The OXIDATION STATE is the charge that an atom in a molecule or ion could have if all its bonds with other atoms were broken, and the common electron pairs left with more electronegative elements.
In which of the compounds does oxygen exhibit a positive oxidation state: H2O; H2O2; CO2; OF2?
OF2. this compound, oxygen has an oxidation state of + 2
Which of the substances is only a reducing agent: Fe; SO3; Cl2; HNO3?
sulfur oxide (IV) - SO 2
What element in the III period of the Periodic system of D.I. Mendeleev, being in the free state, is the strongest oxidizing agent: Na; Al; S; Cl2?
Cl chlorine
V-part
What classes of inorganic compounds do the following substances belong to: HF, PbO2, Hg2SO4, Ni(OH)2, FeS, Na2CO3?
Complex substances. oxides
Make formulas: a) acidic potassium salts of phosphoric acid; b) basic zinc salt of carbonic acid H2CO3.
What substances are obtained by the interaction of: a) acids with a salt; b) acids with a base; c) salt with salt; d) bases with salt? Give examples of reactions.
A) metal oxides, metal salts.
B) salts (only in solution)
D) a new salt, an insoluble base and hydrogen are formed
Which of the following substances will react with hydrochloric acid: N2O5, Zn(OH)2, CaO, AgNO3, H3PO4, H2SO4? Make equations of possible reactions.
Zn(OH)2 + 2 HCl = ZnCl + H2O
CaO + 2 HCl = CaCl2 + H2O
Indicate what type of oxide copper oxide belongs to and prove it with the help of chemical reactions.
metal oxide.
Copper oxide (II) CuO - black crystals, crystallize in a monoclinic system, density 6.51 g / cm3, melting point 1447 ° C (under oxygen pressure). When heated to 1100°C, it decomposes to form copper (I) oxide:
4CuO = 2Cu2O + O2.
It does not dissolve in water and does not react with it. It has weakly expressed amphoteric properties with a predominance of basic ones.
In aqueous solutions of ammonia, it forms tetraammine copper (II) hydroxide:
CuO + 4NH3 + H2O = (OH)2.
Easily reacts with dilute acids to form salt and water:
CuO + H2SO4 = CuSO4 + H2O.
When fused with alkalis, it forms cuprates:
CuO + 2KOH = K2CuO2 + H2O.
Reduced by hydrogen, carbon monoxide and active metals to metallic copper:
CuO + H2 = Cu + H2O;
CuO + CO = Cu + CO2;
CuO + Mg = Cu + MgO.
It is obtained by calcining copper (II) hydroxide at 200 ° C:
Cu(OH)2 = CuO + H2O Obtaining oxide and hydroxide of copper (II)
or during the oxidation of metallic copper in air at 400–500°С:
2Cu + O2 = 2CuO.
6. Finish the reaction equations:
Mg(OH)2 + H2SO4 = MgSO4+2H2O
Mg(OH)2^- +2H^+ + SO4^2-=Mg^2+ + SO4^2- +2H2O
Mg(OH)2^- +2H^+ = Mg^2+ +2H2O^-
NaOH + H3PO4 \u003d NaH2PO4 + H2O FE \u003d 1
H3PO4 + 2NaOH \u003d Na2HPO4 + 2H2O FE \u003d 1/2
H3PO4 + 3NaOH \u003d Na3PO4 + 3H2O FE \u003d 1/3
in the first case, 1 mol of phosphoric acid hm .. . equivalent to 1 proton... so the equivalence factor is 1
percentage concentration - the mass of a substance in grams contained in 100 grams of a solution. if 100 g of solution contains 5 g of salt, how much is needed for 500 g?
titer is the mass of a substance in grams contained in 1 ml of a solution. 0.3 g is enough for 300 ml.
Ca (OH) 2 + H2CO3 \u003d CaO + H2O 2 / characteristic reaction - neutralization reaction Ca / OH / 2 + H2CO3 \u003d CaCO3 + H2O 3 / react with acid oxides Ca / OH / 2 + CO2 \u003d CaCO3 + H2O 4 / with acidic salts Ca / OH / 2 + 2KHCO3 \u003d K2CO3 + CaCO3 + 2H2O 5 / alkalis enter into an exchange reaction with salts. if in this case a precipitate is formed 2NaOH + CuCl2 = 2NaCl + Cu / OH / 2 / precipitate / 6 / alkali solutions react with non-metals, as well as with aluminum or zinc. OVR.
Name three ways to obtain salts. Support your answer with the reaction equations
A) Neutralization reaction.. After evaporation of water, a crystalline salt is obtained. For example:
B) Reaction of bases with acidic oxides(see paragraph 8.2). This is also a variant of the neutralization reaction:
IN) Reaction of acids with salts. This method is suitable, for example, if an insoluble salt is formed that precipitates:
Which of the following substances can react with each other: NaOH, H3PO4, Al(OH)3, SO3, H2O, CaO? Support your answer with the reaction equations
2 NaOH + H3PO4 = Na2HPO4 + 2H2O
CaO + H2O = Ca(OH)2
Al(OH)3 + NaOH = Na(Al(OH)4) or NaAlO2 + H2O
SO3 + H2O = H2SO4
VI part
The nucleus of an atom (protons, neutrons).
An atom is the smallest particle of a chemical element that retains all of its Chemical properties. An atom consists of a positively charged nucleus and negatively charged electrons. The charge of the nucleus of any chemical element is equal to the product of Z by e, where Z is the serial number of this element in the periodic system of chemical elements, e is the value of the elementary electric charge.
Protons- stable elementary particles having a unit positive electric charge and a mass 1836 times greater than the mass of an electron. The proton is the nucleus of the lightest element, hydrogen. The number of protons in the nucleus is Z. Neutron- a neutral (not having an electric charge) elementary particle with a mass very close to the mass of a proton. Since the mass of the nucleus is made up of the mass of protons and neutrons, the number of neutrons in the nucleus of an atom is A - Z, where A is the mass number of a given isotope (see Periodic system of chemical elements). The proton and neutron that make up the nucleus are called nucleons. In the nucleus, nucleons are bound by special nuclear forces.
Electrons
Electron- the smallest particle of a substance with a negative electric charge e=1.6·10 -19 coulombs, taken as an elementary electric charge. Electrons, rotating around the nucleus, are located on the electron shells K, L, M, etc. K is the shell closest to the nucleus. The size of an atom is determined by the size of its electron shell.
isotopes
Isotope - an atom of the same chemical element, the nucleus of which has the same number of protons (positively charged particles), but a different number of neutrons, and the element itself has the same atomic number as the main element. Because of this, isotopes have different atomic masses.
When bonds are formed with less electronegative atoms (for fluorine, these are all elements, for chlorine, everything except fluorine and oxygen), the valency of all halogens is equal. The oxidation state is -1 and the charge of the ion is 1-. Positive oxidation states are not possible for fluorine. Chlorine, on the other hand, exhibits various positive oxidation states up to +7 (group number). Connection examples are given in the Reference section.
In most compounds, chlorine, as a strongly electronegative element (EO = 3.0), acts in a negative oxidation state of -1. In compounds with more electronegative fluorine, oxygen and nitrogen, it exhibits positive oxidation states. Compounds of chlorine with oxygen are especially diverse, in which the oxidation states of chlorine are +1, -f3, +5 and +7, as well as +4 and Ch-6.
Compared to chlorine, fluorine F is much more active. It reacts with almost all chemical elements, with alkali and alkaline earth metals, even in the cold. Some metals (Mg, Al, Zn, Fe, Cu, Ni) are resistant to fluorine in the cold due to the formation of a fluoride film. Fluorine is the strongest oxidizing agent of all known elements. It is the only halogen incapable of exhibiting positive oxidation states. When heated, fluorine reacts with all metals, including gold and platinum. It forms a number of compounds with oxygen, and these are the only compounds in which oxygen is electropositive (for example, oxygen difluoride OFa). Unlike oxides, these compounds are called oxygen fluorides.
The elements of the oxygen subgroup differ significantly from oxygen in properties. Their main difference lies in the ability to show positive oxidation states, up to
The differences between halogens are most noticeable in compounds where they exhibit positive oxidation states. These are mainly compounds of halogens with the most electronegative elements - fluorine and oxygen, which
The oxygen atom has the electronic configuration [He]25 2р. Since this element is second only to fluorine in its electronegativity, it almost always has a negative oxidation state in compounds. The only compounds where oxygen has a positive oxidation state are the fluorine-containing compounds Op2 and Op.
In 1927, an oxygen compound of fluorine was indirectly obtained, in which oxygen has a positive oxidation state equal to two
Since the nitrogen atoms in ammonia attract electrons more strongly than in elemental nitrogen, they are said to have a negative oxidation state. In nitrogen dioxide, where nitrogen atoms attract electrons less strongly than in elemental nitrogen, it has a positive oxidation state. In elemental nitrogen or elemental oxygen, each atom has an oxidation state of zero. (Oxidation state zero is attributed to all elements in the uncombined state.) Oxidation state is a useful concept for understanding redox reactions.
Chlorine forms a whole series of oxyanions ClO, ClO, ClO3, and ClOg, in which it exhibits a successive series of positive oxidation states. The chloride ion, C1, has the electronic structure of the noble gas Ar, with four pairs of valence electrons. The above four chlorine oxyanions can be thought of as reaction products of a chloride ion, CH, as a Lewis base with one, two, three, or four oxygen atoms, each of which has electron acceptor properties, i.e. lewis acid
The chemical properties of sulfur, selenium and tellurium differ in many respects from those of oxygen. One of the most important differences is that these elements have positive oxidation states up to -1-6, which are found, for example,
The electronic configuration ns np enables the elements of this group to exhibit the oxidation states -I, +11, +IV and +VI. Since only two electrons are missing before the formation of the inert gas configuration, the -II oxidation state arises very easily. This is especially true for the light elements of the group.
Indeed, oxygen differs from all elements of the group in the ease with which its atom acquires two electrons, forming a doubly charged negative ion. With the exception of the unusual negative oxidation states of oxygen in peroxides (-1), superoxides (-Va) and ozonides (7h), compounds in which there are oxygen-oxygen bonds, as well as states + 1 and - + II in compounds O. Fa and ORz oxygen in all compounds has an oxidation state of -I. For the remaining elements of the group, the negative oxidation state becomes gradually less stable, and the positive ones become more stable. Heavy elements are dominated by lower positive oxidation states.
In accordance with the nature of the element in a positive oxidation state, the nature of the oxides in the periods and groups of the periodic system naturally changes. In periods, the negative effective charge on oxygen atoms decreases and a gradual transition from basic through amphoteric oxides to acidic ones occurs, for example
Nal, Mgb, AIF3, ZrBf4. When determining the oxidation state of elements in compounds with polar covalent bonds, the values of their electronegativity are compared (see 1.6). Since, during the formation of a chemical bond, electrons are shifted to atoms of more electronegative elements, the latter have a negative oxidation state in compounds , in compounds always has a constant negative oxidation state -1.
I oxygen, which also has a high electronegativity value, is characterized by a negative oxidation state, usually -2, in peroxides -1. The exception is compound OF2, in which the oxidation state of oxygen is 4-2. Alkaline and alkaline earth elements, which are characterized by a relatively low electronegativity, always have a positive oxidation state, equal to +1 and +2, respectively. Hydrogen exhibits a constant oxidation state (+ 1) in most compounds, for example
In terms of electronegativity, oxygen is second only to fluorine. Oxygen compounds with fluorine are unique, since only in these compounds oxygen has a positive oxidation state.
Derivatives of a positive oxidation state of oxygen are the strongest energy-intensive oxidizing agents capable of releasing the chemical energy stored in them under certain conditions. They can be used as effective propellant oxidizers.
And they belong to non-metals, the indicated state is the most common for them. However, the elements of group 6A, with the exception of oxygen, are often in states with a positive oxidation state up to + 6, which corresponds to the socialization of all six valence electrons with atoms of more electronegative elements.
All elements of this subgroup, except for polonium, are non-metals. In their compounds, they exhibit both negative and positive oxidation states. In compounds with metals and hydrogen, their oxidation state is usually -2. In compounds with non-metals, for example with oxygen, it can have a value of +4 or -) -6. The exception is oxygen itself. In terms of electronegativity, it is second only to fluorine, therefore, only in combination with this element (OR) its oxidation state is positive (-1-2). In compounds with all other elements, the oxidation state of oxygen is negative and is usually -2. In hydrogen peroxide and its derivatives, it is -1.
Nitrogen is inferior in electronegativity only to oxygen and fluorine. Therefore, it exhibits positive oxidation states only in compounds with these two elements. In oxides and oxyanions, the oxidation state of nitrogen takes on values from + 1 to -b 5.
In compounds with more electronegative elements, p-elements of group VI have a positive oxidation state. For them (except oxygen), the most characteristic oxidation states are -2, +4, -4-6, which corresponds to a gradual increase in the number unpaired electrons when an atom of an element is excited.
Especially well known are complex anions with oxygen ligands - oxo complexes. They are formed by atoms of predominantly non-metallic elements in positive oxidation states (metal - only in high oxidation states). Oxo complexes are obtained by the interaction of covalent oxides of the corresponding elements with a negatively polarized oxygen atom of basic oxides or water, for example
oxides and hydroxides. Oxides and hydroxides of p-elements can be considered as compounds with the highest positive oxidation state, p-elements with oxygen
O, CJUg, CbO), in which chlorine exhibits a positive oxidation state. Nitrogen at high temperatures directly combines with oxygen and, therefore, exhibits reducing properties.
In compounds with oxygen, elements can show the highest positive oxidation state, equal to the group number. Oxides of elements, depending on their position in the periodic system and on the degree of oxidation of the element, can exhibit basic or acidic properties.
In addition, these elements are also capable of exhibiting positive oxidation states up to +6, with the exception of oxygen (only up to + 2). Elements of the oxygen subgroup are non-metals.
The most common oxidizing agents are halogens, oxygen, and oxyanions such as MPO4, Cr3O, and NO, in which the central atom has a high positive oxidation state. Sometimes as oxidizers
OgRg and Oorg compounds are strong oxidizing agents, since oxygen in them is in a positive oxidation state - -1 and +2, and therefore, having a large energy reserve (high electron affinity), they will strongly attract electrons due to the desire of oxygen to go into the most stable states for him.
Ionized atoms of non-metals in a positive oxidation state and metal ions in a high oxidation state with oxygen form neutral molecules of oxides CO, CO2, NO, N02, 302, SnO2, MnOa complex oxygen-containing ions N0, P04, 3O ", Cr0, MnOg, etc. .
The high electrochemical level of atoms of these elements corresponds to the formula pa pr Oxygen is the second most electronegative element (after the most negative fluorine), it can be assigned a stable oxidation state in compounds equal to (-I) in oxygen fluorides its oxidation state is positive. The remaining elements of the VIA group exhibit oxidation states (-I), (+ IV) and (Ch VI) in their compounds, and the oxidation state is stable for sulfur (+ VI), and for the remaining elements (4-IV). By electronegativity
When O2 interacts with the strongest oxidizing agent P1Pv, a substance O2[P1Pb] is formed, in which the molecular ion Og is the cation. Compounds in which oxygen has a positive oxidation state are the strongest energy-intensive oxidizing agents capable of releasing stored chemical energy under certain conditions. They can be used as effective propellant oxidizers.
However, the ability to attach electrons is much less pronounced in them than in the corresponding elements of groups VI and VII. With oxygen, they form oxides of the RjOj type, showing the highest positive oxidation state, equal to + 5.
Bromine and iodine exhibit positive oxidation states in their compounds with oxygen and with more electronegative halogens. Well studied are such oxygen-containing acids (and their salts) of these elements as HOHg (bromous, salts are hypobromites) and HOI (iodine, salts are hypoiodites) HBrO3 (bromous, salts are bromates) and NHS (iodine, salts are iodates) , as well as NbYub (ortho-iodic, salts - ortho-periodates).
A chemical element in a compound, calculated from the assumption that all bonds are ionic.
The oxidation states can have a positive, negative or zero value, therefore the algebraic sum of the oxidation states of elements in a molecule, taking into account the number of their atoms, is 0, and in an ion - the charge of the ion.
1. The oxidation states of metals in compounds are always positive.
2. The highest oxidation state corresponds to the group number of the periodic system where this element is located (the exception is: Au+3(I group), Cu+2(II), from group VIII, the oxidation state +8 can only be in osmium Os and ruthenium Ru.
3. The oxidation states of non-metals depend on which atom it is connected to:
- if with a metal atom, then the oxidation state is negative;
- if with a non-metal atom, then the oxidation state can be both positive and negative. It depends on the electronegativity of the atoms of the elements.
4. The highest negative oxidation state of non-metals can be determined by subtracting from 8 the number of the group in which this element is located, i.e. the highest positive oxidation state is equal to the number of electrons on the outer layer, which corresponds to the group number.
5. The oxidation states of simple substances are 0, regardless of whether it is a metal or a non-metal.
Elements with constant oxidation states.
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Element |
Characteristic oxidation state |
Exceptions |
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Metal hydrides: LIH-1 |
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oxidation state called the conditional charge of the particle under the assumption that the bond is completely broken (has an ionic character). H- Cl = H + + Cl - , The bond in hydrochloric acid is covalent polar. The electron pair is more biased towards the atom Cl - , because it is more electronegative whole element. How to determine the degree of oxidation?Electronegativity is the ability of atoms to attract electrons from other elements. The oxidation state is indicated above the element: Br 2 0 , Na 0 , O +2 F 2 -1 ,K + Cl - etc. It can be negative and positive. The oxidation state of a simple substance (unbound, free state) is zero. The oxidation state of oxygen in most compounds is -2 (the exception is peroxides H 2 O 2, where it is -1 and compounds with fluorine - O +2 F 2 -1 , O 2 +1 F 2 -1 ). - Oxidation state a simple monatomic ion is equal to its charge: Na + , Ca +2 . Hydrogen in its compounds has an oxidation state of +1 (exceptions are hydrides - Na + H - and type connections C +4 H 4 -1 ). In metal-non-metal bonds, the atom that has the highest electronegativity has a negative oxidation state (electronegativity data are given on the Pauling scale): H + F - , Cu + Br - , Ca +2 (NO 3 ) - etc. Rules for determining the degree of oxidation in chemical compounds.Let's take a connection KMnO 4 , it is necessary to determine the oxidation state of the manganese atom. Reasoning:
K+MnXO 4 -2 Let X- unknown to us the degree of oxidation of manganese. The number of potassium atoms is 1, manganese - 1, oxygen - 4. It is proved that the molecule as a whole is electrically neutral, so its total charge must be equal to zero. 1*(+1) + 1*(X) + 4(-2) = 0, X = +7, Hence, the oxidation state of manganese in potassium permanganate = +7. Let's take another example of an oxide Fe2O3. It is necessary to determine the oxidation state of the iron atom. Reasoning:
2*(X) + 3*(-2) = 0, Conclusion: the oxidation state of iron in this oxide is +3. Examples. Determine the oxidation states of all atoms in the molecule. 1. K2Cr2O7. Oxidation state K+1, oxygen O -2. Given indexes: O=(-2)×7=(-14), K=(+1)×2=(+2). Because the algebraic sum of the oxidation states of elements in a molecule, taking into account the number of their atoms, is 0, then the number of positive oxidation states is equal to the number of negative ones. Oxidation states K+O=(-14)+(+2)=(-12). It follows from this that the number of positive powers of the chromium atom is 12, but there are 2 atoms in the molecule, which means that there are (+12):2=(+6) per atom. Answer: K 2 + Cr 2 +6 O 7 -2. 2.(AsO 4) 3-. In this case, the sum of the oxidation states will no longer be equal to zero, but to the charge of the ion, i.e. - 3. Let's make an equation: x+4×(- 2)= - 3 . Answer: (As +5 O 4 -2) 3-. |
DEFINITION
Oxygen is the eighth element in the Periodic Table. It is located in the second period of the VI group A of the subgroup. Designation - O.
Natural oxygen consists of three stable isotopes 16O (99.76%), 17O (0.04%) and 18O (0.2%).
The most stable diatomic oxygen molecule is O 2 . It is paramagnetic and weakly polarized. The melting points (-218.9 o C) and boiling points (-183 o C) of oxygen are very low. Oxygen is poorly soluble in water. At normal conditions Oxygen is a colorless and odorless gas.
Liquid and solid oxygen is attracted by a magnet, because. its molecules are paramagnetic. Solid oxygen is blue, and liquid oxygen is blue. Coloring is due to the mutual influence of molecules.
Oxygen exists in the form of two allotropic modifications - oxygen O 2 and ozone O 3.
The oxidation state of oxygen in compounds
Oxygen forms diatomic molecules of composition O 2 due to the induction of covalent non-polar bonds, and, as is known, in compounds with non-polar bonds, the oxidation state of the elements is zero.
Oxygen is characterized by a rather high electronegativity value, therefore, most often it exhibits a negative oxidation state equal to (-2) (Na 2 O -2, K 2 O -2, CuO -2, PbO -2, Al 2 O -2 3, Fe 2 O -2 3, NO -2 2, P 2 O -2 5, CrO -2 3, Mn 2 O -2 7).
In peroxide-type compounds, oxygen exhibits an oxidation state (-1) (H 2 O -1 2).
In the OF 2 compound, oxygen exhibits a positive oxidation state equal to (+2) , since fluorine is the most electronegative element and its oxidation state is always (-1).
As a derivative in which oxygen exhibits an oxidation state (+4) , we can consider the allotropic modification of oxygen - ozone O 3 (O +4 O 2).
Examples of problem solving
EXAMPLE 1
Redox processes are of great importance for living and inanimate nature. For example, the combustion process can be attributed to the OVR with the participation of atmospheric oxygen. In this redox reaction, it exhibits its non-metallic properties.
Also examples of OVR are digestive, respiratory processes, photosynthesis.
Classification
Depending on whether there is a change in the value of the oxidation state of the elements of the initial substance and the product of the reaction, it is customary to subdivide all chemical transformations into two groups:
- redox;
- no change in oxidation states.
Examples of the second group are ionic processes occurring between solutions of substances.
Oxidation-reduction reactions are processes that are associated with a change in the oxidation state of the atoms that make up the original compounds.
What is oxidation state
This is the conditional charge acquired by an atom in a molecule when the electron pairs of chemical bonds are shifted to a more electronegative atom.
For example, in the sodium fluoride (NaF) molecule, fluorine exhibits the maximum electronegativity, so its oxidation state is a negative value. The sodium in this molecule will be a positive ion. The sum of the oxidation states in a molecule is zero.
Definition options
What kind of ion is oxygen? Positive oxidation states are uncharacteristic for it, but this does not mean that this element does not show them in certain chemical interactions.
The very concept of the degree of oxidation has a formal character, it is not associated with the effective (real) charge of the atom. They are useful for classifying chemical substances, as well as when recording ongoing processes.
Definition rules
For non-metals, the lowest and highest oxidation states are distinguished. If eight is subtracted from the group number to determine the first indicator, then the second value basically coincides with the number of the group in which this is located. chemical element. For example, in compounds, it is usually -2. Such compounds are called oxides. For example, such substances include carbon dioxide (carbon dioxide), the formula of which is CO 2.
Non-metals often show the maximum oxidation state in acids and salts. For example, in perchloric acid HClO 4, the halogen has a valence of VII (+7).
Peroxides
The oxidation state of the oxygen atom in compounds is usually -2, with the exception of peroxides. They are considered oxygen compounds, which contain an incompletely reduced ion in the form of O 2 2-, O 4 2-, O 2 -.
Peroxide compounds are divided into two groups: simple and complex. Simple compounds are those in which the peroxide group is connected to the metal atom or ion by an atomic or ionic chemical bond. Such substances are formed by alkali and alkaline earth metals (except lithium and beryllium). With an increase in the electronegativity of the metal within the subgroup, a transition from the ionic type of bond to the covalent structure is observed.
In addition to peroxides of the Me 2 O 2 type, representatives of the first group (main subgroup) also have peroxides in the form of Me 2 O 3 and Me 2 O 4 .
If oxygen exhibits a positive oxidation state with fluorine, in combination with metals (in peroxides) this indicator is -1.
Complex peroxo compounds are substances where this group acts as ligands. Similar substances are formed by elements of the third group (main subgroup), as well as subsequent groups.
Classification of complex peroxo groups
There are five groups of such complex compounds. The first is peroxoacids having the general form [Ep(O 2 2-) x L y ] z- . In this case, peroxide ions enter the complex ion or act as a monodentate (E-O-O-), bridging (E-O-O-E) ligand, forming a multinuclear complex.
If oxygen exhibits a positive oxidation state with fluorine, in combination with alkali and alkaline earth metals it is a typical non-metal (-1).
An example of such a substance is Caro's acid (peroxomonomeric acid) of the form H 2 SO 5 . The ligand peroxide group in such complexes acts as a bridge between non-metal atoms, for example, in peroxodisulfuric acid of the form H 2 S 2 O 8 - a white crystalline substance with a low melting point.
The second group of complexes is created by substances in which the peroxo group is part of a complex ion or molecule.
They are represented by the formula [E n (O 2) x L y] z.
The remaining three groups are peroxides, which contain water of crystallization, for example, Na 2 O 2 × 8H 2 O, or hydrogen peroxide of crystallization.
As typical properties of all peroxide substances, we single out their interaction with acid solutions, the release of active oxygen during thermal decomposition.
Chlorates, nitrates, permanganates, perchlorates can act as a source of oxygen.
oxygen difluoride
When does oxygen show a positive oxidation state? In conjunction with more electronegative oxygen) OF 2. It is +2. This compound was first obtained by Paul Lebo at the beginning of the twentieth century, studied a little later by Ruff.
Oxygen exhibits a positive oxidation state when combined with fluorine. Its electronegativity is 4, so the electron density in the molecule shifts towards the fluorine atom.
Properties of oxygen fluoride
This compound is in a liquid state of aggregation, it is infinitely miscible with liquid oxygen, fluorine, and ozone. Solubility in cold water minimum.
How is a positive oxidation state explained? Big Encyclopedia oil explains that it is possible to determine the highest + (positive) oxidation state by the group number in the periodic table. This value is determined largest number electrons that a neutral atom can donate during complete oxidation.
Oxygen fluoride is obtained by the alkaline method, which involves passing fluorine gas through an aqueous solution of alkali.
In this, in addition to oxygen fluoride, ozone and hydrogen peroxide are also formed.
An alternative option for obtaining oxygen fluoride is to carry out the electrolysis of a solution of hydrofluoric acid. Partially, this compound is also formed during combustion in an atmosphere of water fluorine.
The process proceeds according to a radical mechanism. First, the initiation of free radicals is carried out, accompanied by the formation of an oxygen biradical. The next step is the dominant process.
Oxygen difluoride exhibits bright oxidizing properties. Its strength can be compared with free fluorine, and in terms of the mechanism of the oxidative process, it can be compared with ozone. The reaction needs a high activation energy, since the formation of atomic oxygen occurs at the first stage.
The thermal decomposition of this oxide, in which oxygen is characterized by a positive oxidation state, is a monomolecular reaction starting at temperatures above 200 °C.
Distinctive characteristics
When oxygen fluoride enters hot water hydrolysis proceeds, the products of which will be ordinary molecular oxygen, as well as hydrogen fluoride.
The process is significantly accelerated in an alkaline environment. A mixture of water and oxygen difluoride vapor is explosive.
This compound reacts intensively with metallic mercury, and on noble metals (gold, platinum) it forms only a thin fluoride film. This property explains the possibility of using these metals at ordinary temperature for contact with oxygen fluoride.
In the case of an increase in temperature, the oxidation of metals occurs. Magnesium and aluminum are considered the most suitable metals for working with this fluorine compound.
slightly change their original appearance under the influence of oxygen fluoride stainless steels, copper alloys.
The high activation energy of the decomposition of this oxygen compound with fluorine allows it to be safely mixed with various hydrocarbons, carbon monoxide, and explains the possibility of using oxygen fluoride as an excellent rocket fuel oxidizer.
Conclusion
Chemists carried out a number of experiments that confirmed the expediency of using this compound in gas-dynamic laser installations.
Issues related to the determination of the oxidation states of oxygen and other non-metals are included in the school chemistry course.
Such skills are important because they allow high school students to cope with the tasks offered in the tests of the unified state exam.
(repetition)
II. Oxidation state (new material)
Oxidation state- this is the conditional charge that the atom receives as a result of the complete return (acceptance) of electrons, based on the condition that all bonds in the compound are ionic.
Consider the structure of fluorine and sodium atoms:
F +9)2)7
Na+11)2)8)1
What can be said about completion? external level fluorine and sodium atoms?
Which atom is easier to accept and which is easier to give valence electrons for the purpose of completing the outer layer?
Do both atoms have an incomplete outer level?
It is easier for the sodium atom to donate electrons, for fluorine to accept electrons before the completion of the external level.
F 0 + 1ē → F -1 (a neutral atom accepts one negative electron and acquires an oxidation state of "-1", turning into negatively charged ion - anion )
Na 0 – 1ē → Na +1 (a neutral atom donates one negative electron and acquires an oxidation state of "+1", turning into positively charged ion - cation )
How to determine the oxidation state of an atom in PSCE D.I. Mendeleev?
Definition rules oxidation states of an atom in PSCE D.I. Mendeleev:
1. Hydrogen usually exhibits an oxidation state (CO) +1 (exception, compounds with metals (hydrides) - hydrogen has CO equal to (-1) Me + n H n -1)
2. Oxygen usually exhibits CO -2 (exceptions: O +2 F 2, H 2 O 2 -1 - hydrogen peroxide)
3. Metals only show + n positive CO
4. Fluorine always shows CO equal -1 (F-1)
5. For elements main subgroups:
Higher CO (+) = group number N groups
Inferior CO (-) = N groups – 8
Rules for determining the oxidation state of an atom in a compound:
I. Oxidation state free atoms and atoms in molecules simple substances is equal to zero - Na 0 , P 4 0 , O 2 0
II. IN complex substance the algebraic sum of CO of all atoms, taking into account their indices, is equal to zero = 0 , and in complex ion its charge.
For example, H +1 N +5 O 3 -2 : (+1)*1+(+5)*1+(-2)*3 = 0
2- : (+6)*1+(-2)*4 = -2
Exercise 1 - determine the oxidation states of all atoms in the formula of sulfuric acid H 2 SO 4?
1. Let's put down the known oxidation states of hydrogen and oxygen, and take the CO of sulfur as "x"
H +1 S x O 4 -2
(+1)*1+(x)*1+(-2)*4=0
X \u003d 6 or (+6), therefore, sulfur has C O +6, i.e. S+6
Task 2 - determine the oxidation states of all atoms in the formula of phosphoric acid H 3 PO 4?
1. Let's put down the known oxidation states of hydrogen and oxygen, and take the CO of phosphorus as "x"
H 3 +1 P x O 4 -2
2. Compose and solve the equation, according to the rule (II):
(+1)*3+(x)*1+(-2)*4=0
X \u003d 5 or (+5), therefore, phosphorus has C O +5, i.e. P+5
Task 3 - determine the oxidation states of all atoms in the formula of the ammonium ion (NH 4) + ?
1. Let's put down the known oxidation state of hydrogen, and take the CO of nitrogen as "x"
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