How the electrons in the atom are distributed outside the nucleus is a question of interest to both the physics and chemistry circles. With the development of aufbau principle and incompatibility principle, shell theory has gradually become a major theory. Electrons move in a series of shells, and electrons are gradually filled from low-energy orbitals to high-energy orbitals.
There are many challenges to the shell structure theory and the Madelong rule, which are not consistent with many experimental phenomena.In 1969, on the 100th anniversary of the periodic table, chemist Per-Olov Löwdin declared this derivation to be one of chemistry’s major theoretical challenges1.Even 150 years on, theoretical chemists, physicists and philosophers still need to step in to comprehend the gestalt of the periodic table and its underlying physical explanation2.
Because the multi-electron distribution in the atom involves many-body problems, the accurate solution can’t be obtained by solving the equation. From the point of view of spatial geometry, we construct the nuclear structure model based on the principle of dynamic symmetric equilibrium. Through the correspondence between electrons and protons, we obtain the dynamically symmetrical and cascading electron distribution. This electronic configuration corresponds very well to the periodicity of the elements and the properties of each element.
In this model, the electrons of each element are divided into three parts, both sides and the middle. The number of electrons and orbitals on both sides are the same and the electrons are symmetrically distributed. The parity of the ordinal number of elements is mainly reflected in the middle, and there is a single electron orbit in the middle of the element with odd ordinal number. As shown in Fig. 1、2, the electron distribution of the first 20 elements.
In Fig. 1、2, orbitals are divided into two categories, which are divided according to the number of electrons in the orbitals. The number of electrons in the orbit is even, which belongs to the stable orbit, in which the electrons belong to the stable electrons. In the picture, it is represented by a black loop and a ball, respectively. When there are only one or three electrons in the orbit, they belong to the valence electron orbit, and the electrons in the orbit are valence electrons, which are represented by red rings and balls, respectively.
The electron orbitals of elements 1–4 are on an axis. Starting from element 5, it distributes into three-dimensional space, and five electrons of element B form five valence electron orbitals. With the increase of the number of electrons, the new electrons gradually enter the original orbitals or merge orbitals, and the number of valence electron orbitals decreases gradually. Elements 6 to 10 have 4, 3, 2, 1 and 0 valence electron orbitals, respectively. Starting from element 7 N, the electron orbitals on both sides of element 7 and 8 are fused together. There are three electrons in the orbitals on both sides of element 7 and 8, and there are four same orbitals in elements 9, 10, 11, 12, 13 and 15. Elements 17, 18, 19 and 20 all have four electron pairs in the same layer. It can be seen that the number of electrons in the orbit tends to reach an even number.
Valence electron orbitals can merge, in which electrons can be transferred or deviated. Electrons transfer or shift from the position of high potential energy to the position of low potential energy, and the orbitals with basically the same potential energy merge into a new orbit. In this way, we can analyze the gain and loss of electrons in each element from the number and state of valence electron orbitals, and explain the reasons for the existence of common valence of each element. For example, the O atom has three orbitals, and the middle is a stable orbital, which does not need to add or subtract electrons. The orbitals on both sides need to get an electron from other atoms in order to stabilize the state. Therefore, this electron distribution of O corresponds to the usual valence-2 of O.
The atoms of alkali metal elements and alkaline earth metal elements are all valence electron orbitals with high potential energy, in which the electrons are easy to be lost, so their valence is usually + 1 and + 2, respectively.
Halogen elements have only one valence electron orbital with low potential energy in the atom, so it is easy to obtain one electron, and their valence is usually-1. The valence electron orbital potential energy of these elements is consistent, so the corresponding valence is relatively simple. They often make the number of electrons in the orbit even by means of electron transfer.
The potential energy of the four valence electron orbitals of C and Si atoms is the same, and the potential energy state is in the middle, in which the electrons are neither easy to lose nor easy to get other electrons. Generally, when combined with other valence electron orbitals, the number of electrons reaches an even number and forms new orbitals, and the probability of electrons appearing in the position of relatively low potential energy is relatively high. Therefore, their valence is usually-4 and + 4.
There are valence electron orbitals with different potential energies in the atoms of elements B, N, Al, P and S, and there are many ways to gain and lose electrons. Therefore, they have multiple common valences.
The number of valence electron orbitals of B and Al is 5, and there is one low potential energy valence electron orbital in the middle, which can absorb one electron from four adjacent high potential energy valence electron orbitals. Therefore, B and Al usually show the state of three high potential energy valence electron orbitals, and their valence is usually + 3. The state of more valence electron orbitals can also be shown in certain cases, for example, after one electron of Na atom is obtained in the middle of B and Al in NaBH4, NaAl (OH) 4, the four valence electron orbitals bind to four H and OH respectively.
P has seven valence electron orbitals, one low potential energy valence electron orbit in the middle, four symmetrically distributed high potential energy valence electron orbitals, and two valence electron orbitals with lower potential energy at both ends. The number and state of the orbitals in the middle are similar to those of Al, in which the low potential energy orbitals obtain one electron from four high potential energy orbitals, showing the state of five valence electron orbitals. For example, in the PF5 molecule, three valence electrons in the middle and two electrons at both ends are transferred to five fluorine atoms to form a triangular bipyramidal structure, and the valence of P is + 5. When the electrons with higher potential energy enter the low potential energy orbitals in the middle, the four symmetrically distributed high potential electrons can also be in equilibrium. For example, in the PH3 molecule, the valence electron orbitals in the middle and at both ends get electrons from the H atom to form stable orbitals, and the P atom gets three electrons with a valence of-3. It can be seen that the level of orbital potential energy is a relative concept.
There are two valence electron orbitals in the N atom. There are three electrons in each of the valence electron orbitals on both sides. There is only one electron in the valence electron orbit in the middle. The two sides combine electrons in the way of 3 + 1, and the middle combine electrons in the way of 1 + 1, so that the number of electrons in the orbit reaches an even number. They not only have different potential energy states, but also have different binding modes with other valence electron orbitals. Therefore, N shows a variety of states of gain and loss of electrons and has multiple valence. Electrons can be obtained from three valence electron orbitals, for example, the valence of NH3, N is-3. Each of the three valence electron orbitals can lose one electron, for example, the valence of NF3, N is + 3. Although there are three electrons on each side of the orbitals of N and O, the states of the orbitals are quite different. The three electrons in N orbitals have partial single electron properties and their potential energy is higher than that of O. For example, in HNO3 molecules, the electrons in the valence electron orbitals on both sides of N move to O atoms; the valence electron orbitals in the middle of N absorb one electron of H atom, where the valence of N is + 5.
The motion space of the three single electrons on each side of the S atom is not in the same space layer, and only a small part of the motion region of the top one single electron is connected to the adjacent two single electrons. Therefore, it is often shown as 6 valence electron orbitals, and + 6 valence is the common valence of S. The potential energy of the valence electron orbitals at the top is lower than that of the valence electron orbitals on both sides, and it is easy to obtain electrons, and S can also have-2 valence. For example, in H2S molecules, the orbitals at each end of S absorb an electron from an H atom.
The state of the valence electron orbitals in the atom determines the expression of the valence of the elements. When the orbital states are consistent, the common valence of the elements is usually relatively simple. The atoms of elements have valence electron orbitals with different potential energy and different orbital binding modes, so there are many ways to combine with other atoms, and the valence of elements will be more.
The gain and loss of interatomic electrons can be obtained from the number, potential energy and binding mode of valence electron orbitals, which has a natural corresponding relationship with the main valence of elements.
This electronic configuration has the following characteristics: 1. The symmetrical cascading distribution of electrons, and the electrons in the same layer tend to form a symmetrical distribution of four electrons or four pairs of electrons. 2. Electrons tend to move in low potential energy orbitals. 3. The number of electrons in the orbit tends to reach an even number, which is the basic rule for increasing and decreasing electrons in the orbit. It is applicable both within and between atoms and has consistency.