[Edit this paragraph] Formation mode
There are three kinds: 1. The number of atoms that make up molecules is different, such as oxygen O2 and ozone O3. The arrangement of atoms in the lattice is different, such as diamond and graphite. 3. The arrangement of molecules in the lattice is different, such as orthogonal sulfur and monoclinic sulfur.
[Edit this paragraph] Nature and characteristics
Chemical properties: similar or slightly different physical properties: very different.
[Edit this paragraph] Example
Variation of carbon
The allotropes of (1) carbon include fullerenes such as diamond, graphite and carbon 60, and their different properties are determined by their different microstructures. Diamond is a regular tetrahedral space network with three-dimensional structure, and valence bonds are formed between carbon atoms. When cutting or melting, it is necessary to overcome the valence bond between carbon atoms. Diamond is the hardest material known in nature, and its melting point is very high. The first-class flawless diamond is crystal clear, with good refraction and dazzling. It is a favorite ornament and an indispensable and important material for cutting-edge technology. Diamonds with smaller particles and lower quality are mostly used in general industries, such as manufacturing precision parts such as instrument bearings, machining and geological drilling. Diamonds are indispensable for cutting stones, metals, ceramics, glass, etc. During grinding, sawing, drilling and polishing. Using diamond bit instead of ordinary cemented carbide bit can greatly improve drilling speed and reduce cost; A dental drill with diamonds is a convenient tool for dentists. Ophthalmic scalpel inlaid with diamonds has a sharp and smooth blade, and even with a microscope of 1000 times, no defects can be seen. It is a common weapon to remove eye cataracts. Diamond has a wide application prospect in the fields of machinery, electronics, optics, heat transfer, military, aerospace, medicine and chemistry. Graphite is a layered structure. The carbon atoms in the layer are arranged in a plane hexagon, and each carbon atom is combined with other carbon atoms through three valence bonds. The delocalized electrons in the same layer can move in the whole layer, and the carbon atoms between layers are combined by intermolecular force (van der Waals force). Graphite is a gray-black, opaque metal crystal. Natural graphite has high temperature resistance, low thermal expansion coefficient, good thermal conductivity and low friction coefficient. Graphite is widely used as electrode, crucible, brush, lubricant, pencil, etc. Graphite with layered structure can insert some atoms or groups into the layer and combine with C atoms under appropriate conditions to form graphite intercalation compounds. The properties of these intercalation compounds basically do not change the original layered structure of graphite, but the interlayer spacing increases, which is called expanded graphite. It has the winding and resilience that natural graphite does not have, and can be widely used as a new engineering material in petrochemical, fertilizer, atomic energy, electronics and other fields. (2) Carbon 60 1985, scientists at Ross University in Texas, USA, produced the third form of elemental carbon C60, which is a closed cage molecule composed of 60 carbon atoms and looks like a football. C60 is a black powder, which is easily soluble in solvents such as carbon disulfide and benzene. People named this form of elemental carbon after architect B. Fuller, which is called fullarene. This is because Fuller designed a building called a spherical dome, and some fullerenes are very similar in structure. C60 was once called soccer olefin, bucky ball, etc. It belongs to the fullerene family. The molecular formula of these substances can be expressed as Cn, and n is an integer value between 28 and 540, including C50, C70, C84, C240, etc. In these molecules, carbon atoms form two single bonds and one double bond with three other carbon atoms, which are actually spherical conjugated olefins. Fullerene molecules have attracted extensive attention because of their unique structure and properties. It is found that the surface of the cage structure of fullerene molecules is open, but the inside is empty, which may introduce other substances into the sphere, thus significantly changing the physical and chemical properties of fullerene molecules. For example, chemists try to add various metals to these hollow substances to make them superconducting. It is found that the critical temperature of the superconductor obtained by combining C60 with some alkali metals is higher than that of various superconductors studied in recent years, and scientists predict that C540 may realize room temperature superconductivity. It is also envisaged that some drugs will be put into the cavity of C60 sphere to become slow-release drugs and enter various parts of the human body. It has broad application prospects in single-molecule nano-electronic devices, and fullerenes have widely influenced various fields such as physics, chemistry, material science, life and medicine. (3) Carbon nanotubes Carbon nanotubes can be divided into single-layer and multi-layer carbon nanotubes, which are hollow carbon nanotubes formed by curling single-layer or multi-layer concentric graphite layers. The diameter of the tube is generally a few nanometers to several tens of nanometers. The spacing between graphite layers on the pipe wall is 0.34 nm, which is the same as the spacing between planar graphite layers. Carbon nanotubes, whether single-layer or multi-layer, are semi-circular at both ends, and the structure is basically similar to that of carbon sixty, making the whole carbon nanotube a closed structure, so are carbon nanotubes. Carbon nanotubes are very tiny. There are only 50,000 side by side, and a person's hair is as wide as silk, which is a fiber with a high aspect ratio. Carbon nanotubes have high strength, good toughness, light weight, large specific surface area and stable performance. They show the specific conductivity of semiconductors or good conductors with different tube wall winding structures, and have excellent field emission performance. Since the discovery of single-layer carbon nanotubes by 199 1 and the successful synthesis of macroscopic quantities, due to its unique electronic structure and physical and chemical properties, the application of carbon nanotubes in various fields has attracted wide attention from scientists all over the world and has become a research hotspot in the field of fullerenes and nanotechnology. Carbon nanotubes can be used to make high-strength carbon fiber materials and composites. For example, their strength is 100 times that of steel, and their weight is only16 of steel, so they are called "super fibers" by future scientists. In the aerospace field, using carbon nanotubes to make artificial satellite streamers can not only supply power for satellites, but also resist high temperature and non-combustion; Filling carbon nanotubes with metal, and then etching off the carbon layer, you can get nano-scale wires with very good conductivity; Using carbon nanotubes as anode and cathode materials of lithium-ion batteries can prolong the battery life and improve the battery charge and discharge performance. Carbon nanotubes are used to make excellent real-time light sources that emit light, heat and electrons, and to make flat panel displays. , making wall-mounted TV possible; In the electronics industry, the transistor size produced by carbon nanotubes is only110 of semiconductor. Replacing computer chips with carbon-based molecular electronic devices will trigger a new revolution in computers. Carbon nanotubes can store a large amount of hydrogen at low pressure. The fuel made by this method is not only safe, but also a clean energy source, which will have broad development prospects in the automobile industry. Carbon nanotubes can also be used as catalyst carriers and membrane materials.
Oxygen allotrope
Oxygen and ozone oxygen is one of the components of air, which is colorless, odorless and tasteless. Oxygen is heavier than air, and its density is 10 1325pa under standard conditions (0℃, atmospheric pressure) .429g/l. It is soluble in water, but its solubility is very small. When the pressure is 10 1kPa, oxygen turns into a light blue liquid at about-180℃ and turns into a snowy light blue solid at about -2 18℃. Oxygen can directly combine with many elements to form oxides. Oxygen is necessary for animals and plants to burn and breathe. Oxygen-enriched air is used for medical treatment and high-altitude flight, pure oxygen is used for steelmaking, cutting and welding metals, and liquid oxygen is used as oxidant for rocket engines. Oxygen used in production is fractionated from liquid air. Oxygen is produced by the decomposition of oxygen-containing salts (potassium chlorate, potassium permanganate, etc.). ) by heating in the laboratory. Physical properties: ① color, taste and state: colorless and odorless gas (standard state); ② Melting point: ③ Density: greater than air; ④ Water solubility: insoluble in water; ⑤ Storage: Chemical properties of sky blue steel cylinder: 1. Oxygen reacts with metal: 2mg+O2 = = 2mgo, which gives off dazzling light and gives off a lot of heat to generate white solid. 3Fe+2O = = 2Fe3O4, the red-hot iron wire burns violently, sparking, releasing a lot of heat and generating black solids. 2cu+O2 = = 2cuo, and a layer of black substance is formed on the surface of bright red copper wire after heating. 2. Oxygen reacts with nonmetals: C+O2 = = CO2, which burns violently, giving off white light and heat, and producing gas to make limewater turbid. S+O2 = = SO2, bright blue-purple flame appears, giving off heat and producing gas with pungent smell. 4p+5o2 = = 2p2o5, burning violently, giving off light, releasing heat and producing white smoke. Third, oxygen reacts with some organic substances, such as methane, acetylene, alcohol, paraffin, etc., and when burned in oxygen, water and carbon dioxide can be generated. CH4+2O = = 2co2+2h2o 2ch2+5o2 = = 4co2+2h2o oxygen is a chemical element. Chemical symbol o, atomic number 8, atomic weight 15.9994, belongs to ⅵ a group in the periodic table. Discovery of oxygen 1774 J. priestley of Britain focused sunlight with a large convex lens, and then heated mercury oxide to produce pure oxygen, which was found to support combustion and help breathing, and was called "dephosphorized air". Sweden's C.W. Scheler made oxygen by heating mercuric oxide and other oxyacid salts one year earlier than priestley, but his paper "Chemistry on Air and Fire" was not published until 1777, but they did make oxygen independently. 1774, priestley visited France and told A.-L. lavoisier how to make oxygen. The latter repeated the experiment in 1775 and called the gas in the air oxygen, which comes from the Greek word oxygen and means "acid producer". So these three scholars are all recognized oxygen discoverers in later generations. There are three stable isotopes of oxygen, namely oxygen 16, oxygen 17 and oxygen 18, among which the content of oxygen 16 accounts for 99.759%. The content of oxygen in the crust is 48.6%, ranking first. Oxygen is widely distributed on the earth, accounting for 23% in the atmosphere, and oxygen compound water is everywhere in oceans, rivers and lakes, accounting for 88.8% in water. There are many oxygenated salts on the earth, such as aluminosilicate contained in soil, and minerals such as silicate, oxide and carbonate. Oxygen in the atmosphere is constantly used for animal metabolism, and oxygen in human body accounts for 65%. Photosynthesis of plants can convert carbon dioxide into oxygen, which keeps the oxygen circulating. Although the earth is full of oxygen, it is mainly extracted from the air and there are inexhaustible resources. Physicochemically, oxygen is a colorless, odorless and tasteless gas with a melting point of -2 18.4℃, a boiling point of-182.962℃, a gas density of 1.429 g/cm3, and liquid oxygen is light blue. Oxygen is a chemically active element. Except for chlorine, bromine, iodine and some inactive metals (such as gold and platinum) in inert gas and halogen, most nonmetals can be directly oxidized and combined with gold metal, but oxygen can be indirectly combined with xenon in inert gas to form oxide: XeF6+3H2OXeO3+6HF, and chlorine oxide can also be indirectly prepared as 2Cl2+2HgOHgO. At room temperature, HgCl2+Cl2O can also oxidize other compounds: 2NO+O22NO2 O can oxidize glucose, which is the main reaction of organism respiration; The oxidation states of C6H12o6+6o26co2+6H2O are -2,-1 and +2. The oxidation of oxygen is second only to fluorine, so when oxygen reacts with fluorine, it appears as +2 valence, forming oxyfluoride (F2O). The binary compounds formed by oxygen and metal elements are oxides, peroxides and superoxides. Oxygen molecules can lose an electron, generating molecular oxygen (), forming compounds such as O2PtF6. The laboratory preparation methods of oxygen are as follows: ① thermal decomposition of potassium chlorate; (2) electrolytic water; ③ Thermal decomposition of oxides; ④ Decomposition of hydrogen peroxide with manganese dioxide as catalyst; In the spaceship, the carbon dioxide gas exhaled by astronauts can react with potassium peroxide to generate oxygen for astronauts to breathe. The method of large-scale production and application of oxygen is fractionation of liquid air. First compress the air, then freeze it into liquid air. Because the boiling points of rare gases and nitrogen are lower than that of oxygen, the remaining liquid oxygen after fractionation can be stored in high-pressure steel cylinders. All oxidation reactions and combustion processes need oxygen, such as removing impurities such as sulfur and phosphorus during steelmaking. When the mixture of oxygen and acetylene burns, the temperature is as high as 3500℃, which is used for welding and cutting steel. Oxygen is needed for glass manufacturing, cement production, mineral roasting and hydrocarbon processing. Liquid oxygen is also used as rocket fuel, which is cheaper than other fuels. People who work in anoxic or anoxic environment, such as divers and astronauts, oxygen is indispensable to maintain life. However, the active state of oxygen, such as OH and H2O2, has serious damage to biological tissues, and the damage of ultraviolet rays to skin and eyes is mostly related to this effect. As we all know, the ozone layer in the ozone atmosphere protects life on earth-it absorbs most of the ultraviolet rays released by the sun and protects animals and plants from such rays. In order to make up for the increasingly thin ozone layer and even the hole in the ozone layer, people try their best, such as promoting the use of fluorine-free refrigerants and reducing the damage of substances such as freon to ozone. The world has also set up an international day to protect the ozone layer. This gives people the impression that the more ozone you protect, the better. Actually, it's not. If there is too much ozone accumulated in the atmosphere, especially near the ground, the high ozone concentration will be a disaster for human beings. Ozone is a trace gas in the earth's atmosphere, which is formed by the decomposition of oxygen molecules in the atmosphere into oxygen atoms by solar radiation, and then the oxygen atoms combine with the surrounding oxygen molecules, containing three oxygen atoms. More than 90% of ozone in the atmosphere exists in the upper atmosphere or stratosphere, which is 50 kilometers away from the ground 10 ~ 50. This is the atmospheric ozone layer that needs human protection. There are still a few ozone molecules hovering near the ground, which can still play a certain role in blocking ultraviolet rays. However, in recent years, it has been found that the ozone concentration in the near-surface atmosphere is increasing rapidly, which is not good. Where does ozone come from? Like lead pollution and sulfide, it also comes from human activities. Cars, fuels and petrochemicals are important sources of ozone pollution. Walking in the busy streets, we often see the air is slightly light brown and has a pungent smell, which is commonly known as photochemical smog. Ozone is the main component of photochemical smog. It is not directly launched, but converted. For example, nitrogen oxides emitted by automobiles can produce ozone under suitable meteorological conditions as long as they are exposed to sunlight. With the increase of automobile and industrial emissions, ground ozone pollution has become a common phenomenon in many cities in Europe, North America, Japan and China. According to the data currently available to experts, it is predicted that by 2005, the ozone layer in the near-surface atmosphere will become the main pollutant affecting the air quality in North China. Research shows that when the ozone concentration in the air is at the level of 0.0 12ppm, which is also a typical level in many cities, it will cause people's skin itching, eyes, nasopharynx and respiratory tract irritation, and lung function will be affected, causing symptoms such as cough, shortness of breath and chest pain. The ozone level in the air rose to 0.05ppm, and the number of inpatients increased by 7% ~ 10% on average. The reason is that as a strong oxidant, ozone can react with almost any biological tissue. When ozone is inhaled into the respiratory tract, it will quickly react with cells, liquids and tissues in the respiratory tract, resulting in weakened lung function and tissue damage. For people with asthma, emphysema and chronic bronchitis, the harm of ozone is more obvious. From the nature of ozone, it can not only help people, but also harm people. It is not only an umbrella from heaven and human beings, but sometimes it is like a fierce poison. At present, people have a * * * understanding of the positive role of ozone and what measures humans should take to protect the ozone layer, and have done a lot of work. However, although people have known the negative effects of the ozone layer, there is no really feasible way to solve it except atmospheric monitoring and air pollution prediction. The principle of ozone disinfection can be considered as an oxidation reaction. (1) Mechanism of inactivation of bacteria by ozone: Ozone always inactivates bacteria very quickly. Different from other fungicides, ozone can react with the lipid double bond of bacterial cell wall, penetrate into bacteria, act on protein and lipopolysaccharide, change the permeability of cells, and lead to bacterial death. Ozone also acts on nuclear substances in cells, such as purines and pyrimidines in nucleic acids, to destroy DNA. (2) Inactivation mechanism of ozone on virus: The effect of ozone on virus is firstly the four polypeptide chains of virus capsid protein, which damages RNA, especially the protein that forms RNA. After the bacteriophage was oxidized by ozone, it was observed by electron microscope that its epidermis was broken into many fragments, from which many ribonucleic acids were released, which interfered with its adsorption on sediments. There is no doubt about the thoroughness of ozone sterilization. Destroy the ozone layer and endanger all of us. Ultraviolet rays affect human health in many ways. Sunburn, eye diseases, immune system changes, light changes and skin diseases (including skin cancer) can occur in human body. Skin cancer is a stubborn disease, and the increase of ultraviolet rays will increase the risk of this disease. Ultraviolet photons have enough energy to break the double bond. Short-and medium-wave ultraviolet rays can penetrate deep into human skin, causing skin inflammation, destroying human genetic material DNA (deoxyribonucleic acid), transforming normal growth cells into cancer cells and continuing to grow into a whole skin cancer. Others say that sunlight penetrates the surface of the skin. Ultraviolet radiation bombards the basic unit of DNA in the skin nucleus, melting many units into useless fragments. The repair process of these defects may be abnormal, which may lead to cancer. Epidemiology has confirmed that the incidence of non-melanoma skin cancer in factories is closely related to sun exposure. People with all skin types are likely to suffer from non-melanoma skin cancer, but people with light skin have a higher incidence. Animal experiments have found that ultraviolet B wavelength region is the wavelength region with the strongest carcinogenic effect. It is estimated that the total ozone will be reduced by 1% (that is, ultraviolet B will be enhanced by 2%), and the canceration rate of basic cells will be increased by about 4%. Recent studies have found that ultraviolet B can change the function of the immune system. Some experimental results show that infectious skin diseases may also be related to the enhancement of ultraviolet B caused by ozone reduction. It is estimated that the total ozone will decrease 1%, the incidence of skin cancer will increase by 5%-7%, and cataract patients will increase by 0.2%-0.6%. Since 1983, the incidence of skin cancer in Canada has increased by 235%, and the number of patients with skin diseases in 199 1 year has reached 47,000. The director of the US Environmental Protection Agency said that the number of people who died of skin cancer in the United States in the next 50 years will increase by 200,000 compared with the previous forecast. Australians like sunbathing and tanning their skin. Although scientists have repeatedly warned that more sunlight will lead to skin cancer, they still like dark skin. Results People didn't wake up until the incidence of skin cancer in Australia was 1 times higher than that in other parts of the world. People suffering from skin cancer have accounted for 1/3 of the total number of cancer patients in the world. The United Nations Environment Programme warned that if the ozone layer of the earth continues to decrease and thin at the current rate, the proportion of skin cancer in the world will increase by 26% to 300,000 by the year 2000. If the ozone layer decreases by 10% at the beginning of the next century, the number of people suffering from cataracts in the world may reach 1.6 million-1.75 million every year. Exposure to ultraviolet light may also induce measles, chickenpox, malaria, scab, mycosis, tuberculosis, leprosy and lymphoma. The increase of ultraviolet rays will also lead to the death of marine plankton, shrimp and crab larvae and shellfish, leading to the extinction of some organisms. As a result of ultraviolet radiation, groups of rabbits will suffer from myopia and thousands of sheep will be blind. Ultraviolet B weakens the function of light platform. According to experiments in coastal areas of Africa, it is speculated that the photosynthesis of plankton is weakened by about 5% under enhanced ultraviolet B irradiation. Enhanced ultraviolet B can also change the freshwater ecosystem by destroying microorganisms in water, thus weakening the self-purification ability of water. Enhanced ultraviolet B can also kill young fish, shrimps and crabs. If the original plankton in the Antarctic ocean drops extremely, the whole marine life will change greatly. However, some plankton are sensitive to ultraviolet rays, while others are not. The damage degree of ultraviolet rays to DNA of different organisms is different 100 times. It has seriously hindered the normal growth of various crops and trees. Some plants, such as peanuts and wheat, are very resistant to ultraviolet B, while others, such as lettuce, tomatoes, soybeans and cotton, are very sensitive. Trenmora of the Agricultural Biotechnology Center of the University of Maryland observed six soybean varieties with solar lights. The results showed that three soybean varieties were extremely sensitive to ultraviolet radiation. Specifically, the photosynthetic intensity of soybean leaves decreased, resulting in a decrease in yield, while soybean was planted in protein and its oil content decreased. The loss of atmospheric ozone layer 1% will also reduce soybean production 1%. Tremola also spent four years observing the effects of high-dose ultraviolet radiation on the growth of trees. The results showed that the accumulation of wood decreased obviously, and the growth of root system was also hindered. Adverse effects on global climate: A large reduction in ozone in the upper stratosphere and a corresponding increase in ozone in the lower stratosphere and upper troposphere may have adverse effects on global climate. The vertical redistribution of ozone may warm the lower atmosphere and aggravate the greenhouse effect caused by the increase of carbon dioxide. Photochemical air pollution Excessive ultraviolet rays make polymer materials such as plastics easy to age and decompose, resulting in a new pollution-photochemical air pollution. However, it should be noted that ozone and carbon dioxide have similar electrons, but different molecular structures. Ozone is linear and carbon dioxide is linear. The explanation of this requires the knowledge of inorganic chemistry in university. Recently, NASA scientists discovered that the huge ozone hole over the South Pole of the Earth changed obviously in September, from the original vortex shape to the shape of two "amoebas" with a big middle. Although the area of ozone hole seems to be shrinking in recent two years, scientists warn that it is too early to say that the ozone layer is "repairing and decreasing". Ozone experts from NASA, including Newman, said that the increase in atmospheric temperature caused the ozone hole to shrink. In 2000, the Antarctic ozone hole once reached 2.8 million square kilometers, equivalent to the area of three American continents. At the beginning of September, 2002, NASA scientists estimated that the hole was reduced to 6,543,800+500,000 square kilometers. An Australian ozone research group once reported a good news to the world: due to the effective implementation of environmental protection measures for many years, the ozone hole over Antarctica is shrinking, and it is expected that this "notorious" huge hole will be completely "filled" by 2050. It is reported that the ozone hole over Antarctica has always been one of the problems that plague environmentalists all over the world. At its worst, the ozone hole used to be three times as big as Australia. Scientists have found that the culprit of "swallowing" ozone is chlorofluorocarbons in the atmosphere-an organic compound containing chlorine, fluorine and carbon (commonly known as "freon"). In order to prevent the ozone hole from further aggravating and protect the ecological environment and human health, 1990 countries formulated the Montreal Protocol, which imposed strict restrictions on the emission of chlorofluorocarbons. Now, the unremitting efforts of environmental protection organizations for many years have finally paid off: ozone is back! Paul Frescher, an atmospheric research expert at CSIRO, Australia, said excitedly, "This is a big news. We have been looking forward to this day for a long time! " He said that although there are still many factors affecting the shrinking process of the ozone hole, such as the greenhouse effect and climate change, "we have come to the conclusion that the ozone hole over Antarctica will disappear completely in less than 50 years after considering all the factors comprehensively."
[Edit this paragraph] The difference between allotrope and isotope
Allomorphism refers to different simple substances of the same element. They are simple substances, in other words, they are substances. For example, graphite and diamond are both substances, right? Not just an element? So they are allotropes. Isotopes are the same element with different numbers of neutrons but the same number of protons. They are just elements, such as H 1 without neutrons and h12 and C 14 with neutrons. Then they are just elements. They are not separate substances, so they are isotopes. H2 and H3, H3 are three hydrogen atoms, and H2 is two hydrogen atoms, so they are different substances, and they are allotropes. If you mean that H3 refers to element H with mass number 3, then they are elements or isotopes.
[Edit this paragraph] Heterogeneous
Isomerization means that organic compounds have the same molecular formula, however, they have different structures. Common heterogeneous types are 1. The isomerization of carbon chains is caused by the different shapes of carbon chains in molecules, such as n-butane and isobutane. 2. positional isomerization is caused by different positions of substituents or functional groups on carbon chains or carbon rings, such as 1- butyne and 2- butyne 1- propanol and 2- propanol 3. Isomerization due to different functional groups in the molecule, such as: monoolefins and cycloalkanes, alcohols and ethers, aldehydes and ketones, alkynes and dienes, esters and carboxylic acids, phenols and aromatic alcohols. 4. Stereoisomerism: the structure is similar, but a slight deviation leads to different structures (1). Cis-trans isomerization: a stereoisomerism phenomenon, which occurs because the double bond cannot rotate freely, generally referring to the double bond of olefin or aromatic alcohol. (2) Optical isomerism: constructing the same molecule, such as polarizing one side to the right and the other side to the left. Then the two are optical isomers of each other. 5. Conformational isomorphism: The conformation of the same compound can be changed from one to the other by single bond rotation, so they are conformational isomers.