Why do atoms undergo hybridization and excitation?

I teach inorganic chemistry. Some students also asked.

I guess there's a question of order that gets me wrong. Taking methane as an example, it should be the tetrahedral structure that we discovered first, and the original covalent bond theory cannot be reasonably explained, and the hybrid orbital theory is supplemented later. Instead of methane actively dehybridization, we later discovered the tetrahedral structure.

Methane does not have this agency.

Also, if we have to explain it, we can explain it from the point of view of energy. You can calculate that after deducting the amount of energy it takes to excite an electron, the amount of energy released to form four bonds is larger; Or only two bonds release a lot of energy.

In chemistry, structure and energy should be two important main threads, and we can consider many issues from these two perspectives.

Finally, if you are a chemistry student, I strongly urge you to abandon the spirit of asking why you see any phenomenon. It's so tiring. We study chemistry at the atomic and molecular level, not at the atomic and molecular levels.

Methane, for example, was already a hybrid structure before the dinosaurs. Another question is that this is just a theory, whether it is the best and most reasonable, I personally think it is not necessarily. As we gradually understand the microscopic world, this theory may be further refined or even completely overturned.

We can't be tied down by it.

In order for there is only one electron in the orbital, chemical bonds can be formed with other elements.

If CH4 SP3 is hybridized, 4 bonds can be formed.

The way in which hybrid orbitals are judged is as follows:

1. Determine the number of lone electron pairs in the nanovolt-centric atom.

2.Find out the number of atoms attached to the central atom (i.e., the number of bonds formed).

3. If the sum of the two is equal to 2, then the central atom adopts sp hybridization; If it is equal to 3, then the central atom is hybridized with sp2; If it is equal to 4, then the central atom is hybridized with sp3.

In the process of bonding, due to the interaction between atoms, several different types of atomic orbitals (i.e., wave functions) with similar energy in the same atom can be linearly combined to redistribute energy and determine the spatial direction to form a new atomic orbital with an equal number of atoms.

Hybrid orbitals. In the process of bonding, several different types of atomic orbitals (i.e., wave functions) with similar energies in the same molecule due to the interaction between atoms.

Linear combinations can be carried out to redistribute energy and determine the spatial orientation to form an equal number of new atomic orbital cavities, which is called hybridization, and the new orbitals formed after hybridization are called hybrid orbitals.

The angular function of the hybrid orbital in a certain direction is much larger than that before hybridization, which is more conducive to the maximum overlap between atomic orbitals, so the hybrid orbital has a stronger bonding ability than the original orbital (the orbital is bonded after hybridization).

The hybrid orbitals try to take the maximum angle distribution in space, so that the repulsion energy between them is minimized, so the bond formed is relatively stable. The angles between different types of hybrid orbitals are different, and the molecules formed by the swimming Zheng after bonding have different spatial configurations.

Judging by the formula:

k = m+n (m is the number of lone electron pairs of the central atom, n is the number of groups bonded to the central atom).

m=(e-σdi)/2

e: The number of valence electrons in the central atom (the number of valence electrons is the number of outermost electrons) bond chain.

di: The maximum number of electrons that can be received by a group bonded to the central atom (di-electrons need to be received to reach a steady state).

k=2, there are two orbitals involved in hybridization, sp hybridization;

k=3, there are three orbitals involved in hybridization, sp2 hybridization;

k=4, there are four orbitals involved in hybridization, sp3 dsp2 hybridization;

k=5, there are five orbitals involved in hybridization, sp3d d4s hybridization;

k=6, there are six orbitals involved in hybridization, sp3d2 d2sp3 hybridization;

Take H2S as an example, the central atom of H2S is sulfur, e=6;Hydrogen linked to sulfur needs to receive 1 electron to reach steady state.

Thus, k=m+n=[6-(1+1)] 2+2=4 of H2S H2S is sp3 hybridized.

"I think this question can be explained from two aspects: the possibility and necessity of orbital hybridization: (1) Why is it possible for atomic orbitals to be hybridized? Because electrons have a wave nature, different waves have the property of superimposing each other to form new waves under certain conditions.

Therefore, in the process of compounding, different atomic orbitals of the same atom (i.e., different wave functions) may be further linearly combined to form new atomic orbitals, that is, the so-called hybrid orbitals. (2) Why do atomic orbitals need to be hybridized? It is uncommon for an atom to have an electron motion outside the nucleus (i.e., the electron configuration) in the ground state, and only an isolated atom is the most stable.

If the atom is in a conglomerate state, the conjugated electron configuration of this ground state is not the most stable. Matter has a tendency to reduce its own energy, so when atoms bond with each other, the outer orbits of the atoms must change in order to make the formed chemical bonds more stable and release more energy. In order to release more energy when atoms form bonds, there are generally two ways to change the electron configuration:

From the ground state to the excited state. The more single electrons in the excited state than in the ground state, more chemical bonds can be formed, and although the energy required to excite the electrons is required, the total energy of the system is lower. Orbital hybridization. After orbital hybridization, the energy of the system can be reduced.

Because one of the distinctive characteristics of the hybrid orbital is that it has a strong directionality, the shape of the orbital is very different from the original orbital, and it becomes one large and the other small. For example, if a carbon atom is bonded with other atoms with a sp hybrid orbital (the larger end), the overlap is much larger than that of a pure s or p orbital, so the bonding capacity is increased. In a nutshell, "atomic orbitals have the nature of waves, and several different atomic orbitals of the same atom can be formed into hybrid orbitals by linear combination."

The hybrid orbitals have a strong directionality, which enhances the bonding ability. However, isolated atoms do not hybridize on their own, as hybridization tends to lead to an increase in the energy of isolated atoms. ”

Hehe! Impulsive friend, your questions are profound and important! It's a problem that students who have just entered the university chemistry major are eager to solve!

1. First of all, as the teacher upstairs said, not every atom in a molecule has to be hybridized! So, what about the central atom (and the other can be called the coordination atom) in many molecules to be hybridized? Because the different atomic orbitals in the central atom (e.g. sp, sp2, sp3, sp3d, sp3d2 hybridization, etc.) hybridization can result in additional stabilization energy and the resulting compound is more stable (energy minimum principle)!

2. Not the atomic orbitals of every element can be hybridized (such as h and most of the main group metal element atoms)! Why? There are no superfluous (or semi-filled) atomic orbitals of different kinds!

3. Therefore, the atoms to be hybridized are, in general:

1), There are different kinds of atomic orbitals with fairly close energies and contain lone electrons (so many textbooks talk about hybradation) such as c

The energy of the 2s and 2p orbits is quite close to that of "Bar.

2) Another important reason is the perfect integer ratio or perfect molecular symmetry! Such as sp3 tetrahedral hybrid organic compounds --- hydrocarbons!

3) Hybridization in the OH field of the secondary group metal complexes such as [Fe(H2O)6]3+, the center of gravity Fe3+, the perfect SP3D2 regular octahedron!

Well, chemistry is simple, as long as you are willing to climb!

Good luck!

Not every atom will be hybridized.

For example, in a CO2 molecule, the C atom Sp is hybridized, while the O atom is not.

Hybridization: a theoretical explanation of the process in which atoms form molecules.

Hybridization is simply the recombination of atomic orbitals. When you examine o, the oxygen atom is the central atom; When you look at h, the hydrogen atom is the central atom; When you look at s, the sulfur atom is the central atom.

According to the hybrid orbital theory, s and o are both atoms bonded by hybrid orbitals.

In the five crystalline waters: the oxygen atoms are all sp3 hybridized, 4 electrons in 3 p orbitals and 2 electrons in s orbitals form 4 sp3 orbitals (1, 1, 2, 2), in which the two sp3 orbitals containing unpaired electrons and the unpaired electrons in the s orbital of hydrogen atoms form o-h covalent bonds.

In sulfate: sulfur atom is also sp3 hybridized, 4 electrons in 3 p orbitals and 2 electrons in s orbitals form 4 sp3 orbitals (1, 1, 2, 2), in which two sp3 orbitals containing unpaired electrons and unpaired electrons in p orbitals of two oxygen atoms form s o covalent bonds, and the other two sp3 orbitals containing paired electrons and empty p orbitals of the other two oxygen atoms form s o coordination bonds respectively (the oxygen atom is before bonding, the electronic distribution of p orbitals is composed of 2, 1,1 becomes 2,2,0).

o covalent bond o: non-hybrid. The electron distribution of the p orbital is 2,1,1, one of the p orbitals containing unpaired electrons forms a S o covalent bond with one of the sp3 orbitals containing unpaired electrons of one S, and the other p orbital containing unpaired electrons accepts electrons from Cu.

o of the coordination bond: no hybridization. Before the oxygen atom forms bonds, the electron distribution of the p orbital changes from 2,1,1 to 2,2,0, thus having an empty orbital. A sp3 orbital containing paired electrons of sulfur forms a so coordination bond with an empty p orbital.

In this way, the problem of 8-electron structure is solved, and the orientation of each chemical bond can be explained to a certain extent.

If you don't understand, please send an email to us.

According to the hybrid orbital theory, hybridization occurs when any atom forms a molecule, whether it is a central atom or not.

In general, however, how non-central atoms hybridize has little effect on molecular structure, so it is rarely discussed.

In copper sulfate pentahydrate, the O in the 5 H2O is all sp3 hybridized. The o in SO4 2- seems to be controversial and is SP or SP2 hybridization.

Simply put, the number of bonds (i.e., the number of connected atoms) of that atom plus the number of lone electron pairs [the number of lone electron pairs is equal to 1 2 (the number of valence electrons of that atom minus the number of atoms bound to the central atom multiplied by the maximum number of electrons that the atom bound to this atom can accept), the maximum number of electrons that an atom can accept, 1 for hydrogen, 8 for other atoms minus the number of valence electrons], and the sum of these two is 4, then sp3 hybridization, 3 is sp2 hybridization, and 2 is sp hybridization.

For example, NH3, where the hybrid mode of nitrogen atom is calculated as follows: nitrogen atom with 3 hydrogen atoms, the number of bonds is 3, the number of lone electron pairs is 1 2(5-3 1)=1, and the sum of bond and lone electron pairs is 4, so it is sp3 hybridization.

Well, since you ask this question, it means that you are at least studying chemistry.

This belongs to the content of inorganic chemistry, the theory of hybrid orbitals, which should be discussed in more detail in the book. Such a professional question cannot be explained clearly in three or two sentences.

δ number of lone pairs 1 is the sp number.