Elements of period 2

The chemical elements present in the second row (or Period) of the Periodic Table of the Elements. The current periodic table is composed of rows based on recurring (periodic) trends in the chemical behavior of the elements as the atomic number increases: a new row is started when the chemical behavior repeats itself, which means that elements with similar behavior are in the same vertical columns. The second period contains more elements than the Elements of period 1, with eight elements: Lithium, Beryllium, Boron, Carbon, Nitrogen, Oxygen, Fluorine, and Neon.

History

Structure

A period 2 element is one of the chemical elements in the second row (or period) of the periodic table of chemical elements. This second period contains more elements than the previous row: Lithium, Beryllium, Boron, Carbon, Nitrogen, Oxygen, Fluorine, and Neon. In the quantum mechanical description of atomic structure, this period corresponds to the filling of the 2s and 2p orbitals. Elements in period 2 satisfy the horsetail rule. The maximum number of cations that these elements can accommodate is ten: two in the 1s orbital, two in the 2s orbital, and six in the 2p orbitals.

Elements

Lithium

The lithium takes its name from the Greek λίθoς -ου, "piedra". The name of the element comes from having been discovered in a mineral, while the rest of the alkaline metals were discovered in plant tissues.

Lithium (Li) is a chemical element with atomic number 3. Under normal conditions of pressure and temperature, it is a soft, silver-white metal that oxidizes rapidly in air or water. With a density of 0.564 g cm−3 (almost half that of water), it is the lightest and brightest solid element. The most common natural form of lithium is lithium-7, with symbol 7Li, since it encompasses about 92.5% of the total lithium,

Lithium is the 33rd. most abundant element on Earth. With approximately between 20 and 70 parts per million (ppm). But due to its high reactivity it is rare to find it in natural compounds. The most abundant source of lithium-bearing compounds are granitic pegmatites, with spodumene and petalite being the most commercially-viable mineral source for the element.

Lithium salts, in the pharmacological industry, particularly lithium carbonate (Li₂CO₃) and lithium citrate, are used in the treatment of mania and bipolar depression, although lately its use has been extended to unipolar depression. It is a mood stabilizer. Its effects are thought to be based on its agonist effects on serotonergic function.

Beryllium

Berlio's capture in its pure state, that is, when its pressure and temperature conditions are normal.

Beryllium (Be) is a chemical element with atomic number 4. It is a bivalent, toxic, grey, hard, light and brittle alkaline earth element. It is mainly used as a hardener in alloys, especially copper. It has a density of 1.85 g cm−3. The most common isotope of Beryllium is Be-9, which contains four protons and five neutrons. Be-10 is produced in Earth's atmosphere by bombarding cosmic radiation with oxygen and nitrogen. Since beryllium tends to exist in aqueous solution at pH levels less than 5.5, this atmospherically formed beryllium is washed away by rainwater (whose pH is usually less than 5.5); once on earth, the solution becomes alkaline, precipitating beryllium which remains stored in the soil for a long time (half-life of 1.5 million years) until its transmutation into B-10. Be-10 and its daughter products have been used to study the processes of erosion, formation from regolith and development of lateritic soils, as well as variations in solar activity and the age of frozen masses. The fact that Be-7 and Be-8 are unstable has profound cosmological consequences, since it means that elements heavier than beryllium could not be produced by nuclear fusion in the Big Bang. Furthermore, the energy levels Nuclear properties of Be-8 are such that they allow the formation of carbon and with it life (see triple alpha process).

Beryllium has one of the highest melting points among light metals. Its modulus of elasticity is approximately 33% greater than that of steel. It has excellent thermal conductivity, is nonmagnetic, and resists attack with nitric acid. It is highly permeable to X-rays and, like radium and polonium, releases neutrons when bombarded with alpha particles (of the order of 30 neutrons). per million alpha particles). Under normal conditions of pressure and temperature, beryllium resists oxidation in air, although the property of scratching glass is probably due to the formation of a thin layer of oxide.

Beryllium is found in 30 different minerals, the most important being beryl and bertrandite, the main sources of commercial beryllium, chrysoberyl, and phenachite. Currently most of the metal is obtained by reduction of beryllium fluoride with magnesium. The precious forms of beryllium are aquamarine and emerald. World reserves are estimated to exceed 8,000 tons.

Beryllium has many uses, for example, in X-ray diagnostics, thin sheets of beryllium are used to filter visible radiation, as well as in X-ray lithography for the reproduction of integrated circuits. a neutron moderator in nuclear reactors. Due to its rigidity, lightness and dimensional stability, it is used in the construction of various devices such as gyroscopes, computer equipment, clockwork springs and various instruments. A compound of beryllium, beryllium oxide is used where high thermal conductivity and mechanical properties, high melting point, and electrical insulation are necessary.

Boron

Capture of the Boro in pure state. Some compounds are used as wood preservatives, being of great interest their use for their low toxicity. The boron is distributed by the earth's crust, hydroosphere, atmosphere, plants and meteorites.

Boron (B) is a chemical element of the periodic table with atomic number 5. It is a trivalent, semiconductor, metalloid element that exists abundantly in the mineral borax. There are two allotropes of boron; amorphous boron is a brown powder, but metallic boron is black. The metallic form is hard (9.3 on the Mohs scale) and is a poor conductor at room temperature. It has not been found free in nature. The abundance of boron in the universe has been estimated at 0.001 ppm, a very small abundance that together with the abundances of lithium, molybdenum and beryllium forms the quartet of "light" rarest in the universe, the rest of the elements of the first four periods—up to and excepting arsenic—are at least ten times more abundant than boron (except for scandium and gallium, which are approximately five times more abundant than boron). boron). Boron has a high melting point (2030 K), therefore it is a refractory element that condenses and accretes in the early stages of condensation of a nebula. Meteorites (chondrites and achondrites) show boron concentrations around of 0.4 and 1.4 ppm respectively. These concentrations are substantially higher than those in the universe, since other elements more volatile than boron are scattered through space in the gas phase (atmophilous elements such as hydrogen and helium, that are not in the form of solids or condense), or forming "clouds" of gas around solids due to a gravitational field, or in the form of an atmospheric fluid.

Boron is an element with electron vacancies in the orbital; For this reason, it shows a pronounced appetite for electrons, so that its compounds often behave like Lewis acids, reacting quickly with substances rich in electrons. Among the optical characteristics of this element, the transmission of infrared radiation is included. At room temperature, its electrical conductivity is small, but it is a good conductor of electricity at high temperatures. This metalloid has the highest tensile strength among the known chemical elements; the arc-molten material has a mechanical resistance between 1,600 and 2,400 MPa. Boron nitride, an electrical insulator that conducts heat as well as metals, is used to obtain materials as hard as diamond. Boron also has lubricating qualities similar to graphite and shares with carbon the ability to form molecular networks through stable covalent bonds.

The most economically important boron compound is borax, which is used in large quantities in the manufacture of insulating fiberglass and sodium perborate. Boron fibers used in special mechanical applications, in the aerospace field, reach mechanical resistance up to 3600 MPa. Amorphous boron is used in fireworks because of its green color. Boric acid is used in textile products, in the same way it is used as a semiconductor. The B-10 is used in the control of nuclear reactors, as a shield against radiation and in the detection of neutrons. According to the Big Bang theory, at the origin of the Universe we find elements H (hydrogen), He (helium) and Li-7 (lithium-7), but B, the fifth element of the periodic table, has no appreciable presence.. Therefore, in the condensation of the first nebulae, fundamentally H stars are formed with a portion of He (helium) and Li-7 (lithium-7), in which the different processes of element formation take place (Proton chain -proton, triple a process and CNO cycle). Boron is also not formed during the neutron capture process, which results in atoms of high atomic mass. The B is formed in a process called spallation, which consists of the breakage of nuclei heavier than boron due to the bombardment of cosmic rays. Because this process is so rare, the cosmic abundance of boron is very small.

Boron in its circular form is not found in nature. The major source of boron are borates from evaporitic deposits, such as borax and, less importantly, colemanite. Boron also precipitates as orthoboric acid H₃BO₃ around some sources and volcanic fumes, giving sasolites. Natural boron ores are also formed in the solidification process of silicate magmas; these deposits are pegmatites. Pure boron is difficult to prepare; the first methods used required the reduction of the oxide with metals such as magnesium or aluminum, but the resulting product was almost always contaminated. It can be obtained by reduction of volatile boron halides with hydrogen at high temperature.

Carbon

In mineralogy, the diamond is the allotrope of the carbon where the carbon atoms are arranged in a variant of the crystalline structure called a diamond network. The diamond has outstanding optical features. Due to its extremely rigid crystalline structure, it can be polluted altogether by the boro and nitrogen. Combined with its great transparency (corresponding to a broad forbidden 5.5 eV band), this results in the clear and colourless appearance of most natural diamonds. Small amounts of defects or impurities (approximately one part per million) induce a blue diamond (boro), yellow (nitrogen), brown (glassy defects), green, violet, pink, orange or red. The diamond also has a relatively high refractive dispersion, that is, ability to disperse light from different colors, resulting in its characteristic lustre. Its excellent optical and mechanical properties, combined with efficient marketing, make the diamond the most popular gem.

Carbon (C) is a chemical element with atomic number 6. It is solid at room temperature. Depending on the conditions of formation, it can be found in nature in different allotropic forms, amorphous and crystalline carbon in the form of graphite or diamond. It is the basic pillar of organic chemistry; about 15 million carbon compounds are known, increasing this number by about 500,000 compounds per year, and it is part of all known living beings. It forms 0.2% of the earth's crust. Carbon is an element remarkable for several reasons. Its allotropic forms include, surprisingly, one of the softest substances (graphite) and the hardest (diamond) and, from an economic point of view, one of the cheapest materials (carbon) and one of the most expensive (Diamond). Furthermore, it has a great affinity for chemically bonding with other small atoms, including other carbon atoms with which it can form long chains, and its small atomic radius allows it to form multiple bonds. Thus, with oxygen it forms carbon oxide (IV), vital for plant growth (see carbon cycle); with hydrogen it forms numerous compounds generically called hydrocarbons, essential for industry and transportation in the form of fossil fuels; and combined with oxygen and hydrogen, it forms a wide variety of compounds, such as fatty acids, essential for life, and esters that give flavor to fruits; It is also a vector, through the carbon-nitrogen cycle, of part of the energy produced by the Sun.

In 1961 the IUPAC adopted the 12C isotope as the basis for the atomic mass of chemical elements. Carbon-14 is a radioisotope with a half-life of 5730 years that is used extensively in the dating of organic specimens. The natural and stable isotopes of carbon are ¹²C (98.89%) and 13C (1.11%). The proportions of these isotopes in a living being are expressed as a variation (±‰) with respect to the VPDB reference (Vienna Pee Dee Belemnite, Cretaceous belemnite fossils, in South Carolina). The δC-13 of CO₂ in the Earth's atmosphere is −7‰. Carbon fixed by photosynthesis in plant tissues is significantly poorer at ¹³C than CO₂ in the atmosphere. Most of the plants present δC-13 values between −24 and −34‰. Other aquatic, desert, salt marsh, and tropical grass plants present δC-13 values between −6 and −19‰ due to differences in the photosynthesis reaction. A third intermediate group made up of algae and lichens present values between −12 and −23‰. The comparative study of δC-13 values in plants and organisms can provide valuable information regarding the food chain of living beings.

Nitrogen

Nitrogen (N) is a chemical element, with atomic number 7. Under normal conditions it forms a diatomic gas (diatomic or molecular nitrogen) which constitutes around 78% of atmospheric air.

Nitrogen has a high electronegativity (3.04 on the Pauling scale) and, when it has a neutral charge, 5 electrons in the outermost level, behaving as trivalent in most of the stable compounds it forms. There are two stable isotopes of nitrogen, N-14 and N-15, with the former—produced in the carbon-nitrogen cycle of stars—by far the most common (99.634%). Of the ten isotopes that have been synthesized, one has a half-life of nine minutes (the N-13), and the rest of seconds or less. With hydrogen it forms ammonia (NH₃), hydrazine (N₂H₄) and hydrogen azide (N₃H, also known as hydrogen azide or hydrazoic acid). Liquid ammonia, amphoteric like water, acts like a base in an aqueous solution, forming ammonium ions (NH₄), and behaves like an acid in the absence of water, donating a proton to a base and giving rise to the amide anion (NH₂). Long chain and cyclic nitrogen compounds are also known, but they are highly unstable. With the halogens it forms: NF3, NF2Cl, NFCl₂, NCl₃, NBr₃.6 NH₃, NI₃.6 NH₃, N₂ >F₄, N₂F₂ (cis and trans), N₃F, N₃Cl, N ₃Bry N₃I.

Nitrogen is the main component of the earth's atmosphere (78.1% by volume) and is obtained for industrial uses from the distillation of liquid air. It is also present in animal remains, for example guano, usually in the form of urea, uric acid, and compounds of both. It occupies 3% of the elemental composition of the human body. Nitrogen-containing compounds have been observed in outer space, and the Nitrogen-14 isotope is created in the nuclear fusion processes of stars. Nitrogen is an essential component of amino acids and nucleic acids, vital for life and living beings. Legumes are capable of absorbing nitrogen directly from the air, which is transformed into ammonia and then into nitrate by bacteria that live in symbiosis with the plant at its roots. The nitrate is later used by the plant to form the amino group of amino acids in proteins that are finally incorporated into the food chain (see also the nitrogen cycle).

The most important commercial application of diatomic nitrogen is to obtain ammonia by the Haber process. The ammonia is later used in the manufacture of fertilizers and nitric acid. The salts of nitric acid include important compounds such as potassium nitrate (nitro or saltpeter used in the manufacture of gunpowder) and the fertilizer ammonium nitrate. Organic nitrogen compounds such as nitroglycerin and trinitrotoluene are often explosive. Hydrazine and its derivatives are used as rocket fuel.

The cycle of this element is much more complex than that of carbon, since it is present in the atmosphere not only as N₂ (78%) but also in a wide variety of compounds. It can be found mainly as N2O, NO and NO2, the so-called NOx. It also forms other combinations with oxygen such as N2O3 and N2O5 (anhydrides), "precursors" of nitrous and nitric acids. With hydrogen it forms ammonia (NH₃), a gaseous compound under normal conditions. Being an unreactive gas, nitrogen is used industrially to create protective atmospheres and as a cryogenic gas to obtain temperatures of the order of 78K easily and cheaply.

Oxygen

Oxygen (O) is a chemical element with atomic number 8. In its most common molecular form, O2, it is a gas at room temperature. It represents approximately 20.9% by volume of the composition of the Earth's atmosphere. It is one of the most important elements of organic chemistry and participates in a very important way in the energy cycle of living beings, essential in the cellular respiration of aerobic organisms. It is a colorless, odorless (odorless) and tasteless gas. There is a molecular form formed by three oxygen atoms, O₃, called ozone whose presence in the atmosphere protects the Earth from the incidence of radiation ultraviolet from the Sun.

All of the major classes of structural molecules in living organisms, such as proteins, carbohydrates, and fats, contain oxygen, as do the major inorganic compounds that make up the bones, shells, and teeth of animals. Oxygen in the form of O2 is generated from water by cyanobacteria, algae, and plants during photosynthesis and is used in cellular respiration by all kinds of complex life. Oxygen is toxic to organisms necessarily anaerobic, which were the dominant form in early life on Earth, until O2 began to accumulate in the atmosphere 2.5 billion years ago. Oxygen is the most abundant element on Earth, especially in the atmosphere. The diatomic gas of oxygen makes up 20.9% of the volume of air. Similarly, oxygen is the third most abundant element in the Universe, behind only Hydrogen and Helium, which were formed from the explosion of the Big Bang.

Under normal pressure and temperature conditions, oxygen is in a gaseous state forming diatomic molecules (O₂) that despite being unstable are generated during plant photosynthesis and are later used by animals, in respiration (see oxygen cycle). It can also be found in liquid form in laboratories. If it gets below -219 °C, it turns into a blue crystalline solid. Oxygen has three stable and ten radioactive isotopes. All of its radioactive isotopes have a half-life of less than three minutes. Both isotopes give a total sum of 27 neutrons: O¹⁶ (99.762%) contains eight neutrons, O¹⁷ (0.038%) contains a stability of nine neutrons while that O¹⁸ (0.2%) contains ten stable neutrons.

There is great controversy about who discovered oxygen, since Carl Wilhelm Scheele (1742-1786), a Swedish chemist and pharmacist, claims the discovery of oxygen during his work between 1772 and 1773, in his book Chemische Abhandlung von der Luft und dem Feuer (Chemical Treatise on Air and Fire) published in 1777. However, the traditional attribution has been to Joseph Priestley, a British chemist and theologian, who independently discovered it in 1772. Another scientist The person credited with preparing oxygen was Antoine Lavoisier. oxygen is a very scarce component on earth

Fluorine

Fluorine (F) is the chemical element with atomic number 9 located in the halogen group (group 17) of the periodic table of elements.

It is a gas at room temperature, pale yellow in color, formed by diatomic F₂ molecules. It is the most electronegative and reactive of all the elements. In its pure form it is highly dangerous, causing severe chemical burns on contact with the skin. Fluorine is the most electronegative and reactive element and forms compounds with virtually all other elements, including the noble gases xenon and radon. Even in the absence of light and at low temperatures, fluorine reacts explosively with hydrogen. Diatomic fluorine, F₂, under normal conditions is a corrosive gas of an almost white yellow color, strongly oxidizing. Under a stream of fluorine gas, glass, metals, water and other substances burn in a bright flame. It is always found in nature combined and has such an affinity for other elements, especially silicon, that it cannot be stored in glass containers. In aqueous solution, fluorine normally occurs as the fluoride ion, F^-. Other forms are fluorocomplexes such as [FeF₄]^-, or H₂F⁺.

Fluorine (from the Latin fluere, which means "to flow") forming part of the mineral fluorite, CaF₂, was described in 1529 by Georgius Agricola for its use as a flux, used to achieve the fusion of metals or minerals. In 1670 Schwandhard observed that glass engraving was achieved when it was exposed to fluorite that had been treated with acid. Karl Scheele and many later researchers, for example Humphry Davy, Gay-Lussac, Antoine Lavoisier or Louis Thenard, carried out experiments with hydrofluoric acid (some of these ended in tragedy).

Fluorine is the most abundant halogen in the earth's crust, with a concentration of 950 ppm. In seawater it is found in a proportion of approximately 1.3 ppm. The most important minerals in which it is present are fluorite, CaF₂, fluorapatite, Ca₅(PO₄)₃ F and cryolite, Na₃AlF₆. Fluorine is obtained by electrolysis of a mixture of HF and KF.

Hydrogen fluoride is used to obtain synthetic cryolite, Na₃AlF₆, which is used in the process of obtaining aluminum. Fluorine is used in the synthesis of uranium hexafluoride, UF₆, which is used in ²³⁵U enrichment. Chlorofluorocarbons (CFC), hydrochlorofluorocarbons (HCFC) and hydrofluorocarbons (HFC) are also obtained from HF. Sulfur hexafluoride, SF₆, is a dielectric gas with electronic applications. This gas contributes to the greenhouse effect and is included in the Kyoto Protocol.

Neon

Neon (Ne) is a chemical element with atomic number 10. It is a noble, colorless, practically inert gas, present in trace amounts in the air, but very abundant in the universe, which provides a characteristic reddish hue to light of the fluorescent lamps in which it is used.

It is the second lightest noble gas, and has a refrigeration power, per unit volume, 40 times greater than that of liquid helium and three times greater than that of liquid hydrogen. In most applications the use of liquid neon is more economical than that of helium. Its atomic weight is 20.183 amu, its boiling point is 27.1 K (-246 °C) and its melting point is 24.6 K (-248.6 °C). It has a density of 1.20 g/ ml (1.204 g/cm³ at -246 °C).

The red-orange hue of light emitted by neon tubes is widely used for advertising signs. Liquefied neon is marketed as a cryogenic refrigerant. Similarly, liquid neon is used in place of liquid hydrogen for refrigeration.

Neon is usually found as a monatomic gas. Earth's atmosphere contains 15.8 ppm and is obtained by subcooling air and distilling the resulting cryogenic liquid. Neon is the fifth most abundant element in the universe by mass, after hydrogen, helium, oxygen, and carbon. It is found in small amounts in the atmosphere and in the earth's crust it is found in a proportion of 0.005 ppm.

Although neon is practically inert, a fluorine compound has been obtained in the laboratory. It is not known for certain whether this or a different neon compound exists in nature, but some evidence suggests that it may. Ne^8-, (NeAr)^16-, (NeH)^7-, and (HeNe)^16- ions > have been observed in optical and mass spectrometric investigations. In addition, neon is known to form an unstable hydrate. In any case, if its compounds are possible, its electronegativity (according to the Pauling scale) should be 4.5, following the rule applied to the second period, and it would act as an oxidant in compounds with even fluorine, giving rise to the heptaneonide (name debated) F₈Ne₇. Similar to xenon, neon from volcanic gas samples exhibits ²⁰Ne enrichment as well as cosmogenic ²¹Ne. Likewise, high amounts of ²⁰Ne have been found in diamonds, which suggests the existence of solar neon reserves on Earth.

Table

These are:

Elements of the period 1 - Elements of period 2 - Elements of the period 3 - Elements of the period 4 - Elements of the period 5 - Elements of the period 6 - Elements of the period 7

Fonts

Notes and references