Length and distance converter Mass converter Converter of volume measures of bulk products and food products Area converter Converter of volume and units of measurement in culinary recipes Temperature converter Converter of pressure, mechanical stress, Young's modulus Converter of energy and work Converter of power Converter of force Converter of time Linear speed converter Flat angle Converter thermal efficiency and fuel efficiency Converter of numbers in various number systems Converter of units of measurement of quantity of information Currency rates Women's clothing and shoe sizes Men's clothing and shoe sizes Angular velocity and rotation frequency converter Acceleration converter Angular acceleration converter Density converter Specific volume converter Moment of inertia converter Moment of force converter Torque converter Specific heat of combustion converter (by mass) Energy density and specific heat of combustion converter (by volume) Temperature difference converter Coefficient of thermal expansion converter Thermal resistance converter Thermal conductivity converter Specific heat capacity converter Energy exposure and thermal radiation power converter Heat flux density converter Heat transfer coefficient converter Volume flow rate converter Mass flow rate converter Molar flow rate converter Mass flow density converter Molar concentration converter Mass concentration in solution converter Dynamic (absolute) viscosity converter Kinematic viscosity converter Surface tension converter Vapor permeability converter Water vapor flow density converter Sound level converter Microphone sensitivity converter Converter Sound Pressure Level (SPL) Sound Pressure Level Converter with Selectable Reference Pressure Luminance Converter Luminous Intensity Converter Illuminance Converter Computer Graphics Resolution Converter Frequency and Wavelength Converter Diopter Power and Focal Length Diopter Power and Lens Magnification (×) Converter electric charge Linear charge density converter Surface charge density converter Volume charge density converter Electric current converter Linear current density converter Surface current density converter Electric field strength converter Electrostatic potential and voltage converter Electrical resistance converter Electrical resistivity converter Electrical conductivity converter Electrical conductivity converter Electrical capacitance Inductance Converter American Wire Gauge Converter Levels in dBm (dBm or dBm), dBV (dBV), watts, etc. units Magnetomotive force converter Magnetic field strength converter Magnetic flux converter Magnetic induction converter Radiation. Ionizing radiation absorbed dose rate converter Radioactivity. Radioactive decay converter Radiation. Exposure dose converter Radiation. Absorbed dose converter Decimal prefix converter Data transfer Typography and image processing unit converter Timber volume unit converter Calculation of molar mass Periodic table of chemical elements by D. I. Mendeleev
Chemical formula
Molar mass of TcCl 4, technetium(IV) chloride 239.812 g/mol
Mass fractions of elements in the compound
Using the Molar Mass Calculator
- Chemical formulas must be entered case sensitive
- Subscripts are entered as regular numbers
- The dot on the midline (multiplication sign), used, for example, in the formulas of crystalline hydrates, is replaced by a regular dot.
- Example: instead of CuSO₄·5H₂O in the converter, for ease of entry, the spelling CuSO4.5H2O is used.
Electric potential and voltage
Molar mass calculator
Mole
All substances are made up of atoms and molecules. In chemistry, it is important to accurately measure the mass of substances that react and are produced as a result. By definition, the mole is the SI unit of quantity of a substance. One mole contains exactly 6.02214076×10²³ elementary particles. This value is numerically equal to Avogadro's constant N A when expressed in units of mol⁻¹ and is called Avogadro's number. Amount of substance (symbol n) of a system is a measure of the number of structural elements. A structural element can be an atom, molecule, ion, electron, or any particle or group of particles.
Avogadro's constant N A = 6.02214076×10²³ mol⁻¹. Avogadro's number is 6.02214076×10²³.
In other words, a mole is an amount of substance equal in mass to the sum of the atomic masses of atoms and molecules of the substance, multiplied by Avogadro's number. The unit of quantity of a substance, the mole, is one of the seven basic SI units and is symbolized by the mole. Since the name of the unit and its symbol are the same, it should be noted that the symbol is not declined, unlike the name of the unit, which can be declined according to the usual rules of the Russian language. One mole of pure carbon-12 is equal to exactly 12 g.
Molar mass
Molar mass is a physical property of a substance, defined as the ratio of the mass of this substance to the amount of substance in moles. In other words, this is the mass of one mole of a substance. The SI unit of molar mass is kilogram/mol (kg/mol). However, chemists are accustomed to using the more convenient unit g/mol.
molar mass = g/mol
Molar mass of elements and compounds
Compounds are substances consisting of different atoms that are chemically bonded to each other. For example, the following substances, which can be found in any housewife’s kitchen, are chemical compounds:
- salt (sodium chloride) NaCl
- sugar (sucrose) C₁₂H₂₂O₁₁
- vinegar (acetic acid solution) CH₃COOH
The molar mass of a chemical element in grams per mole is numerically the same as the mass of the element's atoms expressed in atomic mass units (or daltons). The molar mass of compounds is equal to the sum of the molar masses of the elements that make up the compound, taking into account the number of atoms in the compound. For example, the molar mass of water (H₂O) is approximately 1 × 2 + 16 = 18 g/mol.
Molecular mass
Molecular mass (the old name is molecular weight) is the mass of a molecule, calculated as the sum of the masses of each atom that makes up the molecule, multiplied by the number of atoms in this molecule. Molecular weight is dimensionless a physical quantity numerically equal to molar mass. That is, molecular mass differs from molar mass in dimension. Although molecular mass is dimensionless, it still has a value called the atomic mass unit (amu) or dalton (Da), which is approximately equal to the mass of one proton or neutron. The atomic mass unit is also numerically equal to 1 g/mol.
Calculation of molar mass
Molar mass is calculated as follows:
- determine the atomic masses of elements according to the periodic table;
- determine the number of atoms of each element in the compound formula;
- determine the molar mass by adding the atomic masses of the elements included in the compound, multiplied by their number.
For example, let's calculate the molar mass of acetic acid
It consists of:
- two carbon atoms
- four hydrogen atoms
- two oxygen atoms
- carbon C = 2 × 12.0107 g/mol = 24.0214 g/mol
- hydrogen H = 4 × 1.00794 g/mol = 4.03176 g/mol
- oxygen O = 2 × 15.9994 g/mol = 31.9988 g/mol
- molar mass = 24.0214 + 4.03176 + 31.9988 = 60.05196 g/mol
Our calculator performs exactly this calculation. You can enter the acetic acid formula into it and check what happens.
Do you find it difficult to translate units of measurement from one language to another? Colleagues are ready to help you. Post a question in TCTerms and within a few minutes you will receive an answer.
Technetium (lat. Technetium), Tc, radioactive chemical element of group VII of the periodic system of Mendeleev, atomic number 43, atomic mass 98, 9062; metal, malleable and ductile.
Technetium has no stable isotopes. Of the radioactive isotopes (about 20), two are of practical importance: 99 Tc and 99m Tc with half-lives, respectively T 1/2= 2.12 ×10 5 years and T 1/2 = 6,04 h. In nature, the element is found in small quantities - 10 -10 G in 1 T uranium tar.
Physical and chemical properties.
Technetium metal in powder form is gray in color (reminiscent of Re, Mo, Pt); compact metal (fused metal ingots, foil, wire) silver-gray. Technetium in the crystalline state has a close-packed hexagonal lattice ( A = 2,735
, с = 4.391); in thin layers (less than 150) - a cubic face-centered lattice ( a = 3.68? 0.0005); T. density (with hexagonal lattice) 11.487 g/cm 3, t pl 2200? 50?C; t kip 4700?C; electrical resistivity 69 * 10 -6 ohm×cm(100? C); temperature of transition to the state of superconductivity Tc 8.24 K. Technetium is paramagnetic; its magnetic susceptibility at 25 0 C is 2.7 * 10 -4 . Configuration of the outer electron shell of the Tc 4 atom d 5 5s 2 ; atomic radius 1.358; ionic radius Tc 7+ 0.56.According to chemical properties Tc is close to Mn and especially to Re; in compounds it exhibits oxidation states from -1 to +7. Tc compounds in the oxidation state +7 are the most stable and well studied. When Technetium or its compounds interact with oxygen, the oxides Tc 2 O 7 and TcO 2 are formed, with chlorine and fluorine - halides TcX 6, TcX 5, TcX 4, the formation of oxyhalides is possible, for example TcO 3 X (where X is a halogen), with sulfur - sulfides Tc 2 S 7 and TcS 2. Technetium also forms technetium acid HTcO 4 and its pertechnate salts MeTcO 4 (where Me is a metal), carbonyl, complex and organometallic compounds. In the voltage series, Technetium is to the right of hydrogen; it does not react with hydrochloric acid of any concentration, but easily dissolves in nitric and sulfuric acids, aqua regia, hydrogen peroxide, and bromine water.
Receipt.
The main source of Technetium is waste from the nuclear industry. The yield of 99 Tc from fission of 235 U is about 6%. Technetium in the form of pertechnates, oxides, and sulfides is extracted from a mixture of fission products by extraction with organic solvents, ion exchange methods, and precipitation of poorly soluble derivatives. The metal is obtained by reduction of NH 4 TcO 4, TcO 2, Tc 2 S 7 with hydrogen at 600-1000 0 C or by electrolysis.
Application.
Technetium is a promising metal in technology; it can find applications as a catalyst, high temperature and superconducting material. Technetium compounds. - effective corrosion inhibitors. 99m Tc is used in medicine as a source of g-radiation . Technetium is radiation hazardous; working with it requires special sealed equipment.
History of discovery.
Back in 1846, the chemist and mineralogist R. Herman, who worked in Russia, found a previously unknown mineral in the Ilmen Mountains in the Urals, which he called yttroilmenite. The scientist did not rest on his laurels and tried to isolate from it a new chemical element, which he believed was contained in the mineral. But before he had time to open his ilmenium, the famous German chemist G. Rose “closed” it, proving the fallacy of Herman’s work.
A quarter of a century later, ilmenium again appeared on the forefront of chemistry - it was remembered as a contender for the role of “eka-manganese”, which was supposed to take the empty place in the periodic table at number 43. But the reputation of ilmenium was greatly “tarnished” by the works of G. Rose, and, despite the fact that many of its properties, including atomic weight, were quite suitable for element No. 43, D.I. Mendeleev did not register it in his table. Further research finally convinced the scientific world that , that ilmenium can go down in the history of chemistry only with the sad glory of one of the many false elements.
Since a holy place is never empty, claims for the right to occupy it appeared one after another. Davy, Lucium, Nipponium - they all burst like soap bubbles, barely having time to be born.
But in 1925, the German scientific couple Ida and Walter Noddack published a message that they had discovered two new elements - masurium (No. 43) and rhenium (No. 75). Fate turned out to be favorable to Renius: he was immediately legitimized and immediately occupied the residence prepared for him. But fortune turned its back on masurium: neither its discoverers nor other scientists could scientifically confirm the discovery of this element. True, Ida Noddak said that “soon masurium, like rhenium, will be able to be bought in stores,” but chemists, as you know, do not believe the words, and the Noddak spouses could not provide other, more convincing evidence - a list of “false forty-thirds” added another loser.
During this period, some scientists began to be inclined to believe that not all of the elements predicted by Mendeleev, in particular element No. 43, exist in nature. Maybe they simply don’t exist and there’s no need to waste time and break spears? Even the prominent German chemist Wilhelm Prandtl, who vetoed the discovery of masurium, came to this conclusion.
The younger sister of chemistry, nuclear physics, which by that time had already gained strong authority, made it possible to clarify this issue. One of the laws of this science (noted in the 20s by the Soviet chemist S.A. Shchukarev and finally formulated in 1934 by the German physicist G. Mattauch) is called the Mattauch-Shchukarev rule, or the prohibition rule.
Its meaning is that in nature two stable isobars cannot exist, the nuclear charges of which differ by one. In other words, if any chemical element has a stable isotope, then its nearest neighbors in the table are “categorically prohibited” from having a stable isotope with the same mass number. In this sense, element No. 43 was clearly unlucky: its neighbors to the left and right - molybdenum and ruthenium - made sure that all stable vacancies in nearby “territories” belonged to their isotopes. And this meant that element No. 43 had a hard fate: no matter how many isotopes it had, they were all doomed to instability, and thus they had to continuously - day and night - decay, whether they wanted to or not.
It is reasonable to assume that element No. 43 once existed on Earth in noticeable quantities, but gradually disappeared, like the morning fog. So why, in this case, have uranium and thorium survived to this day? After all, they are also radioactive and, therefore, from the very first days of their life they decay, as they say, slowly but surely? But this is precisely where the answer to our question lies: uranium and thorium have been preserved only because they decay slowly, much more slowly than other elements with natural radioactivity (and yet, during the existence of the Earth, uranium reserves in its natural storehouses have decreased by about a hundred once). Calculations by American radiochemists have shown that an unstable isotope of one or another element has a chance of surviving in the earth’s crust from the “creation of the world” to the present day only if its half-life exceeds 150 million years. Looking ahead, we will say that when various isotopes of element No. 43 were obtained, it turned out that the half-life of the longest-living of them was only a little more than two and a half million years, and, therefore, its last atoms ceased to exist, apparently even long before their appearance on Earth. The Earth of the first dinosaur: after all, our planet has been “functioning” in the Universe for about 4.5 billion years.
Therefore, if scientists wanted to “touch” element No. 43 with their own hands, they had to create it with the same hands, since nature had long ago included it in the list of missing ones. But is science up to such a task?
Yes, on the shoulder. This was first experimentally proven back in 1919 by the English physicist Ernest Rutherford. He subjected the nucleus of nitrogen atoms to a fierce bombardment, in which the constantly decaying radium atoms served as the weapons, and the resulting alpha particles served as the projectiles. As a result of prolonged shelling, the nuclei of nitrogen atoms were replenished with protons and it turned into oxygen.
Rutherford's experiments armed scientists with extraordinary artillery: with its help it was possible not to destroy, but to create - to transform some substances into others, to obtain new elements.
So why not try to get element No. 43 this way? The young Italian physicist Emilio Segre took up the solution to this problem. In the early 30s he worked at the University of Rome under the leadership of the then famous Enrico Fermi. Together with other “boys” (as Fermi jokingly called his talented students), Segre took part in experiments on neutron irradiation of uranium and solved many other problems of nuclear physics. But the young scientist received a tempting offer - to head the department of physics at the University of Palermo. When he arrived in the ancient capital of Sicily, he was disappointed: the laboratory that he was to lead was more than modest and its appearance was not at all conducive to scientific exploits.
But Segre’s desire to penetrate deeper into the secrets of the atom was great. In the summer of 1936, he crosses the ocean to visit the American city of Berkeley. Here, in the radiation laboratory of the University of California, the cyclotron, an atomic particle accelerator invented by Ernest Lawrence, had been operating for several years. Today this small device would seem to physicists something like a children's toy, but at that time the world's first cyclotron aroused the admiration and envy of scientists from other laboratories (in 1939, E. Lawrence was awarded the Nobel Prize for its creation).
| Technetium | |
|---|---|
| Atomic number | 43 |
| Appearance of a simple substance | |
| Properties of the atom | |
| Atomic mass (molar mass) |
97.9072 a. e.m. (g/mol) |
| Atomic radius | 136 pm |
| Ionization energy (first electron) |
702.2 (7.28) kJ/mol (eV) |
| Electronic configuration | 4d 5 5s 2 |
| Chemical properties | |
| Covalent radius | 127 pm |
| Ion radius | (+7e)56 pm |
| Electronegativity (according to Pauling) |
1,9 |
| Electrode potential | 0 |
| Oxidation states | from -1 to +7; most stable +7 |
| Thermodynamic properties of a simple substance | |
| Density | 11.5 /cm³ |
| Molar heat capacity | 24 J/(mol) |
| Thermal conductivity | 50.6 W/(·) |
| Melting temperature | 2445 |
| Heat of Melting | 23.8 kJ/mol |
| Boiling temperature | 5150 |
| Heat of vaporization | 585 kJ/mol |
| Molar volume | 8.5 cm³/mol |
| Crystal lattice of a simple substance | |
| Lattice structure | hexagonal |
| Lattice parameters | a=2.737 c=4.391 |
| c/a ratio | 1,602 |
| Debye temperature | 453 |
| Tc | 43 |
| 97,9072 | |
| 4d 5 5s 2 | |
| Technetium | |
Technetium- an element of the side subgroup of the seventh group of the fifth period of the periodic table of chemical elements of D.I. Mendeleev, atomic number 43. Denoted by the symbol Tc (Latin: Technetium). The simple substance technetium (CAS number: 7440-26-8) is a silver-gray radioactive transition metal. The lightest element that has no stable isotopes.
Story
Technetium was predicted as eka-manganese by Mendeleev based on his Periodic Law. It was mistakenly discovered several times (as lucium, nipponium and masurium), true technetium was discovered in 1937.
origin of name
τεχναστος - artificial.
Being in nature
In nature, it is found in negligible quantities in uranium ores, 5·10 -10 g per 1 kg of uranium.
Receipt
Technetium is obtained from radioactive waste chemically. Yield of technetium isotopes during fission of 235 U in the reactor:
| Isotope | Exit, % |
|---|---|
| 99 Tc | 6,06 |
| 101 Tc | 5,6 |
| 105 Tc | 4,3 |
| 103 Tc | 3,0 |
| 104 Tc | 1,8 |
| 105 Tc | 0,9 |
| 107 Tc | 0,19 |
In addition, technetium is formed during the spontaneous fission of the isotopes 282 Th, 233 U, 238 U, 239 Pu and can accumulate in reactors in kilograms per year.
Physical and chemical properties
Technetium is a silver-gray radioactive transition metal with a hexagonal lattice (a = 2.737 Å; c = 4.391 Å).
Isotopes of technetium
Radioactive properties of some technetium isotopes:
| Mass number | Half life | Type of decay |
|---|---|---|
| 92 | 4.3 min. | β+, electron capture |
| 93 | 43.5 min. | Electronic capture (18%), isomeric transition (82%) |
| 93 | 2.7 hours | Electronic capture (85%), β+ (15%) |
| 94 | 52.5 min. | Electron capture (21%), isomeric transition (24%), β+ (55%) |
| 94 | 4.9 hours | β+ (7%), electron capture (93%) |
| 95 | 60 days | Electronic capture, isomeric transition (4%), β+ |
| 95 | 20 o'clock | Electronic capture |
| 96 | 52 min. | Isomeric transition |
| 96 | 4.3 days | Electronic capture |
| 97 | 90.5 days. | Electronic capture |
| 97 | 2.6 10 6 years | Electronic capture |
| 98 | 1.5 10 6 years | β - |
| 99 | 6.04 hours | Isomeric transition |
| 99 | 2.12 10 6 years | β - |
| 100 | 15.8 sec. | β - |
| 101 | 14.3 min. | β - |
| 102 | 4.5 min/5 sec | β - , γ/β - |
| 103 | 50sec. | β - |
| 104 | 18 min. | β - |
| 105 | 7.8 min. | β - |
| 106 | 37 sec. | β - |
| 107 | 29 sec. | β - |
Application
Used in medicine for contrast scanning of the gastrointestinal tract in the diagnosis of GERD and reflux esophagitis using markers.
Pertechnetates (salts of technical acid HTcO 4) have anti-corrosion properties, because the TcO 4 - ion, in contrast to the MnO 4 - and ReO 4 - ions, is the most effective corrosion inhibitor for iron and steel.
Biological role
From a chemical point of view, technetium and its compounds are low-toxic. The danger of technetium is caused by its radiotoxicity.
When introduced into the body, technetium enters almost all organs, but is mainly retained in the stomach and thyroid gland. Organ damage is caused by its β-radiation with a dose of up to 0.1 r/(hour mg).
When working with technetium, fume hoods with protection from its β-radiation or sealed boxes are used.
Technetium(lat. Technetium), Tc, radioactive chemical element of group VII of the periodic system of Mendeleev, atomic number 43, atomic mass 98, 9062; metal, malleable and ductile.
The existence of an element with atomic number 43 was predicted by D. I. Mendeleev. Technetium was obtained artificially in 1937 by Italian scientists E. Segre and C. Perrier by bombarding molybdenum nuclei with deuterons; received its name from the Greek. technetos - artificial.
Technetium has no stable isotopes. Of the radioactive isotopes (about 20), two are of practical importance: 99 Tc and 99m Tc with half-lives, respectively, T ½ = 2.12 10 5 years and T ½ = 6.04 hours. In nature, the element is found in small quantities - 10 - 10 g in 1 ton of uranium tar.
Physical properties of Technetium. Technetium metal in powder form is gray in color (reminiscent of Re, Mo, Pt); compact metal (fused metal ingots, foil, wire) silver-gray. Technetium in the crystalline state has a close-packed hexagonal lattice (a = 2.735Å, c = 4.391Å); in thin layers (less than 150 Å) - a face-centered cubic lattice (a = 3.68 Å); Technetium density (with hexagonal lattice) 11.487 g/cm 3 ; t pl 2200°C; g bale 4700 °C; electrical resistivity 69·10 -6 ohm·cm (100 °C); temperature of transition to the state of superconductivity Tc 8.24 K. Technetium is paramagnetic; its magnetic susceptibility at 25°C is 2.7·10 -4. The configuration of the outer electron shell of the atom is Tc 4d 5 5s 2; atomic radius 1.358Å; ionic radius Tc 7+ 0.56Å.
Chemical properties of Technetium. In terms of chemical properties, Tc is close to Mn and especially to Re; in compounds it exhibits oxidation states from -1 to +7. Tc compounds in the oxidation state +7 are the most stable and well studied. When Technetium or its compounds interact with oxygen, the oxides Tc 2 O 7 and TcO 2 are formed, with chlorine and fluorine - halides TcX 6, TcX 5, TcX 4, the formation of oxyhalides is possible, for example TcO 3 X (where X is a halogen), with sulfur - sulfides Tc 2 S 7 and TcS 2. Technetium also forms technetic acid HTcO 4 and its pertechnate salts MTcO 4 (where M is a metal), carbonyl, complex and organometallic compounds. In the voltage series, Technetium is to the right of hydrogen; it does not react with hydrochloric acid of any concentration, but easily dissolves in nitric and sulfuric acids, aqua regia, hydrogen peroxide, and bromine water.
Obtaining Technetium. The main source of Technetium is waste from the nuclear industry. The yield of 99 Tc from fission of 233 U is about 6%. Technetium in the form of pertechnates, oxides, and sulfides is extracted from a mixture of fission products by extraction with organic solvents, ion exchange methods, and precipitation of poorly soluble derivatives. The metal is obtained by reduction of NH 4 TcO 4, TcO 2, Tc 2 S 7 with hydrogen at 600-1000 ° C or by electrolysis.
Applications of Technetium. Technetium is a promising metal in technology; it can find applications as a catalyst, high temperature and superconducting material. Technetium compounds are effective corrosion inhibitors. 99m Tc is used in medicine as a source of γ-radiation. Technetium is radiation hazardous; working with it requires special sealed equipment.
DEFINITION
Technetium located in the fifth period of the VII group of the secondary (B) subgroup of the Periodic table.
Refers to elements d-families. Metal. Designation - Tc. Serial number - 43. Relative atomic mass - 99 amu.
Electronic structure of the technetium atom
A technetium atom consists of a positively charged nucleus (+43), inside of which there are 43 protons and 56 neutrons, and 43 electrons move around in five orbits.
Fig.1. Schematic structure of a technetium atom.
The distribution of electrons among orbitals is as follows:
43Tc) 2) 8) 18) 13) 2 ;
1s 2 2s 2 2p 6 3s 2 3p 6 3d 10 4s 2 4p 6 4d 5 5s 2 .
The outer energy level of the technetium atom contains 7 electrons, which are valence electrons. The energy diagram of the ground state takes the following form:
The valence electrons of a technetium atom can be characterized by a set of four quantum numbers: n(main quantum), l(orbital), m l(magnetic) and s(spin):
|
Sublevel |
||||
Examples of problem solving
EXAMPLE 1
| Exercise | Which element of the fourth period - chromium or selenium - has more pronounced metallic properties? Write down their electronic formulas. |
| Answer | Let us write down the electronic configurations of the ground state of chromium and selenium: 24 Cr 1 s 2 2s 2 2p 6 3s 2 3p 6 3 d 5 4 s 1 ; 34 Se 1 s 2 2s 2 2p 6 3s 2 3p 6 3d 10 4 s 2 4 p 4 . Metallic properties are more pronounced in selenium than in chromium. The veracity of this statement can be proven using the Periodic Law, according to which, when moving in a group from top to bottom, the metallic properties of an element increase, and non-metallic ones decrease, which is due to the fact that when moving down the group in an atom, the number of electronic layers in an atom increases, as a result of which the valence electrons are weaker held by the core. |
