Vita Pylypiv

Electronic configuration, also called electronic structure, the arrangement of electrons in energy levels around an atomic nucleus. According to the older shell atomic model, electrons occupy several levels from the first shell nearest the nucleus, K, through the seventh shell, Q, farthest from the nucleus. In terms of a more refined, quantum-mechanical model, the K–Q shells are subdivided into a set of orbitals (see orbital), each of which can be occupied by no more than a pair of electrons. The table below lists the number of orbitals available in each of the first four shells.

The electronic configuration of an atom in the shell atomic model may be expressed by indicating the number of electrons in each shell beginning with the first. For example, sodium (atomic number 11) has its 11 electrons distributed in the first three shells as follows: the K and L shells are completely filled, with 2 and 8 electrons respectively, while the M shell is only parti ally filled with one electron.

The electronic configuration of an atom in the quantum-mechanical model is stated by listing the occupied orbitals, in order of filling, with the number of electrons in each orbital indicated by superscript. In this notation, the electronic configuration of sodium would be 1s22s22p63s1, distributed in the orbitals as 2-8-1. Often, a shorthand method is used that lists only those electrons in excess of the noble gas configuration immediately preceding the atom in the periodic table. For example, sodium has one 3s electron in excess of the noble gas neon (chemical symbol Ne, atomic number 10), and so its shorthand notation is [Ne]3s1.

Elements in the same group in the periodic table have similar electronic configurations. For example, the elements lithium, sodium, potassium, rubidium, cesium, and francium (the alkali metals of Group I) all have electronic configurations showing one electron in the outermost (most loosely bound) s orbital. This so-called valence electron is responsible for the similar chemical properties shared by the above-mentioned alkali elements in Group I: bright metallic lustre, high reactivity, and good thermal conductivity.

Most bertolides among crystalline compounds of non-molecular structure: oxides, chalcogenides and other binary compounds of ionic structure; ternary compounds such as oxide bronzes.

Bertolides are usually considered as solid solutions of the excess component (atoms, ions) in the basic, stoichiometric, substance. The values ​​of their maximum solubility limit the region of homogeneity - the region of stable existence of the nonstoichiometric phase. The solubility of excess components in various compounds ranges from thousandths of a percent to several percent. Examples:

nonstoichiometric phase TiO is stable in the range of TiO1,25 — TiO0,65,

Oxygen deficiency in ZrO2 at 1200 ° C can reach a molar 14% (corresponding to the formula ZrO2 – x with 0 ≤ x <0.28),

near the melting point of PbO, the solubility of Pb in it does not exceed 10−2%, Oxygen - 10−3% (which corresponds to the formula PbO1-x from -0.001 <x <0.01).

Often non-stoichiometric are compounds in which the metal is in the intermediate stage of oxidation. Here, the formation of a solid solution is facilitated by the fact that part of the metal ions changes the degree of oxidation. For example, in the case of an excess of oxygen in titanium (II) oxide TiO1 + x part of the titanium ions increases the degree of oxidation.

Cationic defect in FeO crystal

The formation of bertolides is associated with the violation of the periodicity of the crystal lattice and the appearance of defects that determine the most important properties of bertolides - electrophysical, optical, magnetic and so on. Such defects are often the centers of color, the intensity of which is associated with the magnitude of the deviation from the stoichiometric composition. For example, violation of stoichiometry in the direction of excess metal turns colorless BaO crystals into blue, NaCl - into yellow, KCl - into purple. Sodium tungsten bronze as it decreases in sodium changes color from golden yellow (NaWO3) to dark blue-green (Na0.3WO3), passing through red and purple.

What Is A Crystal Lattice?

Do you know what common table salt (NaCl) and a beautiful, shiny diamond have in common? I know what you're thinking - how on earth could the salt on your french fries have anything in common with the expensive diamonds found in jewelry? Well, based on their structure, they are both solid objects that contain tiny crystals interlocking together.

In chemistry, crystals are a type of solid material composed of atoms or groups of atoms that are arranged in a three-dimensional pattern that is very ordered. In a crystal, the groups of atoms are repetitive at evenly spaced intervals, all maintaining their orientation to one another. In other words, the geometric shape of a crystal is highly symmetrical. When you see the word 'symmetrical,' think about the perfect proportion and balance of these atoms in a crystal. Now that we know what a crystal is, and that is can be found inside our table salt and a sparkly diamond, let's look at crystal lattices.

A crystal lattice is the arrangement of these atoms, or groups of atoms, in a crystal. These atoms or groups of atoms are commonly referred to as points within a crystal lattice site. Thus, think of a crystal lattice site as containing a series of points arranged in a specific pattern with high symmetry. Note that these points don't tell you the position of an atom in a crystal. They are simply points 'in space' oriented in such a way to build a lattice structure.

Helium gas (98.2 percent pure) is isolated from natural gas by liquefying the other components at low temperatures and under high pressures. Adsorption of other gases on cooled, activated charcoal yields 99.995 percent pure helium. Some helium is supplied from liquefaction of air on a large scale; the amount of helium obtainable from 1,000 tons (900 metric tons) of air is about 112 cubic feet (3.17 cubic metres), as measured at room temperature and at normal atmospheric pressure.Helium is used as an inert-gas atmosphere for welding metals such as aluminum; in rocketpropulsion (to pressurize fuel tanks, especially those for liquid hydrogen, because only helium is still a gas at liquid-hydrogen temperature); in meteorology (as a lifting gas for instrument-carrying balloons); in cryogenics (as a coolant because liquid helium is the coldest substance); and in high-pressure breathing operations (mixed with oxygen, as in scuba diving and caisson work, especially because of its low solubility in the bloodstream). Meteorites and rocks have been analyzed for helium content as a means of dating

Osmoloda is a village in the Perehinsky settlement community of the Kalush district of the Ivano-Frankivsk region. Located in the Gorgan massif. The southernmost settlement of the district. Area: 3,564 km² Population density: 16.55 people / km² Region: Ivano-Frankivsk region District / City Council: Kalush district

Production and uses

Production and uses

Production and uses

A liquid mixture of the two isotopes helium-3 and helium-4 separates at temperatures below about 0.8 K (−272.4 °C, or −458.2 °F) into two layers. One layer is practically pure helium-3; the other is mostly helium-4 but retains about 6 percent helium-3 even at the lowest temperatures achieved. The dissolution of helium-3 in helium-4 is accompanied by a cooling effect that has been used in the construction of cryostats (devices for production of very low temperatures) that can attain—and maintain for days—temperatures as low as 0.01 K (−273.14 °C, or −459.65 °F).

A liquid mixture of the two isotopes helium-3 and helium-4 separates at temperatures below about 0.8 K (−272.4 °C, or −458.2 °F) into two layers. One layer is practically pure helium-3; the other is mostly helium-4 but retains about 6 percent helium-3 even at the lowest temperatures achieved.

A liquid mixture of the two isotopes helium-3 and helium-4 separates at temperatures below about 0.8 K (−272.4 °C, or −458.2 °F) into two layers.

Helium-4 is unique in having two liquid forms. The normal liquid form is called helium I and exists at temperatures from its boiling point of 4.21 K (−268.9 °C) down to about 2.18 K (−271 °C). Below 2.18 K, thermal conductivity of helium-4 becomes more than 1,000 times greater than that of copper.This liquid form is called helium II to distinguish it from normal liquid helium I. Helium II exhibits the property called superfluidity: its viscosity, or resistance to flow, is so low that it has not been measured. This liquid spreads in a thin film over the surface of any substance it touches, and this film flows without friction even against the force of gravity. By contrast, the less plentiful helium-3 forms three distinguishable liquid phases of which two are superfluids. Superfluidity in helium-4 was discovered by the Russian physicist Pyotr Leonidovich Kapitsa in the mid-1930s, and the same phenomenon in helium-3 was first observed by Douglas D. Osheroff, David M. Lee, and Robert C. Richardson of the United States in 1972.

Helium-4 is unique in having two liquid forms. The normal liquid form is called helium I and exists at temperatures from its boiling point of 4.21 K (−268.9 °C) down to about 2.18 K (−271 °C). Below 2.18 K, thermal conductivity of helium-4 becomes more than 1,000 times greater than that of copper.This liquid form is called helium II to distinguish it from normal liquid helium I. Helium II exhibits the property called superfluidity: its viscosity, or resistance to flow, is so low that it has not been measured. This liquid spreads in a thin film over the surface of any substance it touches, and this film flows without friction even against the force of gravity. By contrast, the less plentiful helium-3 forms three distinguishable liquid phases of which two are superfluids.

Helium-4 is unique in having two liquid forms. The normal liquid form is called helium I and exists at temperatures from its boiling point of 4.21 K (−268.9 °C) down to about 2.18 K (−271 °C). Below 2.18 K, thermal conductivity of helium-4 becomes more than 1,000 times greater than that of copper.This liquid form is called helium II to distinguish it from normal liquid helium I. Helium II exhibits the property called superfluidity: its viscosity, or resistance to flow, is so low that it has not been measured. This liquid spreads in a thin film over the surface of any substance it touches, and this film flows without friction even against the force of gravity.

Helium-4 is unique in having two liquid forms. The normal liquid form is called helium I and exists at temperatures from its boiling point of 4.21 K (−268.9 °C) down to about 2.18 K (−271 °C). Below 2.18 K, thermal conductivity of helium-4 becomes more than 1,000 times greater than that of copper.This liquid form is called helium II to distinguish it from normal liquid helium I. Helium II exhibits the property called superfluidity: its viscosity, or resistance to flow, is so low that it has not been measured.

Helium-4 is unique in having two liquid forms. The normal liquid form is called helium I and exists at temperatures from its boiling point of 4.21 K (−268.9 °C) down to about 2.18 K (−271 °C). Below 2.18 K, thermal conductivity of helium-4 becomes more than 1,000 times greater than that of coppercopper.This liquid form is called helium II to distinguish it from normal liquid helium I.