# Electron affinity and ionization energy relationship to power

### Ionization Energy and Electron Affinity

Oxygen - Electron Affinity - Electronegativity - Ionization Energy of Oxygen. This article summarizes key chemical and thermal properties of this. As far as I know the terms ionization energy and electron affinity are related to isolated atoms (or assemblies of isolated atoms = 1 mol), while work function is. Iron - Electron Affinity - Electronegativity - Ionization Energy of Iron. This article summarizes key chemical and thermal properties of this.

Click here to see a solution to Practice Problem 3 The magnitude of the first ionization energy of hydrogen can be brought into perspective by comparing it with the energy given off in a chemical reaction.

## What are differences among work function, ionisation energy and electron affinity?

When we burn natural gas, about kJ of energy is released per mole of methane consumed. The first ionization energy for helium is slightly less than twice the ionization energy for hydrogen because each electron in helium feels the attractive force of two protons, instead of one.

Because the electron in a 2s orbital is already at a higher energy than the electrons in a 1s orbital, it takes less energy to remove this electron from the atom.

The first ionization energies for the main group elements are given in the two figures below. Two trends are apparent from these data. In general, the first ionization energy increases as we go from left to right across a row of the periodic table.

The first ionization energy decreases as we go down a column of the periodic table. The first trend isn't surprising.

We might expect the first ionization energy to become larger as we go across a row of the periodic table because the force of attraction between the nucleus and an electron becomes larger as the number of protons in the nucleus of the atom becomes larger. The second trend results from the fact that the principal quantum number of the orbital holding the outermost electron becomes larger as we go down a column of the periodic table.

Although the number of protons in the nucleus also becomes larger, the electrons in smaller shells and subshells tend to screen the outermost electron from some of the force of attraction of the nucleus. Furthermore, the electron being removed when the first ionization energy is measured spends less of its time near the nucleus of the atom, and it therefore takes less energy to remove this electron from the atom.

For ionization of a diatomic molecule the only nuclear coordinate is the bond length. The lower curve is the potential energy curve of the neutral molecule, and the upper curve is for the positive ion with a longer bond length.

Ionization of molecules often leads to changes in molecular geometryand two types of first ionization energy are defined — adiabatic and vertical. The specific equilibrium geometry of each species does not affect this value. Vertical ionization energy[ edit ] Due to the possible changes in molecular geometry that may result from ionization, additional transitions may exist between the vibrational ground state of the neutral species and vibrational excited states of the positive ion.

In other words, ionization is accompanied by vibrational excitation. The intensity of such transitions are explained by the Franck—Condon principlewhich predicts that the most probable and intense transition corresponds to the vibrational excited state of the positive ion that has the same geometry as the neutral molecule.

This transition is referred to as the "vertical" ionization energy since it is represented by a completely vertical line on a potential energy diagram see Figure. For a diatomic molecule, the geometry is defined by the length of a single bond. The removal of an electron from a bonding molecular orbital weakens the bond and increases the bond length.

## How are electron affinity and ionization energy related?

In Figure 1, the lower potential energy curve is for the neutral molecule and the upper surface is for the positive ion. Both curves plot the potential energy as a function of bond length.

The horizontal lines correspond to vibrational levels with their associated vibrational wave functions. Since the ion has a weaker bond, it will have a longer bond length.

### What are differences among work function, ionisation energy and electron affinity?

This effect is represented by shifting the minimum of the potential energy curve to the right of the neutral species. The adiabatic ionization is the diagonal transition to the vibrational ground state of the ion.

Vertical ionization involves vibrational excitation of the ionic state and therefore requires greater energy.