The structure of the atom. Energy levels of the atom. Protons, neutrons, electrons
The name "atom" is translated from Greek as "indivisible". All around us - solids, liquids and air - are built of billions of these particles.
The appearance of the version about the atom
For the first time about atoms it became known in the V century beforeAD, when the Greek philosopher Democritus suggested that matter consists of moving tiny particles. But then there was no way to check the version of their existence. And although no one could see these particles, the idea was discussed, because only so scientists could explain the processes taking place in the real world. Therefore, they believed in the existence of microparticles long before the time when they were able to prove this fact.
Only in the XIX century. they began to be analyzed as the smallest components of chemical elements that have specific properties of atoms-the ability to join compounds with others in a strictly prescribed quantity. At the beginning of the XX century it was believed that atoms are the minimal particles of matter, until it was proved that they consist of even smaller units.
What is the chemical element of?
The atom of the chemical element is microscopicbuilding brick of matter. The determining factor of this microparticle is the molecular mass of the atom. Only the discovery of the periodic law of Mendeleev justified that their species represent various forms of a single matter. They are so small that they can not be seen using conventional microscopes, only the most powerful electronic devices. For comparison, the hair on the man's hand is a million times wider.
The electronic structure of an atom has a nucleus consisting offrom neutrons and protons, as well as electrons that make revolutions around the center in permanent orbits, like planets around their stars. All of them are fastened by an electromagnetic force, one of the four main in the universe. Neutrons are particles with a neutral charge, protons are positive, and electrons - negative. The latter are attracted to positively charged protons, so they tend to stay in orbit.
The structure of the atom
In the central part there is a core fillingthe minimum part of the whole atom. But research shows that almost the entire mass (99.9%) is located exactly in it. Each atom contains protons, neutrons, electrons. The number of rotating electrons in it equals the positive central charge. Particles with the same charge of the nucleus Z, but different atomic mass A and the number of neutrons in the nucleus N are called isotopes, but with the same A and different Z and N isobars. Electron is the minimum particle of matter with a negative electric charge e = 1.6 · 10-19 coulomb. The ion charge determines the amount of lost or added electrons. The process of metamorphosis of a neutral atom into a charged ion is called ionization.
New version of the atomic model
Physicists have discovered to date many other elementary particles. The electronic structure of the atom has a new version.
It is believed that protons and neutrons, no matter howthey were not small, they consist of the smallest particles, which are called quarks. They constitute a new model for constructing an atom. As earlier scientists collected evidence for the existence of the previous model, so today they try to prove the existence of quarks.
RTM - the device of the future
Modern scientists can see on the monitorcomputer, atomic particles of matter, and also to move them over the surface, using a special tool called a scanning tunneling microscope (RTM).
itcomputerizedtool with a tip that is verygently moves near the surface of the material. When the tip moves, electrons move through the gap between the tip and the surface. Although the material looks completely smooth, in fact it is uneven at the atomic level. The computer makes a map of the surface of the substance, creating an image of its particles, and scientists, thus, can see the properties of the atom.
Negatively charged ions circulate around the nucleusat a sufficiently large distance. The structure of the atom is such that the whole is really neutral and has no electric charge, because all its particles (protons, neutrons, electrons) are in balance.
A radioactive atom is an element that can beeasy to split. Its center consists of many protons and neutrons. The exception is only a diagram of the hydrogen atom, which has one single proton. The nucleus is surrounded by a cloud of electrons, it is their attraction that makes it rotate around the center. Protons repel each other with the same charge.
This is not a problem for most small particles,in which there are several. But some of them are unstable, especially for large-sized ones, such as uranium, which has 92 protons. Sometimes his center does not stand such a load. They are called radioactive because they throw several particles from their nucleus. After the unstable core got rid of the protons, the remaining form a new daughter. It can be stable depending on the number of protons in the new core, and can be divided further. This process lasts until there is a stable child kernel.
Properties of atoms
The physico-chemical properties of an atom naturally vary from one element to another. They are determined by the following basic parameters.
Atomic mass. Since the main place of the microparticle is occupied by protons and neutrons, the sum of them is determined by the number expressed in atomic mass units (amu). Formula: A = Z + N.
Atomic radius. The radius depends on the location of the element in the Mendeleyev system, the chemical bond, the number of neighboring atoms, and the quantum-mechanical effect. The radius of the nucleus is one hundred thousand times less than the radius of the element itself. The structure of an atom can lose electrons and turn into a positive ion or add electrons, and become a negative ion.
In the Mendeleev periodic system, anythe chemical element takes its place. In the table, the size of the atom increases when moving from top to bottom and decreases when moving from left to right. Following this, the smallest element is helium, and the largest element is cesium.
Valence. The outer electronic shell of an atom is called valence, and the electrons in it are appropriately named valence electrons. Their number determines how an atom combines with the rest by chemical bonding. The method of creating the latter microparticles tries to fill their outer valence shells.
Gravitation, attraction is the power that holdsplanets in orbit, because of it, objects released from the hands fall to the floor. A person more notice gravity, but the electromagnetic action is many times more powerful. The force that attracts (or repels) charged particles in an atom is 1,000,000,000,000,000,000,000,000,000,000,000,000,000 times more powerful than gravity in it. But in the center of the nucleus there is an even more powerful force capable of holding protons and neutrons together.
Reactions in nuclei create energy both in nuclearreactors, where the atoms are split. The heavier the element, the more of its atoms are built from more particles. If we add the total number of protons and neutrons in the element, we know its mass. For example, Uranus, the heaviest element available in nature, has an atomic mass of 235 or 238.
Fission of an atom into levels
The energy levels of an atom are the magnitudespace around the nucleus, where the electron is in motion. In total there are 7 orbitals corresponding to the number of periods in the periodic table. The more distant the location of the electron from the nucleus, the more significant energy reserve it owns. The period number indicates the number of atomic orbitals around its core. For example, Potassium is an element of the 4th period, hence, it has 4 energy levels of the atom. The number of the chemical element corresponds to its charge and the number of electrons around the nucleus.
Atom - the source of energy
Probably the most famous scientific formulaIt was discovered by the German physicist Einstein. She argues that the mass is nothing more than a form of energy. Based on this theory, you can turn matter into energy and calculate by the formula how much it can be obtained. The first practical result of this transformation were atomic bombs, which were first tested in the Los Alamos desert (USA), and then exploded over Japanese cities. And although only the seventh part of the explosive turned into energy, the destructive force of the atomic bomb was terrible.
In order for the nucleus to release its energy, itmust be destroyed. To split it, it is necessary to act on the neutron outside. Then the nucleus breaks up into two other, lighter ones, while ensuring a huge energy release. Decay leads to the release of other neutrons, and they continue to split other nuclei. The process turns into a chain reaction, resulting in a huge amount of energy.
Pros and cons of using nuclear reaction in our time
The destructive force that is liberated in the transformation of matter, humanity is trying to tame at nuclear power plants. Here the nuclear reaction does not take place in the form of an explosion, but as a gradual return of heat.
The production of nuclear energy has its advantages andminuses. According to scientists, in order to maintain our civilization at a high level, it is necessary to use this huge source of energy. But it should also be taken into account that even the most advanced developments can not guarantee the complete safety of nuclear power plants. In addition, radioactive waste received in the process of energy production in case of improper storage can affect our descendants for tens of thousands of years.
After the Chernobyl accident, more and morepeople consider the production of nuclear energy is very dangerous for humanity. The only safe powerhouse of this kind is the Sun with its nuclear energy of enormous power. Scientists are developing all sorts of models of solar cells, and, perhaps, in the near future, mankind can provide itself with safe nuclear energy.