less and less negative as their atomic radii increase.

  • The force with which the additional electron is attracted by the nucleus decreases as the distance between the nucleus and the subshell that receives it rises, and therefore the electron gain enthalpy becomes less negative as we proceed down the group from Cl > Br > I.

Related Topics link

  • Periodic Table Elements
  • 118 elements, their symbols and their atomic numbers
  • Rutherfords Model of Atoms and Its Limitations
  • Reactivity series
  • First 20 Elements

Exceptions in Electron Gain Enthalpy

  • In the case of Chlorine and Fluorine, the negative electron gain enthalpy value of Chlorine is greater.

Element

Electron gain enthalpy (KJ/mol)

Fluorine

-328

Chlorine

-349

Bromine

-325

Iodine

-295

Astatine

-270.1

  • Sulphur has a higher negative value than oxygen when compared to the trends followed in other periods.

Oxygen is much smaller when compared to Sulphur. As oxygen has a high electron density, adding an electron is difficult. Sulphur, on the other hand, is comparatively bigger and has a higher negative electron gain enthalpy than oxygen.

Electron gain enthalpy of chlorine is more than that of fluorine

Because of its small size, Fluorine's Electron Gain Enthalpy is less negative than that of Chlorine. The electron-electron repulsion in the relatively compact to 2p subshell is comparatively high due to its small size. As a result, the incoming electron is not accepted with the same ease as chlorine.

Noble Gases have a positive electron gain enthalpy.

The atoms of noble gases have entirely filled their subshells. As a result, their valence orbitals are full, and the extra electron must be deposited in an orbital in the next higher shell. As a result, energy must be provided in order to add on more electrons and hence the electron gain enthalpy is positive.

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