The ionization energy of an atom

The energy of ionization is the main characteristic of an atom. It determines the nature and strength of the chemical bonds that can form an atom. The reducing properties of a substance (simple) also depend on this characteristic.

The term "ionization energy" is sometimes replaced by the term "first ionization potential" (I1), meaning by this the smallest energy that is needed for an electron to escape from a free atom when it is in a state of energy that is called inferior.

In particular, for a hydrogen atom, so is the energy that is required to detach an electron from a proton. For atoms with several electrons there is the concept of the second, third, etc. Ionization potentials.

The ionization energy of a hydrogen atom is a sum, one component of which is the energy of an electron, and the other is the potential energy of the system.

In chemistry, the energy of the hydrogen atom is denoted by the symbol "Ea", and the sum of the potential energy of the system and the electron energy can be expressed by the formula: Ea = E + T = -Ze / 2.R.

This expression shows that the stability of the system is directly related to the charge of the nucleus and the distance between it and the electron. The smaller this distance, the stronger the charge of the nucleus, the more attracted they are, the more stable and stable the system, the more energy must be spent to break this connection.

It is obvious that the stability of systems can be compared in terms of the level of energy spent to destroy the bond: the more energy, the more stable the system.

The ionization energy of the atom - (the force that is necessary for the destruction of bonds in a hydrogen atom) was calculated experimentally. Today its value is known exactly: 13.6 eV (electron volts). Later, scientists, also with the help of a series of experiments, were able to calculate the energy required for the destruction of the atom-electron bond in systems consisting of a single electron and a nucleus with a charge twice that of a hydrogen atom. It was established experimentally that in this case 54.4 eV are required.

The known laws of electrostatics say that the ionization energy necessary to break the connection between opposing charges (Z and e), provided that they are located at a distance R, is fixed (determined) by the following equation: T = Ze / R.

Such an energy is proportional to the magnitude of the charges and, accordingly, is inversely related to the distance. This is quite natural: the stronger the charges, the stronger the forces connecting them, the more powerful the effort is required to break down the bond between them. The same applies to distance: the smaller it is, the stronger the ionization energy, the more forks will have to be applied to break the connection.

This reasoning explains why the system of atoms with a strong nuclear charge is more stable and needs more energy to detach the electron.

The question immediately arises: "If the nuclear charge is only twice as strong, why is the ionization energy necessary for electron detachment not increased by two, but by a factor of four?" Why is it equal to the doubled charge taken in square (54,4 / 13,6 = 4 )? ".

This contradiction is explained quite simply. If the charges Z and e in the system are relatively in a mutual state of immobility, then the energy (T) is proportional to the charge Z, and they increase proportionally.

But in a system where the electron with charge e makes the core revolutions with charge Z, and Z amplifies, the radius of rotation R decreases proportionally: the electron is attracted to the nucleus with greater force.

The conclusion is obvious. The ionization energy is acted upon by the charge of the nucleus, the distance (in radius) from the nucleus to the highest point of the charge density of the external electron; The repulsive force between the outer electrons and the measure of the penetrating ability of the electron.