Ionization In Thermodynamics

After size and ionisation energy, the third thing that helps make bonds is the energy change that happens when electrons are attached to a neutral atom. This energy is called the electron affinity, which is the amount of energy that is released when an electron is attached to an atom of the element. This energy is called the electron affinity. Most of the time, the electron affinity is positive, which means that when an electron attaches to an atom, energy does come out. When an electron comes in, it goes into a hole in the atom’s valence shell. Even though the electrons already there are repelled by it, it is close enough to the nucleus for there to be a net attraction between the two of them. Electrons have less power when they are inside an atom.

Electron affinity

In chemistry, the amount of energy released when an electron is added to a neutral atom to form a negatively charged ion is called electron affinity. Because measuring the electron affinities of atoms is challenging, values for just a few chemical elements, mostly the halogens, are known. These values were determined by measuring the temperatures of formation and lattice energies of elemental ionic compounds. The electron affinity of an element is a measure of its proclivity to operate as an oxidising agent (an electron acceptor) and is often connected to the chemical bonds formed by the element with other elements.

This is distinct from the enthalpy change associated with electron capture ionisation, which is classified as negative when energy is released. In other words, the difference between the enthalpy change and the electron affinity is negative.

X(g)  +  e−  →  X−(g) +  energy

Periodic trends

In a period, the affinity for electrons grows from left to right. Because of more nuclear attraction, the overall trend over a period changes.

Going down the group, the electron affinity should go down because the electron is getting farther away from the atom as it is added. It is less tightly bound, which means it is closer in energy to a free electron.

Electron affinity = 1 / atomic size

Atomic sizes get smaller over time because the nuclear force gets stronger. This means that electron gain enthalpy goes up as we move from left to right. When you move down a group in the periodic table, the atomic size gets bigger, which makes the value of electron gain enthalpy go down.

The first electron affinity of an element is always negative, or exothermic. The second electron affinity of the same element will always be positive, or endothermic, but not the same element. Because the second electron has to be forced into the mono negative ion, this is why this is the case. The Born-Haber cycle is used to figure out the electron affinity indirectly.

Electron gain enthalpy

Electron gain enthalpy is the energy that is created when a neutral gaseous atom gets an extra electron to make a gaseous negative ion, or anion, in the process. egH can be used to show it. The more energy that is released in the process above, the more electrons the element gains. A gaseous atom that loses an electron to become its equivalent anion is called “electron gain enthalpy.” This change in enthalpy is called “electron gain enthalpy.” The electron gain enthalpy method shows how much energy is used. It also tells how strong the extra electron that is added to the gaseous atom is. Electrons get more energy when there is a lot of energy released in the chemical reaction. Such reactions can be both exothermic and endothermic in nature, which means that they both release and take in energy based on the elements that make them up.

Factors affecting electron gain enthalpy

Atomic Size: As the atomic size of a molecule decreases, the distance between the nucleus and the final cell rises. As a result, the force of attraction between the core and the freshly introduced electron decreases and the force of attraction becomes less negative.

Nuclear Charge: As the total negative charge increases, the force of attraction between the newly acquired electron and the nucleus increases, resulting in a higher negative enthalpy in nature.

Electronic Configuration: In general, elements with accurate half-filled or completely filled orbitals are relatively stable. Energy must be supplied to such elements in order for them to undergo electron addition. As a result, the electron gain enthalpy of such elements is quite considerable.

Ionization enthalpy

It is called ionisation energy, or ionisation potential, in chemistry and physics, the amount of energy it takes to remove an electron from an atom or molecule that is alone. There is an ionisation energy for each electron that is removed. The ionisation energy associated with the removal of the first (most freely held) electron is the most commonly used.

In an electric discharge tube, a fast-moving electron from an electric current hits a gaseous atom of the element, causing it to lose one of its electrons. This is how the ionisation energy of a chemical element is measured. In general, joules are used by chemists, and electron volts are used by physicists. Hydrogen is made up of an electron that orbits around its nucleus, which is made up of one proton. To make it all the way out, it needs an ionisation energy that is 2.18 1018 joule (13.6 volts). The bigger the ionisation energy of an element, the more important it is that the nucleus has an electric charge, the size of the atom, and the way it has its electrons set up. The noble gases are the hardest to get rid of an electron from. The alkali metals are the easiest. The amount of energy needed to remove electrons from an atom keeps going up as the atom loses electrons. This is because the positive charge on the nucleus of the atom doesn’t change, so with each removal of an electron, the rest are held more tightly. If you want to make atoms or molecules ionise, you need to get enough energy (in joules) to make one mole of atoms or molecules ionise (i.e., the amount in grammes of a given substance numerically equal to its atomic or molecular weight). One mole of hydrogen atoms has an atomic weight of 1.00 grams, and each mole of hydrogen has an ionisation energy of 1,312 kilojoules.

Conclusion

In this article we looked at and got a detailed view of Ionization in thermodynamics in general along with electron affinity, electron gain enthalpy and ionization enthalpy. 

We Also read about the other various components and factors involved with all these terms.