Let's look at how an atom is built. Keep in mind that it will be exclusively about the models. In practice, atoms are a much more complex structure. But thanks to modern developments we have the opportunity to explain and even successfully predict the properties of chemical elements (even if not all). So, what is the scheme of the structure of the atom? What is it made of?
Planetary model of the atom
It was first proposed by the Danish physicist N. Bohr in 1913. This is the first theory of the structure of the atom, based on scientific facts. In addition, it laid the basis for modern thematic terminology. In it, the particle-electrons produce rotational motions around the atom by the same principle as the planets around the Sun. Bohr suggested that they can exist exclusively in orbits at a strictly defined distance from the nucleus. Why this is so, the scientist from the position of science could not explain, but such a model was confirmed by many experiments. To designate orbits, integers were used, starting with the one that was numbered, closest to the core. All these orbits are also called levels. The hydrogen atom has only one level, on which one electron rotates. But complex atoms have more levels. They are divided into components that combine electrons close to the energy potential. So, the second already has two sublevels - 2s and 2p. The third has already three - 3s, 3p and 3d. And so on. First, the sublevels closer to the core are populated, and then the distant ones. On each of them can be placed only a certain number of electrons. But this is not the end. Each sublevel is divided into orbitals. Let's compare with normal life. The electronic cloud of an atom is comparable to a city. Levels are streets. A sub-level is a private house or apartment. Orbital is a room. In each of them "lives" one or two electrons. All of them have specific addresses. This was the first diagram of the structure of the atom. And finally about the addresses of electrons: they are determined by sets of numbers, which are called "quantum".
The wave model of an atom
But over time, the planetary model has undergone revision. The second theory of the structure of the atom was proposed. It is more perfect and allows explaining the results of practical experiments. In place of the first came the wave model of the atom, which will be proposed by E. Schrödinger. Then it was already established that an electron can manifest itself not only as a particle, but also as a wave. And what did Schrodinger do? He applied an equation describing the motion of a wave in three-dimensional space. Thus one can find not the trajectory of the motion of an electron in an atom, but the probability of its detection at a certain point. Combining both theories is that the elementary particles are at specific levels, sublevels and orbitals. On this the similarity of models ends. I will give one example - in the wave theory, the orbital is a region where an electron can be found with a probability of 95%. All the rest of the space is 5%. But in the end it turned out that the features of the structure of atoms are depicted using the wave model, while the terminology used is shared.
The concept of probability in this case
Why was this term used? Heisenberg in 1927 formulated the uncertainty principle, which is now used to describe the motion of microparticles. It is based on their fundamental difference from ordinary physical bodies. What is it? Classical mechanics suggested that a person can observe phenomena without affecting them (observing celestial bodies). Based on the data obtained, you can calculate where the object will be at a certain point in time. But in the microcosm of business, things have to be different. So, for example, to observe the electron without affecting it, now it is not possible because the energy of the instrument and the particles are not comparable. This leads to a change in its location of the elementary particle, state, direction, speed, and other parameters. And it's pointless to talk about exact characteristics. The very principle of uncertainty tells us that it is impossible to calculate the exact trajectory of the flight of an electron around the nucleus. You can only indicate the probability of finding a particle in a certain area of space. Such a feature has the structure of atoms of chemical elements. But this should be taken into account only by scientists in practical experiments.
The composition of the atom
But let's concentrate on the whole object of consideration. So, in addition to the well-considered electronic shell, the second component of the atom is the nucleus. It consists of positively charged protons and neutral neutrons. We are all familiar with Mendeleyev's table. The number of each element corresponds to the number of protons that it contains. The number of neutrons is equal to the difference between the mass of the atom and its number of protons. There may be deviations from this rule. Then they say that there is an isotope of the element. The scheme of the structure of the atom is such that it is "surrounded" by the electron shell. The number of electrons is usually equal to the number of protons. The mass of the latter is approximately 1840 times greater than that of the first, and approximately equal to the weight of the neutron. The radius of the nucleus is about 1/200000 of the diameter of the atom. It itself has a spherical shape. This, in general, is the structure of the atoms of chemical elements. Despite the difference in mass and properties, they look about the same.
Orbits
Talking about what a scheme of the structure of the atom, you can not keep silent about them. So, there are such kinds:
- S. Have a spherical shape.
- P. Are similar to voluminous figures or a spindle.
- D and f. Have a complex form, which is difficult to describe a formal language.
An electron of each type can be found with a probability of 95% in the territory of the corresponding orbitals. The presented information should be treated calmly, because it is, rather, an abstract mathematical model, rather than a physical real state of affairs. But with all this, it has a good predictive power with respect to the chemical properties of atoms and even molecules. The further from the core the level is located, the more electrons can be placed on it. So, the number of orbitals can be calculated using a special formula: x 2 . Here x is equal to the number of levels. And since up to two electrons can be placed on the orbitals, in the final analysis the formula for their numerical search will look like this: 2x2.
Orbits: technical data
If we talk about the structure of the fluorine atom, it will have three orbitals. All of them will be filled. The energy of the orbitals within the same sublevel is the same. To mark them, add a layer number: 2s, 4p, 6d. We return to the conversation about the structure of the fluorine atom. He will have two s- and one p-sublevels. He has nine protons and the same number of electrons. First one s-level. These are two electrons. Then the second s-level. Two more electrons. And 5 fill the p-level. That's his structure. After reading the next sub-heading, you can do the necessary actions yourself and see for yourself. If we talk about the physical properties of halogens, which include fluorine, it should be noted that they, although in the same group, are completely different in their characteristics. So, their boiling point ranges from -188 to 309 degrees Celsius. So why they were united? All thanks to chemical properties. All halogens, and most of all fluorine have the highest oxidizing ability. They react with metals and without problems can self-ignite at room temperature.
How are the orbits filled?
What are the rules and principles of electrons? We offer you to familiarize yourself with three main ones, the wording of which was simplified for a better understanding:
- The principle of least energy. Electrons tend to fill orbitals in order of increasing their energy.
- The Pauli principle. On one orbital, no more than two electrons can be located.
- The rule of Hund. Within one sublevel, electrons fill first free orbitals, and only then form pairs.
The periodic system of Mendeleyev will help in the filling, and the structure of the atom in this case will become more clear in terms of the image. Therefore, in the practical work with the construction of schemes of elements, it is necessary to keep it at hand.
Example
In order to generalize all that has been said within the framework of the article, it is possible to make a sample of how the electrons of the atom are distributed over their levels, sublevels and orbitals (that is, what is the level configuration). It can be depicted as a formula, an energy diagram or as a scheme of layers. Here there are very good illustrations, which, upon close examination, help to understand the structure of the atom. So, first the first level is filled. In it there is only one sublevel, in which there is only one orbital. All levels are filled in sequence, starting with a smaller one. First, within one sublevel, one electron is placed on each orbital. Then pairs are created. And if there are free ones, switching to another subject of filling takes place. And now you can independently know what the structure of the nitrogen atom or fluorine (which was considered earlier). Initially, it can be a little difficult, but you can navigate through the pictures. Let's look at the structure of the nitrogen atom for clarity. It has 7 protons (together with the neutrons that make up the nucleus) and the same number of electrons (which make up the electron shell). First, fill the first s-level. It has 2 electrons. Then comes the second s-level. There are also 2 electrons on it. And the other three are placed on the p-level, where each of them occupies one orbitals.
Conclusion
As you can see, the structure of the atom is not such a difficult subject (if one approaches it from the standpoint of the school chemistry course, of course). And to understand this topic is not difficult. Finally I want to inform you about some features. For example, speaking of the structure of the oxygen atom, we know that it has eight protons, and 8-10 neutrons. And since everything in nature tends to equilibrium, two oxygen atoms form a molecule where two unpaired electrons form a covalent bond. Similarly, another stable oxygen molecule - ozone (O 3 ) - is formed. Knowing the structure of the oxygen atom, it is possible to correctly formulate oxidation reaction formulas in which the most abundant substance participates on the Earth.