Let's look at how an atom is built. Keep in mind that we will only talk about models. In practice, atoms are a much more complex structure. But thanks to modern developments, we are able to explain and even successfully predict the properties of chemical elements (even if not all). So, what is the structure of an atom? What is it "made" of?
Planetary model of the atom
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, she laid the foundation for modern thematic terminology. In it, electron-particles produce rotational movements around the atom in the same way as the planets around the Sun. Bohr suggested that they can exist only in orbits located at a strictly defined distance from the nucleus. Why exactly, the scientist from the position of science could not explain, but such a model was confirmed by many experiments. Integer numbers were used to designate the orbits, starting with the unit that was numbered closest to the nucleus. 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 unite electrons that are close in energy potential. So, the second one already has two sublevels - 2s and 2p. The third one already has three - 3s, 3p and 3d. Etc. First, the sublevels closer to the nucleus are “populated”, and then the distant ones. Each of them can only hold a certain number of electrons. But this is not the end. Each sublevel is divided into orbitals. Let's make a comparison with ordinary life. The electron cloud of an atom is comparable to a city. Levels are streets. Sublevel - a private house or apartment. Orbital is a room. 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".
Wave model of the atom
But over time, the planetary model has been revised. A second theory of the structure of the atom was proposed. It is more perfect and allows to explain the results of practical experiments. The wave model of the atom, proposed by E. Schrödinger, replaced the first one. Then it was already established that an electron can manifest itself not only as a particle, but also as a wave. What did Schrödinger do? He applied an equation describing the motion of a wave in three-dimensional space. Thus, one can find not the trajectory of the electron in the atom, but the probability of its detection at a certain point. Both theories are united by the fact that elementary particles are located onspecific levels, sublevels and orbitals. This is where the similarity of the models ends. I will give one example - in wave theory, an orbital is a region where it will be possible to find an electron with a probability of 95%. The rest of space accounts for 5%. But in the end it turned out that the structural features of atoms are depicted using a wave model, despite the fact that the terminology is used in a general way.
The concept of probability in this case
Why was this term used? Heisenberg formulated the uncertainty principle in 1927, 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 assumed that a person can observe phenomena without affecting them (observation of celestial bodies). Based on the received data, it is possible to calculate where the object will be at a certain point in time. But in the microcosm, things are necessarily different. So, for example, to observe an electron without influencing it is now not possible due to the fact that the energies of the instrument and the particle are incomparable. This leads to the fact that its location of an elementary particle, state, direction, speed of movement and other parameters change. And it makes no sense to talk about the exact characteristics. The uncertainty principle itself tells us that it is impossible to calculate the exact trajectory of the electron around the nucleus. You can only specify the probability of finding a particle in a certain areaspace. This is the peculiarity of the structure of atoms of chemical elements. But this should be taken into account exclusively by scientists in practical experiments.
Composition of an atom
But let's focus on the whole subject matter. So, in addition to the well-considered electron shell, the second component of the atom is the nucleus. It consists of positively charged protons and neutral neutrons. We are all familiar with the periodic table. The number of each element corresponds to the number of protons that it has. The number of neutrons is equal to the difference between the mass of an atom and its number of protons. There may be deviations from this rule. Then they say that an isotope of the element is present. The structure of an atom is such that it is "surrounded" by an electron shell. The number of electrons is usually equal to the number of protons. The mass of the latter is about 1840 times greater than that of the former, and is approximately equal to the weight of the neutron. The radius of the nucleus is about 1/200,000 of the diameter of an atom. He himself has a spherical shape. This is, in general, the structure of atoms of chemical elements. Despite the difference in mass and properties, they look about the same.
Orbits
Speaking about what the scheme of the structure of the atom is, one cannot remain silent about them. So, there are these types:
- s. They are spherical.
- p. They look like voluminous figure eights or spindles.
- d and f. They have a complex shape that is difficult to describe in formal language.
Electron of each type can be found with a probability of 95% in the territorycorresponding orbital. The presented information must be taken calmly, since it is rather an abstract mathematical model than a physical real state of affairs. But with all this, it has good predictive power regarding the chemical properties of atoms and even molecules. The farther from the nucleus the level is located, the more electrons can be placed on it. So, the number of orbitals can be calculated using a special formula: x2. Here x is equal to the number of levels. And since up to two electrons can be placed on the orbital, the final 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 orbitals within the same sublevel is the same. To designate them, add the layer number: 2s, 4p, 6d. We return to the conversation about the structure of the fluorine atom. It will have two s- and one p-sublevel. It 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 fills the p-level. Here is his structure. After reading the following subheading, you can do the necessary actions yourself and see for yourself. If we talk about the physical properties of halogens, which include fluorine, then it should be noted that they, although in the same group, completely differ in their characteristics. So, their boiling point ranges from -188 to 309degrees Celcius. So why are they merged? All thanks to the chemical properties. All halogens, and to the greatest extent fluorine, have the highest oxidizing power. They react with metals and can spontaneously ignite at room temperature without any problems.
How are orbits filled?
By what rules and principles are electrons arranged? We suggest that you familiarize yourself with the three main ones, the wording of which has been simplified for a better understanding:
- Principle of least energy. Electrons tend to fill orbitals in order of increasing energy.
- Pauli principle. One orbital cannot contain more than two electrons.
- Hund's rule. Within one sublevel, electrons first fill free orbitals, and only then form pairs.
The periodic system of Mendeleev will help in filling, and the structure of the atom in this case will become more understandable in terms of the image. Therefore, in practical work with the construction of circuits of elements, it is necessary to keep it at hand.
Example
In order to summarize everything said in the article, you can make a sample of how the electrons of an atom are distributed over their levels, sublevels and orbitals (that is, what is the level configuration). It can be shown as a formula, an energy diagram, or as a layer diagram. There are very good illustrations here, which, upon close examination, help to understand the structure of the atom. So, the first level is filled first. It hasonly one sublevel, in which there is only one orbital. All levels are filled sequentially, starting with the smallest. First, within one sublevel, one electron is placed in each orbital. Then pairs are created. And if there are free ones, it switches to another filling subject. And now you can independently find out what is the structure of the nitrogen or fluorine atom (which was considered earlier). It can be a bit tricky at first, but you can navigate by looking at the pictures. For clarity, let's look at the structure of the nitrogen atom. It has 7 protons (together with neutrons that make up the nucleus) and the same number of electrons (which make up the electron shell). The first s-level is filled first. It has 2 electrons. Then comes the second s-level. It also has 2 electrons. And the other three are placed at the p-level, where each of them occupies one orbital.
Conclusion
As you can see, the structure of the atom is not such a difficult topic (if you approach it from the perspective of a school chemistry course, of course). And it is not difficult to understand this topic. Finally, I would like to inform you about some features. For example, speaking about the structure of the oxygen atom, we know that it has eight protons and 8-10 neutrons. And since everything in nature tends to balance, two oxygen atoms form a molecule, where two unpaired electrons form a covalent bond. Similarly, another stable oxygen molecule is formed - ozone (O3). Knowing the structure of the oxygen atom, it is possible to correctly formulate oxidation reactions, inwhich involves the most common substance on Earth.
