The main difference between them is their composition. Thus, simple substances include atoms of one element. Their (simple substances) crystals can be synthesized in the laboratory, and sometimes at home. However, it is often necessary to create certain conditions for storing the resulting crystals.
There are five classes into which simple substances are divided: metals, semimetals, nonmetals, intermetallic compounds, and halogens (not found in nature). They can be represented by atomic (Ar, He) or molecular (O2, H2, O3) gases.
As an example, we can take the simple substance oxygen. It includes molecules consisting of two atoms of the element Oxygen. Or, for example, the substance iron consists of crystals containing only atoms of the element Iron. Historically, it was customary to name a simple substance by the name of the element whose atoms are included in its composition. The structure of these compounds can be molecular or non-molecular.
Complex substances include atoms various types and upon decomposition can form two (or more) compounds. For example, when water splits, it forms oxygen and hydrogen. However, not every compound can be broken down into simple substances. For example, iron sulfide, formed by sulfur and iron atoms, cannot be broken down. In this case, in order to prove that the compound is complex and includes dissimilar atoms, the reverse reaction principle is used. In other words, iron sulfide is obtained using the starting components.
Simple substances are forms of chemical elements that exist in free form. Today science knows more than four hundred types of these elements.
Unlike complex substances, simple substances cannot be obtained from other simple substances. They also cannot be decomposed into other compounds.
All allotropic modifications have the property of transforming into each other. Different types simple substances formed by one chemical element can have different and different levels chemical activity. For example, oxygen exhibits less activity than ozone, and the melting point of fullerene, for example, is lower than that of diamond.
IN normal conditions for eleven elements the simple substances will be gases (Ar, Xe, Rn, N, H, Ne, O, F, Kr, Cl, He,), for two liquids (Br, Hg), and for other elements - solids.
At temperatures close to room temperature, the five metals will take on a liquid or semi-liquid state. This is due to the fact that their melting point is almost equal. Thus, mercury and rubidium melt at 39 degrees, francium at 27, cesium at 28, and gallium at 30 degrees.
It should be noted that the concepts of “chemical element”, “atom”, “simple substance” should not be confused. So, for example, an atom has a certain specific meaning and it really exists. The definition of “chemical element” is generally abstract and collective. In nature, elements are present in the form of free or chemically bonded atoms. At the same time, the characteristics of simple substances (collections of particles) and chemical elements (isolated atoms) specific type) have their own characteristics.
Ticket 1:
Chemistry is the science of substances, their structure and properties, as well as the transformation of some substances into others. A chemical element is certain type atoms with the same positive charge kernels. A chemical element exists in three forms: 1) a single atom; 2) simple substances; 3) complex substances or chemical compounds. Substances formed by one chemical element are called simple. Substances formed by several chemical elements are called complex
Ticket 2:
Human life depends on chemistry - the processes of breaking down food in the body are continuous chemical reaction. Well, everything we wear, what we travel in, what we look at one way or another goes through certain stages. chemical treatment- be it painting, making various alloys, etc. Chemistry plays a big role in industry. Both heavy and light. For example: without chemistry, a person would not be able to obtain medicines and some food products non-natural origin (vinegar). By by and large- chemistry inside and around us. Chemical industry- one of the most violent emerging industries. It belongs to the industries that form the basis of modern scientific and technological progress(plastics, chemical fibers, dyes, pharmaceuticals, detergents and cosmetics). As a result economic activity person changes gas composition and dustiness of the lower layers of the atmosphere. As a result, this can cause a long-term effect on a person: chronic inflammatory diseases of various organs, changes nervous system, an effect on the intrauterine development of the fetus, leading to various abnormalities in newborns. Ecological problems can only be solved with stabilization economic situation and the creation of such an economic mechanism for environmental management, when payment for pollution environment will correspond to the cost of its complete cleaning.
Ticket 3:
The most famous:
Dmitry Ivanovich Mendeleev, of course, with his famous periodic system of chemical elements.
KUCHEROV MIKHAIL GRIGORIEVICH - Russian organic chemist, discovered the reaction of the catalytic hydration of acetylene hydrocarbons with the formation of carbonyl-containing compounds, in particular, the conversion of acetylene into acetaldehyde in the presence of mercury salts.
KONOVALOV MIKHAIL IVANOVICH - Russian organic chemist, discovered the nitrating effect of a weak solution nitric acid on limiting hydrocarbons, developed methods for the isolation and purification of naphthenes.
LEBEDEV SERGEY VASILIEVICH - Russian chemist, first obtained a sample of synthetic butadiene rubber, received synthetic rubber polymerization of butadiene under the influence of sodium metal. Thanks to Lebedev, since 1932, a domestic synthetic rubber industry began to be created in our country.
Ticket 4: Type of element, what element, information about it (number of electron layers, number of electrons per external level, degree of deposition, number of protons/neutrons/electrons, relative mass, element group, configuration of the outer layer), reaction - interaction of elements, substances, formulas - substances and classes of substances.
Ticket 5: An atom consists of atomic nucleus and particles (electrons, protons, neutrons) located on the periphery. Protons and neutrons make up the nucleus of an atom, which carries almost all the mass of the atom. Electrons make up electron shell atom, which is divided into energy levels (1,2,3, etc.), the levels are divided into sublevels (denoted by the letters s, p, d, f). The sublevels consist of atomic orbitals, i.e. regions of space where electrons are likely to reside. Orbitals are designated as 1s (orbital of the first level, s-sublevel) The filling of atomic orbitals occurs in accordance with three conditions: 1) The principle of minimum energy
2) The exclusion rule, or the Pauli principle
3) The principle of maximum multiplicity, Hund's rule.
Isotopes are atoms of the same element that differ in the number of neutrons in the nucleus.
For example, most a shining example there may be isotopes of hydrogen:
1H - protium with one proton in the nucleus and 1 electron in the shell
2H - deuterium with one proton and one neutron in the nucleus and one electron in the shell
3H - tritium with one proton and two neutrons in the nucleus and one electron in the shell
Ticket 6:
1. H)1
2. He)2
3. Li)2)1
4. Be)2)2
5. B)2)3
6. C)2)2
7. N)2)5
8. O)2)6
9. F)2)7
10. Ne)2)8
11. Na)2)8)1
12. Mg)2)8)2
13. Al)2)8)3
14. Si)2)8)4
15. P)2)8)5
16. S)2)8)6
17. Cl)2)8)7
18. Ar)2)8)8
19. K)2)8)8)1
20. Ca)2)8)8)8
At the external level, if there are 2 or 8 electrons, it is complete, and if there is a different number, it is not complete.
Ticket 8:
Ionic bond these are: typical metal + typical non-metal. Example: NaCl, AlBr3. Covalent polar is: nonmetal + nonmetal (different). Example: H2O, HCl. Covalent nonpolar is: nonmetal + nonmetal (identical). Example: H2, Cl2, O2, O3. And metallic when metal + metal Li, Na, K
Ticket 11:
Complex substances consist of organic and inorganic substances.
Inorganic substances: Oxides, hydroxides, salts
Organic substances: acids, bases.
Well, my friend, I helped with whatever I could.)
Organic and inorganic substances;
> recognize metals and non-metals;
> identify metallic and non-metallic elements according to their location in periodic table D. I. Mendeleev; understand why all metals have similar properties.
Atoms under ordinary conditions cannot exist alone for long. They are able to combine with the same or other atoms, which causes a wide variety of substances in the world.
A substance formed by one chemical element is called simple, and a substance formed by several elements is called a complex or chemical compound.
Simple substances
Simple substances are divided into metals and non-metals. This classification of simple substances was proposed by the outstanding French scientist A.L. Lavoisier in late XVIII V. The chemical elements from which metals come are called metallic, and those that form non-metals are called
non-metallic. In the long version of D.I. Mendeleev’s system (endpaper II), they are delimited by a broken line. Metal elements are to the left of it; there are significantly more of them than non-metallic ones.
This is interesting
Simple substances of 13 elements - Au, Ag, Cu, Hg, Pb, Fe, Sn, Pt, S, C, Zn, Sb and As were known in ancient times.
Each of you can, without hesitation, name several metals (Fig. 36). They differ from other substances by a special “metallic” luster. These substances have a lot general properties.
Rice. 36. Metals
Metals under normal conditions are solids (only mercury is a liquid), conduct electricity and heat well, and have generally high temperature melting (over 500 °C).
Rice. 37. Simplified model internal structure metal
They are plastic; they can be forged and wire drawn from them.
Thanks to their properties, metals have confidently entered people's lives. About them of great importance the names indicate historical eras: copper age, Bronze 1st Age, Iron Age.
The similarity of metals is due to their internal structure.
Structure of metals. Metals are crystalline substances. The crystals in metals are much smaller than sugar or table salt crystals and cannot be seen with the naked eye.
Molecule - an electrically neutral particle consisting of two or more connected atoms.
In each molecule, the atoms are connected to each other quite strongly, but the molecules are connected to each other in a substance very weakly. Therefore, substances of molecular structure do not have high temperatures melting and boiling.
Oxygen and ozone are molecular substances. These are simple oxygen substances. An oxygen molecule contains two Oxygen atoms, and an ozone molecule contains three (Fig. 39).
Rice. 39. Models of molecules
Not only oxygen, but also many other elements form two or more simple substances. Therefore, there are several times more simple substances than chemical elements.
Names of simple substances.
Most simple substances are named after the corresponding elements. If the names are different, then they are given in the periodic table, with the name of the simple substance located below the name
element (Fig. 40).
Name the simple substances of the elements Hydrogen, Lithium, Magnesium, Nitrogen.
1 The term "molecule" comes from Latin word moles (mass), diminutive suffix cula and translated means “small mass”.
The names of simple substances are written inside the sentence with a small letter.
Rice. 40. Cell of the periodic table
Complex substances (chemical compounds)
The combination of atoms of different chemical elements gives rise to many complex substances(there are tens of thousands of times more of them than simple ones).
There are complex substances with molecular, atomic and ionic structure. Therefore, their properties are very different.
Molecular compounds are mostly volatile and often have an odor. Their melting and boiling points are significantly lower than those of compounds with an atomic or ionic structure.
The molecular substance is water. A water molecule consists of two Hydrogen atoms and one Oxygen atom (Fig. 41).
Rice. 41. Water molecule model
The molecular structure is carbon monoxide and carbon dioxide. gases, sugar, starch, alcohol, acetic acid etc. The number of atoms in the molecules of complex substances can be different - from two atoms to hundreds and even thousands.
Some connections have atomic structure.
One of them is the mineral quartz, the main component of sand. It contains Silicium and Oxygen atoms (Fig. 42).
Rice. 42. Model of compound of atomic structure (quartz)
There are also ionic compounds. This - salt, chalk, soda, lime, gypsum and many others. Table salt crystals consist of positively charged Sodium ions and negatively charged Chlorine ions (Fig. 43). Each such ion is formed from the corresponding atom (§ 6).
Rice. 43. Model ionic compound(table salt)
This is interesting
In molecules organic compounds In addition to Carbon atoms, as a rule, there are also Hydrogen atoms, often Oxygen atoms, and sometimes some other elements.
The mutual attraction of many oppositely charged ions causes the existence of ionic compounds.
An ion formed from one atom is called simple, and an ion formed from several atoms is called complex.
Positively charged simple ions exist for metal elements, and negatively charged - for non-metallic elements.
Names of complex substances.
The textbook has so far provided technical or household names complex substances. In addition, substances also have chemical names. For example, chemical name table salt is sodium chloride, and chalk is calcium carbonate. Each such name consists of two words. The first word is the name of one of the elements that form the substance (it is written with a small letter), and the second comes from the name of another element.
Organic and inorganic substances.
Previously, organic substances were those substances that are found in living organisms. These are proteins, fats, sugar, starch, vitamins, compounds that give color, smell, taste to vegetables and fruits, etc. Over time, scientists began to obtain in laboratories substances similar in composition and properties that do not exist in nature. Nowadays, organic substances are called carbon compounds (with the exception of carbon dioxide and carbon dioxide, chalk, soda, and some others).
Most organic compounds are capable of burning, and when heated in the absence of air, they become charred (coal consists almost entirely of carbon atoms).
K not organic matter belong to the remaining complex substances, as well as all simple ones. They form the basis of the mineral world, i.e. they are found in soil, minerals, rocks, air, natural water. In addition, inorganic substances are also found in living organisms.
The material in this paragraph is summarized in Diagram 6.
Laboratory experiment No. 2
Introduction to substances various types
You have been given the following substances (the option will be indicated by the teacher):
option I - sugar, calcium carbonate (chalk), graphite, copper;
option II - paraffin, aluminum, sulfur, sodium chloride (table salt).
The substances are in jars with labels.
Carefully examine the substances, pay attention to their names. Identify among them simple (metals, non-metals) and complex substances, as well as organic and inorganic.
Enter the name of each substance in the table and indicate its type by writing a “+” sign in the appropriate columns.
conclusions
Substances can be simple and complex, organic and inorganic.
Simple substances are divided into metals and non-metals, and chemical elements- metallic and non-metallic.
Metals have many common properties due to the similarity of their internal structure.
Nonmetals are made up of atoms or molecules and have different properties from metals.
Complex substances (chemical compounds) have an atomic, molecular or ionic structure.
Almost all Carbon compounds belong to organic substances, and the remaining compounds and simple substances belong to inorganic substances.
?
56. Which substance is called simple and which is called complex? What types of simple substances exist and what are the names of the corresponding elements?
57. According to what physical properties Can a metal be distinguished from a non-metal?
58. Define a molecule. How does a molecule of a simple substance differ from a molecule of a complex substance?
59. Fill in the blanks by inserting the words “Nitrogen” or “nitrogen” in the appropriate cases and explain your choice:
a) ... is the gas that contains the largest amount in the air;
b) a molecule... consists of two atoms...;
c) compounds... enter plants from the soil;
d)... is poorly soluble in water.
60. Fill in the blanks by inserting the words “element”, “atom” or “molecule” in the appropriate case and number:
A)... white phosphorus contains four... Phosphorus;
b) there is... carbon dioxide in the air;
c) gold is a simple substance... Aurum.
Under chemical element understand a collection of atoms with the same positive nuclear charge and with a certain set of properties. Atoms of the same chemical element combine to form simple substance. When atoms of different chemical elements combine, complex substances (chemical compounds) or mixtures. Difference chemical compounds from mixtures is that:
They have new properties that the simple substances from which they were obtained did not have;
They cannot be mechanically divided into their component parts;
Chemical elements in their composition can only be in strictly defined quantitative ratios.
Some chemical elements (carbon, oxygen, phosphorus, sulfur) can exist in the form of several simple substances. This phenomenon is called allotropy, and varieties of simple substances of the same chemical element are called its allotropic modifications(modifications).
Tasks
1.1. What more exists in nature: chemical elements or simple substances? Why?
1.2. Is it true that sulfur and iron are included in the composition of iron sulfide as substances? If not, what is the correct answer?
1.3. Name allotropic modifications of oxygen. Do they differ in their properties? If so, how?
1.4. Which of the allotropic modifications of oxygen is chemically more active and why?
1.5. The simple substances or chemical elements are zinc, sulfur and oxygen in the following reactions:
1) CuSO 4 + Zn = ZnSO 4 + Cu;
2) S + O 2 = SO 2;
3) Zn + 2HC1 = ZnCl 2 + H 2 ;
4) Zn + S = ZnS;
5) 2H 2 0 = 2H 2 + O 2 .
1.6. Is it possible to get another simple substance from one simple substance? Give a reasoned answer.
1.7. When a substance is burned in oxygen, sulfur (IV) oxide, nitrogen and water are produced. What chemical elements form the starting substance?
1.8. Indicate whether simple or complex substances include: H 2 O, C1 2, NaOH, O 2, HNO 3, Fe, S, ZnSO 4, N 2, AgCl, I 2, A1 2 O 3, O 3?
1.9. For which chemical elements are allotropic modifications known? Name these modifications.
1.10. Is it possible for a chemical element to transition from one allotropic modification to another? Give examples.
1.11. What chemical elements do they mean when they talk about diamond and ozone?
1.12. Which of the substances are chemical compounds and which are mixtures:
2) air;
4) sulfuric acid;
1.13. How to prove that sodium chloride is a complex substance?
1.14. Name three allotropic modifications of carbon.
1.15. What are allotropic modifications of phosphorus called and how do they differ from each other?
1.16. What are allotropic modifications of sulfur called and how do they differ from each other?
1.17. Indicate which of the statements is true and why - the composition of barium sulfate includes:
1) simple substances barium, sulfur, oxygen;
2) chemical elements barium, sulfur, oxygen.
1.18. How many liters of ammonia can be produced from a mixture of 10 liters of nitrogen and 30 liters of hydrogen?
1.19. How many liters of water vapor are produced from a mixture of 10 liters of hydrogen and 4 liters of oxygen? What gas and in what volume will remain in excess?
1.20. How many grams of zinc sulfide (ZnS) can be formed from a mixture of 130 g of zinc and 48 g of sulfur?
1.22. What is a solution of alcohol in water - a mixture or a chemical compound?
1.23. Can a complex substance consist of atoms of the same type?
1.24. Which of the following substances are mixtures and which are chemical compounds:
1) bronze;
2) nichrome;
3) kerosene;
4) potassium nitrate:
5) rosin;
6) superphosphate.
1.25. Given a mixture of Cl 2 + HCl + CaCl 2 + H 2 O.
1) How many different substances are in the mixture;
2) How many chlorine molecules are in the mixture;
3) How many chlorine atoms are in the mixture;
4) How many molecules of different substances are contained in the mixture.
IN previous chapter it was said that not only atoms of one chemical element can form bonds with each other, but also atoms different elements. Substances formed by atoms of one chemical element are called simple substances, and substances formed by atoms of different chemical elements are called complex substances. Some simple substances have molecular structure, i.e. consist of molecules. For example, substances such as oxygen, nitrogen, hydrogen, fluorine, chlorine, bromine, iodine have a molecular structure. Each of these substances is formed by diatomic molecules, so their formulas can be written as O 2, N 2, H 2, F 2, Cl 2, Br 2 and I 2, respectively. As you can see, simple substances can have the same name as the elements that form them. Therefore, it is necessary to clearly distinguish between situations when we're talking about about a chemical element, and when about a simple substance.
Often simple substances have not a molecular, but an atomic structure. In such substances, atoms can form bonds of various types with each other, which will be discussed in detail a little later. Substances of a similar structure are all metals, for example, iron, copper, nickel, as well as some non-metals - diamond, silicon, graphite, etc. These substances are usually characterized not only by the coincidence of the name of the chemical element with the name of the substance formed by it, but also by the identical recording of the formula of the substance and the designation of the chemical element. For example, the chemical elements iron, copper and silicon, designated Fe, Cu and Si, form simple substances whose formulas are Fe, Cu and Si, respectively. There is also a small group of simple substances consisting of isolated atoms that are not connected in any way. Such substances are gases, which are called noble gases due to their extremely low chemical activity. These include helium (He), neon (Ne), argon (Ar), krypton (Kr), xenon (Xe), radon (Rn).
Since there are only about 500 known simple substances, the logical conclusion follows that many chemical elements are characterized by a phenomenon called allotropy.
Allotropy is a phenomenon when one chemical element can form several simple substances. Different chemical substances formed by one chemical element are called allotropic modifications or allotropes.
So, for example, the chemical element oxygen can form two simple substances, one of which has the name of the chemical element - oxygen. Oxygen as a substance consists of diatomic molecules, i.e. its formula is O 2. It is this compound that is part of the air we need for life. Another allotropic modification of oxygen is the triatomic gas ozone, whose formula is O 3 . Despite the fact that both ozone and oxygen are formed by the same chemical element, they chemical behavior very different: ozone is much more active than oxygen in reactions with the same substances. In addition, these substances differ from each other in physical properties, at least due to the fact that molecular mass ozone is 1.5 times greater than oxygen. This leads to the fact that its density is gaseous state also 1.5 times more.
Many chemical elements tend to form allotropic modifications that differ from each other in the structural features of the crystal lattice. So, for example, in Figure 5, you can see schematic images of fragments crystal lattices diamond and graphite, which are allotropic modifications of carbon.
Figure 5. Fragments of crystal lattices of diamond (a) and graphite (b)
In addition, carbon can also have a molecular structure: such a structure is observed in a type of substance such as fullerenes. Substances of this type formed by spherical carbon molecules. Figure 6 shows 3D models of a c60 fullerene molecule and a soccer ball for comparison. Notice their interesting similarities.
Figure 6. C60 fullerene molecule (a) and soccer ball (b)
Complex substances are substances that consist of atoms of different elements. They, just like simple substances, can have molecular and non-molecular structure. The non-molecular type of structure of complex substances can be more diverse than that of simple ones. Any complex chemical substances can be obtained either by direct interaction of simple substances or by a sequence of their interactions with each other. It is important to realize one fact, which is that the properties of complex substances, both physical and chemical, are very different from the properties of the simple substances from which they are obtained. For example, table salt, which has NaCl forum and is colorless clear crystals, can be obtained by the interaction of sodium, which is a metal with properties characteristic of metals (brilliance and electrical conductivity), with chlorine Cl 2, a yellow-green gas.
Sulfuric acid H 2 SO 4 can be formed by a series of successive transformations from simple substances - hydrogen H 2, sulfur S and oxygen O 2. Hydrogen is a gas lighter than air that forms explosive mixtures with air, sulfur is solid yellow color, capable of burning, and oxygen is a gas slightly heavier than air in which many substances can burn. Sulfuric acid, which can be obtained from these simple substances, is a heavy oily liquid with strong water-removing properties, due to which it chars many substances of organic origin.
It is obvious that in addition to individual chemical substances, there are also mixtures of them. The world around us is formed primarily by mixtures of various substances: metal alloys, food products, drinks, various materials, of which the objects around us are made.
For example, the air we breathe consists mainly of nitrogen N2 (78%), oxygen (21%), which is vital for us, and the remaining 1% consists of impurities of other gases ( carbon dioxide, noble gases and etc.).
Mixtures of substances are divided into homogeneous and heterogeneous. Homogeneous mixtures are those mixtures that do not have phase boundaries. Homogeneous mixtures are a mixture of alcohol and water, metal alloys, a solution of salt and sugar in water, mixtures of gases, etc. Heterogeneous mixtures are those mixtures that have a phase boundary. Mixtures of this type include a mixture of sand and water, sugar and salt, a mixture of oil and water, etc.
The substances that make up mixtures are called components.
Mixtures of simple substances, unlike chemical compounds that can be obtained from these simple substances, retain the properties of each component.
