s-, p-Elements are located in the main subgroups periodic system DI. Mendeleev (subgroup A). Each period begins with two s-elements, and the last six (except for the first period) are p-elements. In s- and p-elements, the electrons and orbitals of the outer layer of the atom are valence. The number of outer electrons is equal to the group number (except for and ). With the participation in the formation of bonds of all valence electrons, the element exhibits the highest degree of oxidation, which is numerically equal to the group number. Compounds in which the elements of odd groups exhibit odd oxidation states, and the elements of even groups exhibit even oxidation states are energetically more stable (Table 8).

s-Elements. Atoms s 1 elements have a single electron at the last level and show an oxidation state of only +1, are strong reducing agents, the most active metals. The connections are dominated ionic bond. They form oxides with oxygen. Oxides are formed with a lack of oxygen or indirectly, through peroxides and superoxides (exception). Peroxides and superoxides are strong oxidizing agents. Oxides correspond to strong soluble bases - alkalis, therefore s 1 elements are called alkali metals . Alkali metals actively react with water according to the scheme:. Metal salts s 1 are generally highly soluble in water.

s-Elements of group II show an oxidation state of +2. These are also quite active metals. In air, they oxidize to oxides, which correspond to bases. The solubility and basic nature of the bases increase from to. The compound exhibits amphoteric properties (Tables 8, 9). Beryllium does not react with water. Magnesium interacts with water when heated, the rest of the metals react according to the scheme: forming alkalis and are called alkaline earth.

Alkaline and some alkaline earth metals due to high activity, they cannot be in the atmosphere and are stored in special conditions.

When interacting with hydrogen, s-elements form ionic hydrides, which undergo hydrolysis in the presence of water:

p-elements contain from 3 to 8 electrons at the last level. Most p-elements are non-metals. For typical non-metals electron shell close to completion, i.e. they are able to accept electrons to the last level (oxidizing properties). The oxidative power of elements increases in a period from left to right, and in a group from bottom to top. The strongest oxidizing agents are fluorine, oxygen, chlorine, bromine. Non-metals can also exhibit reducing properties (except for F 2), for example:

;

Hydrogen, boron, carbon, silicon, germanium, phosphorus, astatine, tellurium show predominantly reducing properties. Examples of compounds with a negative oxidation state of a non-metal: borides, carbides, nitrides, sulfides, etc. (Table 9).

Under certain conditions, non-metals react with each other, resulting in compounds with covalent bond, for example . Non-metals form volatile compounds with hydrogen (excl.). Hydrides of groups VI and VII in aqueous solutions exhibit acidic properties. When ammonia is dissolved in water, a weak base is formed.

The p-elements located to the left of the boron-astatine diagonal are metals. Them metallic properties are much weaker than those of the s-elements.

P-elements form oxides with oxygen. Non-metal oxides are acidic in nature (excl. - non-salt-forming). P-metals are characterized by amphoteric compounds.

Acid-base properties change periodically, for example, in period III:

oxides
hydroxides
the nature of the connections	amphoteric	weak acid	medium strength acid	strong acid	very strong acid

Many p-elements can exhibit a variable oxidation state, forming oxides and acids of various compositions, for example:

Acidic properties increase with increasing oxidation state. For example, an acid is stronger, stronger, - amphoteric, - acid oxide.

Acids formed by elements in the highest oxidation state are strong oxidizing agents.

d-Elements also called transitional. They are located in large periods, between the s- and p-elements. In d-elements, nine orbitals that are energetically close are valence.

On the outer layer are 1-2 e electron (ns), the rest are located in the pre-external (n-1)d layer.

Examples electronic formulas: .

Such a structure of elements determines general properties. Simple substances formed by transition elements are metals . This is due to the presence of one or two electrons in the outer level.

The presence of partially filled d-orbitals in the atoms of d-elements causes them to variety of oxidation states . For almost all of them, the oxidation state +2 is possible - according to the number of external electrons. The highest oxidation state corresponds to the group number (with the exception of iron, elements of the subgroup of cobalt, nickel, copper). Compounds with the highest degree of oxidation are more stable, similar in form and properties to similar compounds of the main subgroups:

Oxides and hydroxides of this d-element in different oxidation states have different acid-base properties. There is a pattern: with an increase in the degree of oxidation, the nature of the compounds changes from basic through amphoteric to acidic . For example:

degree of oxidation.
oxides
hydroxides
properties	main	amphoteric	acidic

Due to the diversity of oxidation states for the chemistry of d-elements characterized by redox reactions. IN higher degrees In the oxidation state, the elements exhibit oxidizing properties, and in the +2 oxidation state, they are reducing. In an intermediate degree, compounds can be both oxidizing and reducing agents.

d-elements have a large number of vacant orbitals and therefore are good complexing agents respectively, are part of complex compounds. For example:

– potassium hexacyanoferrate (III);

– sodium tetrahydroxozincate (II);

– diamminesilver(I) chloride;

- trichlorotriaminecobalt.

test questions

261. Describe laboratory and industrial methods for producing hydrogen. What oxidation state can hydrogen exhibit in its compounds? Why? Give examples of reactions in which gaseous hydrogen plays the role of a) an oxidizing agent; b) reducing agent.

262. What compounds of magnesium and calcium are used as binding building materials? What causes their astringent properties?

263. What compounds are called quicklime and slaked lime? Write the reaction equations for their production. What compound is formed when quicklime is calcined with coal? What is the oxidizing and reducing agent in the last reaction? Write electronic and molecular equations.

264. Write chemical formulas the following substances: caustic soda, crystal soda, soda ash, potash. Explain why aqueous solutions of all these substances can be used as degreasers.

265. Write the equation for the hydrolysis of sodium peroxide. What is a sodium peroxide solution called in engineering? Will the solution retain its properties if it is boiled? Why? Write the corresponding reaction equation in electronic and molecular form.

266. On what properties of aluminum is its use based a) as a structural material; b) to obtain aerated concrete; c) in the composition of thermites during cold welding. Write the reaction equations.

267. What is the aggressiveness of natural and industrial water in relation to aluminum and aluminous cement? Write the corresponding reaction equations.

268. What compounds are called carbides? What groups are they divided into? Write the reaction equations for the interaction of calcium and aluminum carbides with water, where are they used?

269. Write the reaction equations that can be used to carry out the following transformations:

What is corrosive carbon dioxide?

270. Why is tin dissolved in hydrochloric acid and lead in nitric acid? Write the corresponding reaction equations in electronic and molecular form.

271. Make up the equations of the reactions that must be carried out to carry out the transformations:

Where are these substances used in technology?

272. Make up the molecular and electronic equations for the reactions of the interaction of ammonia and hydrazine with oxygen, where are these reactions applied?

273. What properties does sulfuric acid exhibit in redox reactions? Write in molecular and electronic form the equations of the following interactions: a) dilute sulfuric acid with magnesium; b) concentrated sulfuric acid with copper; c) concentrated sulfuric acid with coal.

274. The following methods can be used to remove sulfur dioxide from flue gases: a) adsorption on solid magnesium oxide; b) conversion to calcium sulfate by reaction with calcium carbonate in the presence of oxygen; c) transformation into free sulfur. What kind Chemical properties exhibits sulfur dioxide in these reactions? Write the corresponding equations. Where can the resulting products be used?

275. What are the special properties of hydrofluoric acid? Make up the equations of the reactions that must be carried out to carry out the transformations:

Give the substance a name. Where are transformation data used?

276. When chlorine reacts with slaked lime, bleach is formed. Write the reaction equation, indicate the oxidizing agent, reducing agent. Give chemical name received product, write it structural formula. Where is bleach used?

277. Consider the features of d-elements using the example of manganese and its compounds. Support your answer with reaction equations. For redox reactions, make an electronic balance, indicate the oxidizing agent and reducing agent.

278. Which base is stronger? Why? What properties does it exhibit when fused with alkali and basic oxides? Write some examples of obtaining such compounds. What are the resulting products called?

279. What iron salts find the greatest practical application, where and what are they used for? Support your answer with reaction equations.

280. Give the names of the substances, make the equations of the reactions that must be carried out to carry out the transformations:

for redox reactions, make electronic equations, indicate the oxidizing agent, reducing agent. What medium should be maintained during precipitation of chromium(III) hydroxide? Why?

1) s-block in the periodic table of elements - an electron shell that includes the first two layers of s-electrons. This block includes alkali metals, alkaline earth metals, hydrogen and helium. These elements differ in that in the atomic state, a high-energy electron is located in the s-orbital. With the exception of hydrogen and helium, these electrons are very easily transferred and formed into positive ions in a chemical reaction. The configuration of helium is chemically very stable, hence why helium does not have stable isotopes; sometimes, due to this property, it is combined with inert gases. The remaining elements that have this block, without exception, are strong reducing agents and therefore do not occur in nature in a free form. An element in metallic form can only be obtained by electrolysis of a salt dissolved in water. Davy Humphry, in 1807 and 1808, was the first to detach acid salts from the s-block metals, with the exception of lithium, beryllium, rubidium, and cesium. Beryllium was first separated from salts independently by two scientists: F. Wooler and A. A. Bazi in 1828, while lithium was separated only in 1854 by R. Bunsen, who, after studying rubidium, separated it 9 years later. Cesium was not isolated in its pure form until 1881, after Carl Setterberg electrolyzed cesium cyanide. The hardness of elements having an s-block in a compact form (under normal conditions) can vary from very small (all alkali metals - they can be cut with a knife) to quite high (beryllium). With the exception of beryllium and magnesium, the metals are very reactive and can be used in alloys with lead in small quantities (<2 %). Бериллий и магний, ввиду их высокой стоимости, могут быть ценными компонентами для деталей, где требуется твёрдость и лёгкость. Эти металлы являются чрезвычайно важными, поскольку позволяют сэкономить средства при добыче титана, циркония, тория и тантала из их минеральных форм; могут находить своё применение как восстановители в органической химии.

Hazard and storage

All elements having an s-shell are hazardous substances. They are flammable, require special fire extinguishing, excluding beryllium and magnesium. Should be stored in an inert atmosphere of argon or hydrocarbons. React violently with water, the reaction product is hydrogen, for example:

Excluding magnesium, which reacts slowly, and beryllium, which only reacts when its oxide film is removed with mercury. Lithium has similar properties to magnesium, as it is, relative to the periodic table, next to magnesium.

The p-block in the periodic table of elements is the electron shell of atoms whose valence electrons occupy the p-orbital with the highest energy.

The p-block contains the last six groups, excluding helium (which is in the s-block). This block contains all non-metals (excluding hydrogen and helium) and semi-metals, as well as some metals.

The P-block contains elements that have different properties, both physical and mechanical. P-block non-metals are, as a rule, highly reactive substances with strong electronegativity, p-metals are moderately active metals, and their activity increases towards the bottom of the table of chemical elements

Properties of d- and f-elements. Give examples.

The D-block in the periodic table of elements is the electron shell of atoms whose valence electrons occupy the d-orbital with the highest energy.

This block is part of the periodic table; it includes elements from 3 to 12 groups. The elements of this block fill the d-shell with d-electrons, which for the elements begins with s2d1 (the third group) and ends with s2d10 (the twelfth group). However, there are some violations in this sequence, for example, in chromium s1d5 (but not s2d4), the entire eleventh group has the configuration s1d10 (but not s2d9). The eleventh group has filled s- and d-electrons.

D-block elements are also known as transition metals or transition elements. However, the exact boundaries separating transition metals from other groups of chemical elements have not yet been drawn. Although some authors believe that the elements included in the d-block are transition elements in which d-electrons are partially filled either in neutral atoms or ions, where the oxidation state is zero. IUPAC currently accepts such studies as reliable, and reports that this applies only to 3-12 groups of chemical elements. The metals of the 12th group do not have clearly expressed chemical and physical properties, this is due to the incomplete filling of the d subshell, so they can also be considered post-transition metals. The historical use of the term "transition elements" and the d-block has also been revised.

In the s-block and p-block of the periodic table, similar properties, as a rule, are not observed through periods: the most important properties are enhanced vertically at the lower elements of these groups. It is noteworthy that the differences between the elements included in the d-block horizontally, through periods, become more pronounced.

Lutetium and lawrencium are in the d-block and are not considered transition metals, but the lanthanides and actinides, remarkably, are considered as such by IUPAC. Although the twelfth group of chemical elements is in the d-block, it is believed that the elements included in it are post-transition elements.

The p-elements of the periodic system include elements with a valence p-sublevel. These elements are located in III, IV, V, VI, VII, VIII groups, main subgroups. In a period, the orbital radii of atoms decrease with increasing atomic number, but generally increase. In subgroups of elements, as the element number increases, the sizes of atoms generally increase rather than decrease. p-elements of group III Group III p-elements include gallium Ga, indium In and thallium Tl. By the nature of these elements, boron is a typical non-metal, the rest are metals. Within the subgroup, a sharp transition from non-metal to metals can be traced. The properties and behavior of boron are similar, which is the result of the diagonal affinity of elements in the periodic system, according to which a shift in the period to the right causes an increase in the non-metallic character, and down the group - a metallic one, therefore elements similar in properties turn out to be located diagonally side by side, for example Li and Mg, Ber and Al, B and Si.

The electronic structure of the valence sublevels of Group III p-element atoms in the ground state has the form ns 2 np 1 . In compounds, boron and trivalent, gallium and indium, in addition, can form compounds with +1, and for thallium the latter is quite characteristic.

p-Elements of group VIII Group VIII p-elements include helium He, neon Ne, argon Ar, krypton Kr, xenon Xe and radon Rh, which constitute the main subgroup. The atoms of these elements have complete outer electron layers, so the electronic configuration of the valence sublevels of their atoms in the ground state has the form 1s 2 (He) and ns 2 np 6 (other elements). Due to the very high stability of electronic configurations, they are generally characterized by high ionization energies and chemical inertness, which is why they are called noble (inert) gases. In the free state, they exist in the form of atoms (monatomic molecules). Helium (1s 2), neon (2s 2 2p 6) and argon (3s 2 3p 6) atoms have a particularly stable electronic structure, so valence-type compounds are unknown to them.

Krypton (4s 2 4p 6), xenon (5s 2 5p 6) and radon (6s 2 6p 6) differ from the previous noble gases in larger atomic sizes and, accordingly, lower ionization energies. They are able to form compounds that often have low resistance.

concept transition element commonly used to refer to any element with valence d or f electrons. These elements occupy a transitional position in the periodic table between the electropositive s-elements and the electronegative p-elements.

d-Elements are called the main transition elements. Their atoms are characterized by internal building up of d-subshells. The fact is that the s-orbital of their outer shell is usually filled already before the filling of the d-orbitals in the previous electron shell begins. This means that each new electron added to the electron shell of the next d-element, in accordance with the principle of filling, does not fall on the outer shell, but on the inner subshell that precedes it. The chemical properties of these elements are determined by the participation of electrons in the reactions of both of these shells.

d-Elements form three transition series - in the 4th, 5th and 6th periods, respectively. The first transitional series includes 10 elements, from scandium to zinc. It is characterized by internal building of 3d-orbitals. The 4s orbital fills up earlier than the 3d orbital, because it has less energy (Klechkovsky's rule).

However, two anomalies should be noted. Chromium and copper have only one electron each in their 4s orbitals. This is because half-filled or fully filled subshells are more stable than partially filled subshells.

In the chromium atom, each of the five 3d orbitals that form the 3d subshell has one electron. Such a subshell is half-filled. In the copper atom, each of the five 3d orbitals has a pair of electrons. A similar anomaly is observed in silver.

All d-elements are metals.

Electronic configurations of the elements of the fourth period from scandium to zinc:

Chromium

Chromium is in the 4th period, in the VI group, in the secondary subgroup. It is a medium activity metal. In its compounds, chromium exhibits oxidation states +2, +3 and +6. CrO is a typical basic oxide, Cr 2 O 3 is an amphoteric oxide, CrO 3 is a typical acid oxide with the properties of a strong oxidizing agent, i.e., an increase in the oxidation state is accompanied by an increase in acidic properties.

Iron

Iron is in the 4th period, in the VIII group, in the secondary subgroup. Iron is a metal of medium activity, in its compounds it exhibits the most characteristic oxidation states +2 and +3. Iron compounds are also known, in which it exhibits an oxidation state of +6, which are strong oxidizing agents. FeO exhibits basic, and Fe 2 O 3 - amphoteric with a predominance of basic properties.

Copper

Copper is in the 4th period, in group I, in a secondary subgroup. Its most stable oxidation states are +2 and +1. In a series of voltages of metals, copper is after hydrogen, its chemical activity is not very high. Copper oxides: Cu2O CuO. The latter and copper hydroxide Cu(OH)2 exhibit amphoteric properties with a predominance of basic ones.

Zinc

Zinc is in the 4th period, in the II-group, in the secondary subgroup. Zinc belongs to the metals of medium activity, in its compounds it exhibits a single oxidation state +2. Zinc oxide and hydroxide are amphoteric.

Elements in Mendeleev's periodic system are divided into s-, p-, d-elements. This subdivision is carried out on the basis of how many levels the electron shell of the element atom has and what level the filling of the shell with electrons ends with.

TO s-elements refer elements IA-groups - alkali metals. Electronic formula of the valence shell of alkali metal atoms ns1. The stable oxidation state is +1. Elements IA groups have similar properties due to the similar structure of the electron shell. With an increase in the radius in the Li-Fr group, the bond of the valence electron with the nucleus weakens and the ionization energy decreases. Atoms of alkaline elements easily donate their valence electron, which characterizes them as strong reducing agents.

Restorative properties are enhanced with increasing serial number.

TO p-elements include 30 items IIIA-VIIIA-groups periodic system; p-elements are located in the second and third small periods, as well as in the fourth to sixth large periods. Elements IIIA-groups have one electron in the p orbital. IN IVA-VIIIA-groups the filling of the p-sublevel up to 6 electrons is observed. General electronic formula of p-elements ns2np6. In periods with an increase in the nuclear charge, the atomic radii and ionic radii of p-elements decrease, the ionization energy and electron affinity increase, electronegativity increases, the oxidative activity of compounds and the non-metallic properties of elements increase. In groups, the radii of atoms increase. From 2p elements to 6p elements, the ionization energy decreases. The metallic properties of the p-element in the group increase with increasing serial number.

TO d-elements includes 32 elements of the periodic system IV–VII big periods. IN IIIB-group the atoms have the first electron in the d-orbital, in subsequent B-groups the d-sublevel is filled up to 10 electrons. General formula of the outer electron shell (n-1)dansb, where a=1?10, b=1?2. With an increase in the serial number, the properties of d-elements change insignificantly. For d-elements, the atomic radius slowly increases, and they also have a variable valence associated with the incompleteness of the pre-external d-electron sublevel. In the lower oxidation states, d-elements exhibit metallic properties; with an increase in the serial number in groups B, they decrease. In solutions, d-elements with the highest oxidation state exhibit acidic and oxidizing properties, and vice versa at lower oxidation states. Elements with an intermediate oxidation state exhibit amphoteric properties.

8. Covalent bond. Valence bond method

A chemical bond carried out by shared electron pairs arising in the shells of the bonded atoms having antiparallel spins is called atomic or covalent bond. The covalent bond is two-electron and two-center (holds nuclei). It is formed by atoms of one type - covalent non-polar– a new electron pair, which has arisen from two unpaired electrons, becomes common for two chlorine atoms; and atoms of different types, similar in chemical nature - covalent polar. Elements with greater electronegativity (Cl) will pull shared electrons away from elements with less electronegativity (H). Atoms with unpaired electrons that have parallel spins repel each other - no chemical bond occurs. The way a covalent bond is formed is called exchange mechanism.

Properties of a covalent bond. Link length - internuclear distance. The shorter this distance, the stronger the chemical bond. Bond energy - the amount of energy required to break the bond. The magnitude of the bond multiplicity is directly proportional to the bond energy and inversely proportional to the bond length. Direction of communication - a certain arrangement of electron clouds in a molecule. Saturability- the ability of an atom to form a certain number of covalent bonds. A chemical bond formed by the overlapping of electron clouds along an axis connecting the centers of atoms is called ?-connection. The bond formed by the overlapping of electron clouds perpendicular to the axis connecting the centers of atoms is called ?-bond. The spatial orientation of a covalent bond is characterized by the angles between the bonds. These angles are called valence angles. Hybridization - the process of rearrangement of electron clouds unequal in form and energy, leading to the formation of hybrid clouds identical in the same parameters. Valence is the number of chemical bonds (covalent ), through which an atom is connected to others. The electrons involved in the formation of chemical bonds are called valence. The number of bonds between atoms is equal to the number of its unpaired electrons involved in the formation of common electron pairs, so the valence does not take into account polarity and has no sign. In compounds in which there is no covalent bond, oxidation state - conditional charge of an atom, based on the assumption that it consists of positively or negatively charged ions. For most inorganic compounds, the concept of oxidation state is applicable.