Model of atom to molecule
The previous publication received a negative assessment with the wording “why should we place such elementary things here”. Therefore, I immediately warn you that this material is intended, first of all, for schoolchildren starting to study chemistry. And also for those to whom this subject was incomprehensible during the school years. I would put an article on a popular specialized resource for schoolchildren, if it existed.
And yes, I'm aware of the existence of a model of an atom in which an electron is a probability wave located near the nucleus. But as a rule, it is difficult for a student to imagine how probability can combine atoms into molecules. Therefore, set out "on the fingers."
Connection of atoms into molecules
')
Our world does not exist in the form of individual atoms, they are somehow connected to each other. What exactly?
Take two hydrogen atoms. Each of them contains one proton and one electron, so the total charge of each of these atoms is zero.
Coulomb's law
F = k * q1 * q2 / r ^ 2
tells us that neutral bodies should not be attracted to each other
(q1 = 0, q2 = 0) .
This means that hydrogen (and any other chemical element) should exist only in the form of atoms, and never merge into molecules. In fact, hydrogen atoms are always connected in pairs. Why?
Let's take two pieces of metal, and arrange them in parallel at a short distance from each other.
Both segments contain the same number of protons and electrons, therefore, the total charge of each of them is zero. So, they have no reason for mutual attraction.
We know that in metals part of the external electrons leave their atoms and freely walk between the ions (left atoms) of the metal crystal lattice. And these electrons are distributed, on average, evenly.
Imagine that we somehow managed to move part of these free electrons to the left side of the lower metal segment. In this case, in its right side there will be a shortage of electrons.
We got the so-called dipole: the left side of the segment is negatively charged, the right side is positive. Fine. And what will happen in the upper segment? We know that like charges repel each other, and opposite ones attract each other. Consequently, the electrons of the upper segment, starting from the electric fields of the electrons of the lower segment, will go to the right side. That is, the picture of the distribution of electrons in these two segments of metals will become a mirror image:
This effect of charged objects on neighboring objects, leading to a redistribution of charges in them, is called electrostatic induction.
Now the most interesting thing: the positively charged nuclei of atoms in the left part of the upper segment are opposite to the electrons collected in the left part of the lower segment. And opposite charges attract. So, the left parts of the segments will begin to attract each other!
The same thing will happen on the right side of the segments - only mirror. And the right ends of the segments will also be attracted to each other. Wonderful, isn't it? The redistribution of charges inside one of the segments of conductors led to the mutual attraction of these two segments!
And what happens if you now move the free electrons of the lower segment to its right end? Then the free electrons of the upper segment will move to the left end. That is, by moving electrons back and forth in one of the segments, we force the electrons of a neighboring segment that is not related to the first to move! Such an effect of the movement of electrons in a single conductor on the movement of electrons in an adjacent conductor is called electrodynamic induction.
Although this does not apply to our topic, we note that we have studied in a somewhat simplified manner how the antenna and receiver work during radio transmission.
We can arrange these two pieces of metal differently - with the ends to each other:
If we are able to move the electrons, for example, to the right side of the left segment, the electrons of the right segment, starting from them, will also move to the right side of the right segment:
And in this case, these two pieces of metal will begin to attract each other, since their near ends have an opposite charge. Special attention should be paid to the fact that in the second variant of the arrangement of the segments, the force of their mutual attraction will be weaker, since only their opposite ends are attracted, while in the first variant of the arrangement of the segments, both the left and the right are attracted to each other. the ends.
But how does this relate to the union of atoms? Let's look at a hydrogen atom. It has an electron moving around the nucleus. And if there is a second hydrogen atom nearby, this electron will force the neighbor's electron to move in much the same way as they moved in our metal segments - while the electron of one of the atoms is on one side of its atomic nucleus, the next one will be forced to be on the opposite side of its atom.
Here, of course, the influence is not one-sided, but mutual - as the first electron affects the second, and the second affects the first. But the most important thing is that these two atoms will be attracted in the same way as two pieces of metal were attracted in the second variant of their mutual placement (with their ends to each other).
The essence is the same: the electrons are kept away from each other, allowing opposite charges to attract each other. Imagine that the electron of one of the atoms appeared between the nuclei of two neighboring atoms, while the electron of the neighboring atom was in the opposite, remote point of the orbit:
Now we have a negatively charged electron between two positively charged atomic nuclei. The nuclei of both atoms are attracted to this electron. Thus, the electron currently binds two atoms.
The distance between the nuclei of atoms is greater than the distance from each of the nuclei to the electron between them. And we remember that the force of interaction of charges is inversely proportional to the square of the distance between them. Therefore, at the moment, the force of attraction of the nuclei to the electron is greater than the mutual repulsion of the nuclei.
But electrons are constantly moving, and therefore after some time the first electron leaves the space between the nuclei, but the second electron moves there. At this moment, the role of the binder passes to the electron of the second atom (moment 3 in the figure below).
Note that at the time points shown in Figures 2 and 4, there are no electrons between the atomic nuclei. At these moments, the nuclei repel each other. For this reason, the distance between the atoms fluctuates - constantly changing in the process of rotation of electrons around the nuclei, but its average length, called the bond length, remains. The length of the bond — the distance between the nuclei of the atoms — is individual for each pair of types of atoms combined into a molecule.
The electrons of these two atoms in the formed hydrogen molecule try to be as far from each other as possible, just as they did in segments of metals. Due to this, they are synchronized - their location relative to each other on each revolution around the nuclei is approximately the same.
This is somewhat reminiscent of the collective performance of a waltz, when couples rotate at the same speed in such a way that neither the ladies nor the gentlemen will ever find themselves next to each other, but always alternate:
This article is an excerpt from the book "Understanding Chemistry . "
Holy Uncertainty and Holy Probability
Quantum theory states that it is impossible to simultaneously determine the exact place of an electron in space and its momentum (the direction and speed of its movement). Therefore, it is believed that around the nucleus of the atom there are some places (areas) in which the probability of detecting an electron is high. These regions are called electron orbitals.
This theory is not difficult to explain on a household example. Suppose you live in an apartment in which there is a bedroom, a kitchen and a bathroom. If you spend 90% of the time in the bedroom, 8% of the time in the kitchen, and 2% of the time in the bathroom, then you can consider your bedroom or kitchen as the orbital, as the probability of finding you in the bathroom is very low. After 100 observations of you at different points in time, the observer is likely to find you in 90 cases in the bedroom, and in 8 cases in the kitchen. And according to these figures will come to the conclusion about the range of your habitat.
Now about why it is impossible to simultaneously determine the place of an electron in space and its speed and direction of motion. It's even easier. The fact is that speed can be measured only on a certain segment of the distance traveled. Dividing the length of this segment by the time for which it is passed, we can find out the speed of movement. But after all, we cannot consider the location of the body a segment of space. Location is the exact coordinate of the body.
Imagine a fly in a dark room. Having lit the room with a very short flash of light, we can see the place where the fly is at the moment. But in order to understand where and at what speed it flies, we will have to turn on the light for a longer time. Then we will see a change in the position of the fly over time and will be able to estimate the speed of this change. But in this case we can no longer indicate the exact place in which the fly was at the time of measuring its speed, since during this time it has moved a certain distance. That is the whole point of the uncertainty principle.
The electrons moving around the nuclei of atoms, very quickly change the speed and direction of motion, so it is impossible to say exactly where they are at a given time and where they are going.
And in the model discussed above, the electrons move like arrows in a clock. And this can not but cause the righteous anger of adherents of the Holy Uncertainty and Holy Probability.
However, the fact that we cannot say exactly where exactly one or another electron is located, and to which of the atoms it “belongs” does not in the least change the electrostatic mechanism of binding atoms. It is impossible to connect two protons except by placing an electron between them. No probability or uncertainty can connect atoms into a molecule. And it perfectly demonstrates the molecular ion of hydrogen H2 +. In this ion, there is neither a doublet of electrons, nor compensation for the spins of paired electrons, nor overlapping of electron clouds, however, this ion exists and is stable.
Besides, one should not forget that this is just a model, and its “explanatory” possibilities are limited, as are the possibilities of any other models. For example, it (seemingly) does not explain why hydrogen atoms cannot join in long chains like H3, H4, etc.
However, it can be assumed that due to the fact that the electron orbitals in hydrogen molecules are shifted to the center of the molecule, they do not “protrude” from its ends, and therefore neighboring hydrogen molecules do not have the ability to cling to each other using the electron synchronization mechanism.
And yes, I'm aware of the existence of a model of an atom in which an electron is a probability wave located near the nucleus. But as a rule, it is difficult for a student to imagine how probability can combine atoms into molecules. Therefore, set out "on the fingers."
Connection of atoms into molecules
')
Our world does not exist in the form of individual atoms, they are somehow connected to each other. What exactly?
Take two hydrogen atoms. Each of them contains one proton and one electron, so the total charge of each of these atoms is zero.
Coulomb's law
F = k * q1 * q2 / r ^ 2
tells us that neutral bodies should not be attracted to each other
(q1 = 0, q2 = 0) .
This means that hydrogen (and any other chemical element) should exist only in the form of atoms, and never merge into molecules. In fact, hydrogen atoms are always connected in pairs. Why?
Let's take two pieces of metal, and arrange them in parallel at a short distance from each other.
Both segments contain the same number of protons and electrons, therefore, the total charge of each of them is zero. So, they have no reason for mutual attraction.
We know that in metals part of the external electrons leave their atoms and freely walk between the ions (left atoms) of the metal crystal lattice. And these electrons are distributed, on average, evenly.
Imagine that we somehow managed to move part of these free electrons to the left side of the lower metal segment. In this case, in its right side there will be a shortage of electrons.
We got the so-called dipole: the left side of the segment is negatively charged, the right side is positive. Fine. And what will happen in the upper segment? We know that like charges repel each other, and opposite ones attract each other. Consequently, the electrons of the upper segment, starting from the electric fields of the electrons of the lower segment, will go to the right side. That is, the picture of the distribution of electrons in these two segments of metals will become a mirror image:
This effect of charged objects on neighboring objects, leading to a redistribution of charges in them, is called electrostatic induction.
Now the most interesting thing: the positively charged nuclei of atoms in the left part of the upper segment are opposite to the electrons collected in the left part of the lower segment. And opposite charges attract. So, the left parts of the segments will begin to attract each other!
The same thing will happen on the right side of the segments - only mirror. And the right ends of the segments will also be attracted to each other. Wonderful, isn't it? The redistribution of charges inside one of the segments of conductors led to the mutual attraction of these two segments!
And what happens if you now move the free electrons of the lower segment to its right end? Then the free electrons of the upper segment will move to the left end. That is, by moving electrons back and forth in one of the segments, we force the electrons of a neighboring segment that is not related to the first to move! Such an effect of the movement of electrons in a single conductor on the movement of electrons in an adjacent conductor is called electrodynamic induction.
Although this does not apply to our topic, we note that we have studied in a somewhat simplified manner how the antenna and receiver work during radio transmission.
We can arrange these two pieces of metal differently - with the ends to each other:
If we are able to move the electrons, for example, to the right side of the left segment, the electrons of the right segment, starting from them, will also move to the right side of the right segment:
And in this case, these two pieces of metal will begin to attract each other, since their near ends have an opposite charge. Special attention should be paid to the fact that in the second variant of the arrangement of the segments, the force of their mutual attraction will be weaker, since only their opposite ends are attracted, while in the first variant of the arrangement of the segments, both the left and the right are attracted to each other. the ends.
But how does this relate to the union of atoms? Let's look at a hydrogen atom. It has an electron moving around the nucleus. And if there is a second hydrogen atom nearby, this electron will force the neighbor's electron to move in much the same way as they moved in our metal segments - while the electron of one of the atoms is on one side of its atomic nucleus, the next one will be forced to be on the opposite side of its atom.
Here, of course, the influence is not one-sided, but mutual - as the first electron affects the second, and the second affects the first. But the most important thing is that these two atoms will be attracted in the same way as two pieces of metal were attracted in the second variant of their mutual placement (with their ends to each other).
The essence is the same: the electrons are kept away from each other, allowing opposite charges to attract each other. Imagine that the electron of one of the atoms appeared between the nuclei of two neighboring atoms, while the electron of the neighboring atom was in the opposite, remote point of the orbit:
Now we have a negatively charged electron between two positively charged atomic nuclei. The nuclei of both atoms are attracted to this electron. Thus, the electron currently binds two atoms.
The distance between the nuclei of atoms is greater than the distance from each of the nuclei to the electron between them. And we remember that the force of interaction of charges is inversely proportional to the square of the distance between them. Therefore, at the moment, the force of attraction of the nuclei to the electron is greater than the mutual repulsion of the nuclei.
But electrons are constantly moving, and therefore after some time the first electron leaves the space between the nuclei, but the second electron moves there. At this moment, the role of the binder passes to the electron of the second atom (moment 3 in the figure below).
Note that at the time points shown in Figures 2 and 4, there are no electrons between the atomic nuclei. At these moments, the nuclei repel each other. For this reason, the distance between the atoms fluctuates - constantly changing in the process of rotation of electrons around the nuclei, but its average length, called the bond length, remains. The length of the bond — the distance between the nuclei of the atoms — is individual for each pair of types of atoms combined into a molecule.
The electrons of these two atoms in the formed hydrogen molecule try to be as far from each other as possible, just as they did in segments of metals. Due to this, they are synchronized - their location relative to each other on each revolution around the nuclei is approximately the same.
This is somewhat reminiscent of the collective performance of a waltz, when couples rotate at the same speed in such a way that neither the ladies nor the gentlemen will ever find themselves next to each other, but always alternate:
This article is an excerpt from the book "Understanding Chemistry . "
Holy Uncertainty and Holy Probability
Quantum theory states that it is impossible to simultaneously determine the exact place of an electron in space and its momentum (the direction and speed of its movement). Therefore, it is believed that around the nucleus of the atom there are some places (areas) in which the probability of detecting an electron is high. These regions are called electron orbitals.
This theory is not difficult to explain on a household example. Suppose you live in an apartment in which there is a bedroom, a kitchen and a bathroom. If you spend 90% of the time in the bedroom, 8% of the time in the kitchen, and 2% of the time in the bathroom, then you can consider your bedroom or kitchen as the orbital, as the probability of finding you in the bathroom is very low. After 100 observations of you at different points in time, the observer is likely to find you in 90 cases in the bedroom, and in 8 cases in the kitchen. And according to these figures will come to the conclusion about the range of your habitat.
Now about why it is impossible to simultaneously determine the place of an electron in space and its speed and direction of motion. It's even easier. The fact is that speed can be measured only on a certain segment of the distance traveled. Dividing the length of this segment by the time for which it is passed, we can find out the speed of movement. But after all, we cannot consider the location of the body a segment of space. Location is the exact coordinate of the body.
Imagine a fly in a dark room. Having lit the room with a very short flash of light, we can see the place where the fly is at the moment. But in order to understand where and at what speed it flies, we will have to turn on the light for a longer time. Then we will see a change in the position of the fly over time and will be able to estimate the speed of this change. But in this case we can no longer indicate the exact place in which the fly was at the time of measuring its speed, since during this time it has moved a certain distance. That is the whole point of the uncertainty principle.
The electrons moving around the nuclei of atoms, very quickly change the speed and direction of motion, so it is impossible to say exactly where they are at a given time and where they are going.
And in the model discussed above, the electrons move like arrows in a clock. And this can not but cause the righteous anger of adherents of the Holy Uncertainty and Holy Probability.
However, the fact that we cannot say exactly where exactly one or another electron is located, and to which of the atoms it “belongs” does not in the least change the electrostatic mechanism of binding atoms. It is impossible to connect two protons except by placing an electron between them. No probability or uncertainty can connect atoms into a molecule. And it perfectly demonstrates the molecular ion of hydrogen H2 +. In this ion, there is neither a doublet of electrons, nor compensation for the spins of paired electrons, nor overlapping of electron clouds, however, this ion exists and is stable.
Besides, one should not forget that this is just a model, and its “explanatory” possibilities are limited, as are the possibilities of any other models. For example, it (seemingly) does not explain why hydrogen atoms cannot join in long chains like H3, H4, etc.
However, it can be assumed that due to the fact that the electron orbitals in hydrogen molecules are shifted to the center of the molecule, they do not “protrude” from its ends, and therefore neighboring hydrogen molecules do not have the ability to cling to each other using the electron synchronization mechanism.
Source: https://habr.com/ru/post/445026/
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