For a long time, many properties of matter remained a secret for researchers. Why do some substances conduct electricity well, while others do not? Why does iron gradually degrade under the influence of the atmosphere, and noble metals are perfectly preserved for thousands of years? Many of these questions were answered after a person became aware of the structure of an atom: its structure, the number of electrons in each electron layer. Moreover, the development of even the very foundations of the structure of atomic nuclei has opened up a new era for the world.
What elements are built up of the elementary brick of matter, how do they interact with each other, what can we learn to use from this?
Atom structure in modern science
Currently, most scientists tend to adhere to a planetary model of the structure of matter. According to this model, in the center of each atom is a nucleus that is tiny even compared to an atom (it is tens of thousands of times smaller than a whole atom). But you can’t say the same about the mass of the nucleus. Almost the entire mass of an atom is concentrated precisely in the nucleus. The core is positively charged.
Electrons rotate around the nucleus in various orbits, not circular, as in the case of the planets of the solar system, but volumetric (spheres and volumetric eights). The number of electrons in an atom is numerically equal to the charge of the nucleus. But to consider an electron as a particle that moves along some trajectory is very difficult.
Its orbit is tiny, and the speed is almost like that of a light beam, therefore it is more correct to consider the electron together with its orbit as some kind of negatively charged sphere.
Atomic family members
All atoms are composed of 3 constituent elements: protons, electrons and neutrons.
Proton is the main building material of the nucleus. Its weight is equal to the atomic unit (mass of the hydrogen atom) or 1.67 ∙ 10 -27 kg in the SI system. The particle is positively charged, and its charge is taken as unity in the system of elementary electric charges.
The neutron is the twin of the proton in mass, but not charged at all.
Two of the above particles are called nuclides.
An electron is the opposite of a proton in charge (elementary charge is −1). But the electron pumped up by weight, its mass is only 9.12 ∙ 10 -31 kg, which is almost 2 thousand times lighter than a proton or neutron.
How to "make out"
How could one make out the structure of an atom, even if the most modern technical means do not allow and in the near future will not allow obtaining images of its constituent particles. How did scientists find out the number of protons, neutrons and electrons in the nucleus and their location?
The assumption of the planetary arrangement of atoms was made on the basis of the results of the bombardment of thin metal foil by various particles. The figure clearly shows how various elementary particles interact with matter.
The number of electrons passing through the metal in the experiments was zero. This is explained simply: negatively charged electrons repel from the electron shells of the metal, which also have a negative charge.
The proton beam (charge +) passed through the foil, but with "losses". Part of it was repelled by nuclei that got in the way (the probability of such hits is very small), part deviated from the original trajectory, flying too close to one of the nuclei.
The most "effective" in terms of overcoming the metal were neutrons. A neutrally charged particle was lost only in the event of a direct collision with the nucleus of a substance, while 99.99% of neutrons successfully passed through the thickness of the metal. By the way, the size of the nuclei of certain chemical elements was calculated precisely on the basis of the number of neutrons at the input and not the output.
Based on the data obtained, the currently dominant theory of the structure of matter was constructed, which successfully explains most of the issues.
What and how much
The number of electrons in an atom depends on the sequence number. So, in an atom of ordinary hydrogen there is only one proton. Around the same orbit circling a single electron. The next element of the periodic table - helium is a little more complicated. Its nucleus consists of two protons and two neutrons and thus has an atomic mass of 4.
With the growth of the serial number, the size and mass of the atom grow. The serial number of the chemical element in the periodic table corresponds to the charge of the nucleus (the number of protons in it). The number of electrons in an atom is equal to the number of protons. So, a lead atom (serial number 82) has 82 protons in its nucleus. In orbits around the nucleus are 82 electrons. To calculate the number of neutrons in the nucleus, it is enough to subtract the number of protons from the atomic mass:
207 - 82 = 125.
Why are they always equally divided
Any system in our universe strives for stability. In relation to an atom, this is expressed in its neutrality. If we imagine for a second that all atoms in the Universe without exception have one charge or another of different sizes with different signs, we can imagine how chaos would come in the world.
But since the number of protons and electrons in an atom is equal, the total charge of each "brick" is zero.
The number of neutrons in an atom is an independent quantity. Moreover, the atoms of the same chemical element can have a different number of these particles with zero charge. Example:
- 1 proton + 1 electron + 0 neutrons = hydrogen (atomic mass 1);
- 1 proton + 1 electron + 1 neutron = deuterium (atomic mass 2);
- 1 proton + 1 electron + 2 neutrons = tritium (atomic mass 3).
In this case, the number of electrons in an atom does not change, the atom remains neutral, and its mass changes. Such variations of chemical elements are commonly called isotopes.
Is the atom always neutral
No, the number of electrons in an atom is not always equal to the number of protons. If an atom or two could not be taken away from an atom for a time, there would not have existed such a thing as electroplating. Atom, like any matter, can be affected.
Under the influence of a sufficiently strong electric field from the outer layer of an atom, one or more electrons can “fly away”. In this case, a particle of the substance ceases to be neutral and is called an ion. It can move in a gas or liquid medium, transferring an electric charge from one electrode to another. Thus, they store electric charge in storage batteries, and also apply the thinnest films of some metals to the surfaces of others (gilding, silvering, chrome plating, nickel plating, etc.).
The number of electrons is also unstable in metals - conductors of electric current. The electrons of the outer layers seem to walk from atom to atom, transferring electrical energy through a conductor.