Orbits are only said when the number of electron layers is specified, such as 1s 2p orbit.

The S sublayer is an orbit with angular quantum number L of 1, which can accommodate a pair of electrons with opposite choices.

The P sublayer is an orbit with angular quantum number of 2, which can accommodate three pairs of electrons with opposite self-selection.

The D sublayer is an orbit with angular quantum number of 3, which can accommodate five pairs of electrons with opposite selection.

Below are the F and G sublayers, etc., containing 2L+ 1 electrons.

In multi-electron atoms, we arrange electrons in different electron layers according to their own energy. The electron shell is represented by n, and the value range of n is a positive integer, that is, n= 1, 2, 3, 4, 5 ... The greater the value of n, the higher the energy of electrons.

However, the energies of electrons in the same electron layer are not exactly the same. In order to distinguish these electrons with different energies, we discharge them into different sublayers. The sublayers can be represented by S, P, D, F, G ... According to the arrangement of energy levels, the sublayers of each electron layer are equal to the ordinal number of the electron layer. For example:

N= 1, and there is only one S sublayer.

N=2, there are two sublayers, s and p.

N=3, there are three sublayers: s, p and d.

The rest can be inferred.

Each sublayer in the electron layer is called an energy level.

The shape of each sublayer is different, and the shape of each sublayer has different extension directions in space. The S, P, D and F sublayers have 1, 3, 5 and 7 extension directions respectively, and each extension direction is called a track. Generally speaking, the orbit of S sublayer can be called S orbit, the orbit of P sublayer can be called P orbit, and the orbit of D sublayer can be called D orbit. In order to describe the orbit accurately, it is necessary to combine the electron layer with the sublayer, such as 1s, 2s, 2p, 3s, 3p, 3d and so on.

Atoms have extra-nuclear electrons, which should be arranged in orbit;

Generally speaking, the exonuclear electron layer is divided into K, L, M, N, O, P,

However, scientists have found that on each layer, there are many regions with different energies, that is, electron sublayers;

There are four kinds of electron sublayers, which are represented by letters S, P, D and F respectively.

Electron sublayer, in fact, you can understand it as electron orbital group,

There are several tracks on each sublayer,

There are 1 orbits in the S sublayer, 3 orbits in the P sublayer, 5 orbits in the D sublayer and 7 orbits in the F sublayer.

These orbits can be used to load electrons, and each orbit can accommodate two electrons with opposite spin directions (that is, the two electrons rotate in different directions).

Then I'll find you some practical information, which will be very useful to you in the future:

(1) k layer only has s sublayer, referred to as1s; Abbreviation; L layer has two sublayers, S and P, which are referred to as 2s and 2p for short. M layer has three sublayers, S, P and D, which are referred to as 3s, 3p and 3D for short. Wait a minute.

(2) Because of the existence of sublayers, the energy of electrons in the same electron layer is different, even the energy of the high sublayer of the low electron layer is greater than that of the low sublayer of the high electron layer. The energy of each sublayer is arranged from low to high as follows:

1s，2s，2p，3s，3p，4s，3d，4p，5s，4d，5p，6s，4f，5d，6p，7s，5f ...................................................................................................

③: If you want to know more about the electron sublayers, you can learn about them: the lowest energy principle, Hont Hungary principle, Pauli incompatibility principle, and Hont Hungary special case, as follows: 1. The electron configuration principle outside the nucleus is in a stable state, and the electrons outside the nucleus will be arranged according to the lowest energy principle as much as possible. In addition, because electrons cannot all be crowded together, they must also abide by Pauli exclusion principle and Hunter rule. Generally speaking, among these three rules, 1. The principle of minimum energy When electrons are arranged outside the nucleus, the energy of electrons should be as low as possible. How can we minimize the energy of electrons? For example, if we stand on the ground, we won't feel any danger; If we stand on the roof of the 20th floor, we will feel scared when we look down. This is because the higher the potential energy of an object, the higher the potential energy of the object. Just like a free fall, we have never seen an object automatically rise from the ground into the air. If an object wants to go from the ground to the air, it must have an external force. The electron itself is a substance with the same properties, that is, it always wants to be in a safer (or stable) state (ground state), that is, the state with the lowest energy. When there is an external force, an electron can also absorb energy to a higher energy state (excited state), but it always wants to return to the ground state. Generally speaking, the closer to the nucleus, the lower the electron energy, and with the increase of the number of electron layers, the energy of the electron becomes larger and larger; In the same layer, the energy of each sublayer increases in the order of S, P, D and F. The total result of these two actions shows that the order of electrons outside the nucleus is: 1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p...2. Pauli incompatibility principle We already know that the motion state of an electron should be from four aspects. There are no and impossible two electrons in the same atom with exactly the same motion state, which is told by Pauli exclusion principle. According to this law, if two electrons are in the same orbit, then the spin directions of these two electrons must be opposite. In other words, each orbit can only hold two electrons with opposite spin directions. It's like taking an elevator. Everyone is equivalent to an electron, and every elevator is equivalent to a track. Assuming that the elevator is small enough, each elevator can only be used by two people at the same time. One person must sit with his head up and the other person stands upside down (in order to make full use of space). According to the Pauli exclusion principle, we know that the S sublayer has only 1 orbit, which can accommodate two electrons with opposite spins. The p sublayer has three orbits, and the total * * * can accommodate six electrons; The F sublayer has five orbitals, and the total * * * can hold 10 electrons. We also know that the first electron layer (K layer) has only 1s sublayers, which can accommodate at most two electrons. The second electron layer (L layer) includes two sublayers, 2s and 2p, which can hold 8 electrons in total. The third electron layer (M layer) includes 3s, 3p and 3d sublayers, and the total * * * can hold 18 electrons ... The total * * * of the nth layer can hold 2n2 electrons. 3. Hunt's hunting rule summarized from the experimental results of spectrum has two meanings: First, when electrons are arranged outside the nucleus, they will occupy different orbits as much as possible, and their spins are parallel; The second meaning of Hunter's Law is that for the same electron sublayer, when it is full (s2, p6, d 10, f 14), half full (s 1, p3, d5, f7) and completely empty (s0, p0, d0, f0). This is similar to the situation when we take the elevator. Either the elevator is empty, or there is only one person in the elevator, or there are two people crowded in the elevator. Everyone feels more equal and no one complains. If there are two people crowded in some elevators, and there is only one person in some elevators, or there is only one person in some elevators, and there is no one in some elevators, people will inevitably complain. This is the so-called unstable state. Second, the method of extranuclear electron configuration For the extranuclear electron configuration of an element atom, the number of extranuclear electrons (that is, the number of atoms, protons and nuclear charges) of the atom is first determined. For example, element 24 chromium has a total of 24 electrons outside the nucleus, and then these 24 electrons are arranged from the sublayer with the lowest energy of 1 to the sublayer with higher energy, only after the previous sublayer is filled. How to arrange the outermost electrons should also refer to Hunter's Law. For example, the 24 extranuclear electrons of element 24 chromium are arranged in sequence as 1s 222 p 63s 23 p 64s 23d 4. According to Hunt's law, the D sub-layer is relatively stable when it is half full, so its arrangement formula should finally be: 1s 22 p 62 p 63s 23 p 6438+03d 5. Three. The application of extranuclear electron configuration in middle school chemistry 1. The relationship between the extranuclear electron configuration of the atom and the orbital expression and the schematic diagram of the atomic structure: The arrangement of the extranuclear electrons of the atom is exactly the same as that described in the orbital expression. Relatively speaking, the orbital expression is more detailed, which can not only clearly indicate which electron layers and electron sublayers the extranuclear electron configuration of the atom is in, but also indicate whether these electrons are in the same or opposite spin state. In the schematic diagram of atomic structure, we can see that the electrons are arranged in layers outside the nucleus, but there is no indication on which sublayers the electrons are distributed or the spin of each electron. Its advantage is that it can directly see the nuclear charge number of atoms (or the total number of electrons outside the nucleus). 2. The relationship between the extranuclear electron configuration of an atom and the periodic law of elements lies in the atom, the nucleus is located in the center of the whole atom, and electrons move around the nucleus at high speed outside the nucleus. Because electrons move in different regions far away from the nucleus, we can think that electrons are arranged in layers outside the nucleus. According to the three principles of extranuclear electron configuration, the extranuclear electron configuration of all atoms is around the nucleus, and it is found that the extranuclear electron configuration obeys the following laws: the extranuclear electrons are distributed in the low-energy electron layer (closer to the nucleus) as much as possible; If the number of electron layers is n, the maximum number of electrons in this layer is 2n2. No matter which layer, if it is the outermost layer, the number of electrons in this layer cannot exceed 8, and if it is the penultimate layer (the second outer layer), the number of electrons in this layer cannot exceed 18. This result determines the periodic variation law of the extranuclear electronic configuration of elements, and classifies the elements in the same column in the periodic table into one group according to the same outermost electronic configuration. According to the periodic change of electron configuration outside the nucleus, the periods are divided, for example, the number of elements in the first period is 2, the number of elements in the second period is 8, which is determined by 1s 1~2, and the number of elements in the third period is 8, which is determined by 2s 1~22p0~6. It can be seen that the law of the extranuclear electronic configuration of elements is the main basis for the division of the periodic table of elements and the root of the periodic changes of element properties. For the same group of elements, from top to bottom, with the increase of the number of electron layers, the atomic radius becomes larger and larger, the attraction of the nucleus to the outermost electrons becomes smaller and smaller, and the outermost electrons are more and more easily lost, that is, the metallicity becomes stronger and stronger; For elements with the same period, with the increase of nuclear charge, the attraction of nucleus to outer electrons becomes stronger and stronger, which makes the atomic radius gradually decrease, the metallicity becomes worse and worse, and the nonmetal becomes stronger and stronger. 3. The extranuclear electron configuration and chemical properties of elements are directly determined by the extranuclear electron configuration of elements. For example, the electronic structure of the outermost layer of alkali metal elements can be expressed as ns 1, indicating that alkali metal elements are generally easy to lose the outermost layer of 1 electrons (valence electrons) and become positive monovalent cations, thus forming a stable structure of inert gas (this property is strong reduction); The electronic structure of the outermost layer of halogen can be expressed as ns2np5, which shows that halogen can easily get 1 electron and become negative 1 anion, thus forming a stable structure of inert gas (this property is strong oxidation). Of course, they can also lose the outermost valence electrons, showing the equivalent states of+1, +3, +5 and +7. For the same group of elements, with the increase of the number of electron layers, the metallicity becomes stronger and stronger, and the nonmetal becomes weaker and weaker, which also depends on the extranuclear electronic configuration of the element atoms. Under the guidance of these theoretical knowledge (as shown in the following formula), we can understand and infer the chemical properties of elements and their changing rules, thus greatly reducing our memory.