EntranceHow to determine the positive and negative oxidation states. Inorganic chemistry
Valence and oxidation state are concepts often used in non-technical organic chemistry. In many chemical compounds, the valence value and the oxidation state of an element are the same, which is why schoolchildren and students often get confused. These concepts do have some things in common, but the differences are more significant. To understand how these two concepts differ, it is worth learning more about them.
Oxidation state information
The oxidation state is an auxiliary quantity assigned to an atom of a chemical element or group of atoms, which shows how shared pairs of electrons are distributed between interacting elements.
This is an auxiliary quantity that does not have physical meaning as such. Its essence can be easily explained with the help of examples:
Table salt molecule NaCl consists of two atoms - a chlorine atom and a sodium atom. The bond between these atoms is ionic. Sodium has 1 electron at the valence level, which means it shares one electron pair with the chlorine atom. Of these two elements, chlorine is more electronegative (has the property of mixing electron pairs towards itself), then the only common pair of electrons will shift towards it. In a compound, an element with a higher electronegativity has a negative oxidation state, while a less electronegative element has a positive oxidation state, and its value is equal to the number of shared pairs of electrons. For the NaCl molecule in question, the oxidation states of sodium and chlorine will look like this:
Chlorine, with an electron pair displaced to it, is now considered an anion, that is, an atom that has added an additional electron, and sodium is considered a cation, that is, an atom that has donated an electron. But when writing the oxidation state, the sign comes first, and the numerical value comes second, and when writing the ionic charge, it’s the other way around.
The oxidation state can be defined as the number of electrons that a positive ion lacks to reach an electrically neutral atom, or that must be taken from a negative ion in order to oxidize to an atom. In this example, it is obvious that the positive sodium ion lacks an electron due to the displacement of the electron pair, and the chlorine ion has one extra electron.
The oxidation state of a simple (pure) substance, regardless of its physical and chemical properties, is equal to zero. The O2 molecule, for example, consists of two oxygen atoms. They have the same electronegativity values, so the shared electrons do not shift to either of them. This means that the electron pair is strictly between the atoms, so the oxidation state will be zero.
For some molecules, it can be difficult to determine where the electrons go, especially if there are three or more elements. To calculate the oxidation states in such molecules, you need to use a few simple rules:
- The hydrogen atom almost always has a constant oxidation state of +1..
- For oxygen this figure is -2. The only exception to this rule is fluorine oxides
ОF 2 and О 2 F 2,
Since fluorine is the element with the highest electronegativity, it always displaces interacting electrons towards itself. According to international rules, the element with a lower electronegativity value is written first, therefore oxygen comes first in these oxides.
- If you add up all the oxidation states in a molecule, you get zero.
- Metal atoms are characterized by a positive oxidation state.
When calculating oxidation states, you need to remember that the highest oxidation state of an element is equal to the number of its group, and the minimum is the group number minus 8. For chlorine, the maximum possible value of the oxidation state is +7, because it is in the 7th group, and the minimum is 7-8 = -1. 
General information about valency
Valency is the number of covalent bonds that an element can form in different compounds.
Unlike the oxidation state, the concept of valence has a real physical meaning.
The highest valence index is equal to the group number in the periodic table. Sulfur S is located in the 6th group, that is, its maximum valency is 6. But it can also be 2 (H 2 S) or 4 (SO 2).
Almost all elements are characterized by variable valency. However, there are atoms for which this value is constant. These include alkali metals, silver, hydrogen (their valence is always 1), zinc (valency is always 2), lanthanum (valence is always 3). 
What do valency and oxidation state have in common?
- To denote both quantities, positive integers are used, which are written above the Latin designation of the element.
- The highest valency, as well as the highest oxidation state, coincides with the group number of the element.
- The oxidation state of any element in a complex compound coincides with numerical value one of the valence indicators. For example, chlorine, being in the 7th group, can have a valence of 1, 3, 4, 5, 6, or 7, which means the possible oxidation states are ±1, +3, +4, +5, +6, +7.
The main differences between these concepts
- The concept of “valence” has a physical meaning, but oxidation number is an auxiliary term that has no real physical meaning.
- The oxidation state can be zero, greater or less than zero. Valence is strictly greater than zero.
- Valency represents the number of covalent bonds, and oxidation state represents the distribution of electrons in the compound.
DEFINITION
Atom's ability to form chemical bonds called valency. A quantitative measure of valence is considered to be the number of different atoms in a molecule with which a given element forms bonds.
According to the exchange mechanism of the valence bond method, the valence of chemical elements is determined by the number of unpaired electrons contained in an atom. For s- and p-elements, these are electrons of the outer level; for d-elements, these are electrons of the outer and pre-external levels.
The values of the highest and lowest valencies of a chemical element can be determined using the Periodic Table D.I. Mendeleev. The highest valence of an element coincides with the number of the group in which it is located, and the lowest is the difference between the number 8 and the group number. For example, bromine is located in group VIIA, which means its highest valence is VII, and its lowest is I.
Paired electrons (located two at a time in atomic orbitals) upon excitation can be separated in the presence of free cells of the same level (the separation of electrons into any level is impossible). Let's look at the example of elements of groups I and II. For example, the valence of elements of the main subgroup of group I is equal to one, since at the outer level the atoms of these elements have one electron:
3 Li 1s 2 2s 1
The valence of elements of the main subgroup of group II in the ground (unexcited) state is zero, since there are no unpaired electrons at the outer energy level:
4 Be 1s 2 2 s 2
When these atoms are excited, the paired s-electrons are separated into free cells of the p-sublevel of the same level and the valence becomes equal to two (II):
Oxidation state
To characterize the state of elements in compounds, the concept of oxidation state was introduced.
DEFINITION
The number of electrons displaced from an atom of a given element or to an atom of a given element in a compound is called oxidation state.
A positive oxidation state indicates the number of electrons that are displaced from a given atom, and a negative oxidation state indicates the number of electrons that are displaced toward a given atom.
From this definition it follows that in connections with non-polar bonds the oxidation state of elements is zero. Examples of such compounds are molecules consisting of identical atoms (N 2, H 2, Cl 2).
The oxidation state of metals in the elemental state is zero, since the distribution of electron density in them is uniform.
In simple ionic compounds, the oxidation state of the elements included in them is equal to the electric charge, since during the formation of these compounds there is an almost complete transition of electrons from one atom to another: Na +1 I -1, Mg +2 Cl -1 2, Al +3 F - 1 3 , Zr +4 Br -1 4 .
When determining the oxidation state of elements in compounds with polar covalent bonds, their electronegativity values are compared. Since during the formation of a chemical bond, electrons are displaced to the atoms of more electronegative elements, the latter have a negative oxidation state in compounds.
The concept of oxidation state for most compounds is conditional, since it does not reflect the real charge of the atom. However, this concept is very widely used in chemistry.
Most elements can exhibit varying degrees of oxidation in compounds. When determining their oxidation state, they use the rule according to which the sum of the oxidation states of elements in electrically neutral molecules is equal to zero, and in complex ions - the charge of these ions. As an example, let's calculate the degree of oxidation of nitrogen in compounds of the composition KNO 2 and HNO 3. The oxidation state of hydrogen and alkali metals in compounds is (+), and the oxidation state of oxygen is (-2). Accordingly, the oxidation degree of nitrogen is equal to:
KNO 2 1+ x + 2 × (-2) = 0, x=+3.
HNO 3 1+x+ x + 3 × (-2) = 0, x=+5.
Examples of problem solving
EXAMPLE 1
| Exercise | Valence IV is characteristic of: a) Ca; b) P; c) O; d)Si? |
| Solution | In order to give the correct answer to the question posed, we will consider each of the proposed options separately. a) Calcium is a metal. It is characterized by the only possible valency value, coinciding with the group number in the Periodic Table D.I. Mendeleev, in which it is located, i.e. The valence of calcium is II. The answer is incorrect. b) Phosphorus is a non-metal. Refers to a group of chemical elements with variable valence: the highest is determined by the group number in the Periodic Table D.I. Mendeleev, in which it is located, i.e. is equal to V, and the lowest is the difference between the number 8 and the group number, i.e. equal to III. The answer is incorrect. c) Oxygen is a non-metal. It is characterized by the only possible valency value equal to II. The answer is incorrect. d) Silicon is a non-metal. It is characterized by the only possible valency value, coinciding with the group number in the Periodic Table D.I. Mendeleev, in which it is located, i.e. The valence of silicon is IV. This is the correct answer. |
| Answer | Option (d) |
EXAMPLE 2
| Exercise | What is the valency of iron in the compound that is formed when it reacts with hydrochloric acid: a)I; b) II; c) III; d) VIII? |
| Solution | Let us write the equation for the interaction of iron with hydrochloric acid: Fe + HCl = FeCl 2 + H 2. As a result of the interaction, ferric chloride is formed and hydrogen is released. To determine the valency of iron using the chemical formula, we first count the number of chlorine atoms: We calculate the total number of chlorine valence units: We determine the number of iron atoms: it is equal to 1. Then the valency of iron in its chloride will be equal to: |
| Answer | The valency of iron in the compound formed during its interaction with hydrochloric acid is II. |
Electronegativity, oxidation state and valence of chemical elements
Electronegativity
The concept is widely used in chemistry electronegativity (EO).
The property of atoms of a given element to attract electrons from atoms of other elements in compounds is called electronegativity.
The electronegativity of lithium is conventionally taken as unity, the EO of other elements is calculated accordingly. There is a scale of values for EO elements.
The numerical values of EO elements have approximate values: it is a dimensionless quantity. The higher the EO of an element, the more clearly its non-metallic properties appear. According to EO, the elements can be written as follows:
$F > O > Cl > Br > S > P > C > H > Si > Al > Mg > Ca > Na > K > Cs$. Highest value EO has fluoride.
Comparing the EO values of elements from francium $(0.86)$ to fluorine $(4.1)$, it is easy to notice that EO obeys the Periodic Law.
In the Periodic Table of Elements, EO in a period increases with the element number (from left to right), and in the main subgroups it decreases (from top to bottom).
In periods, as the charges of the atomic nuclei increase, the number of electrons on the outer layer increases, the radius of the atoms decreases, therefore the ease of electron loss decreases, the EO increases, and therefore the non-metallic properties increase.
Oxidation state
Complex substances consisting of two chemical elements are called binary(from lat. bi - two), or two-element.
Let us recall the typical binary compounds that were given as an example to consider the mechanisms of formation of ionic and covalent polar bonds: $NaCl$ - sodium chloride and $HCl$ - hydrogen chloride. In the first case, the bond is ionic: the sodium atom transferred its outer electron to the chlorine atom and turned into an ion with a charge of $+1$, and the chlorine atom accepted an electron and turned into an ion with a charge of $-1$. Schematically, the process of converting atoms into ions can be depicted as follows:
$(Na)↖(0)+(Cl)↖(0)→(Na)↖(+1)(Cl)↖(-1)$.
In the $HCl$ molecule, the bond is formed due to the pairing of unpaired outer electrons and the formation of a common electron pair of hydrogen and chlorine atoms.
It is more correct to imagine the formation of a covalent bond in a hydrogen chloride molecule as the overlap of the one-electron $s$-cloud of the hydrogen atom with the one-electron $p$-cloud of the chlorine atom:
During a chemical interaction, the shared electron pair is shifted towards the more electronegative chlorine atom: $(H)↖(δ+)→(Cl)↖(δ−)$, i.e. the electron will not completely transfer from the hydrogen atom to the chlorine atom, but partially, thereby determining the partial charge of the atoms $δ$: $H^(+0.18)Cl^(-0.18)$. If we imagine that in the $HCl$ molecule, as well as in the $NaCl$ chloride, the electron has completely transferred from the hydrogen atom to the chlorine atom, then they would receive charges of $+1$ and $-1$: $(H)↖ (+1)(Cl)↖(−1). Such conditional charges are called degree of oxidation. When defining this concept, it is conventionally assumed that in covalent polar compounds the bonding electrons are completely transferred to a more electronegative atom, and therefore the compounds consist only of positively and negatively charged atoms.
The oxidation state is the conditional charge of the atoms of a chemical element in a compound, calculated based on the assumption that all compounds (both ionic and covalently polar) consist only of ions.
The oxidation number can have a negative, positive or zero value, which is usually placed above the element symbol at the top, for example:
$(Na_2)↖(+1)(S)↖(-2), (Mg_3)↖(+2)(N_2)↖(-3), (H_3)↖(-1)(N)↖(-3 ), (Cl_2)↖(0)$.
Those atoms that have accepted electrons from other atoms or to which common electron pairs are displaced have a negative oxidation state value, i.e. atoms of more electronegative elements.
The oxidation state has a positive value for those atoms that donate their electrons to other atoms or from which common electron pairs are drawn, i.e. atoms of less electronegative elements.
Atoms in molecules of simple substances and atoms in a free state have a zero oxidation state.
In compounds, the total oxidation state is always zero. Knowing this and the oxidation state of one of the elements, you can always find the oxidation state of another element using the formula of a binary compound. For example, let's find the oxidation state of chlorine: $Cl_2O_7$. Let us denote the oxidation state of oxygen: $(Cl_2)(O_7)↖(-2)$. Therefore, seven oxygen atoms will have a total negative charge of $(-2)·7=-14$. Then the total charge of two chlorine atoms is $+14$, and that of one chlorine atom is $(+14):2=+7$.
Similarly, knowing the oxidation states of elements, you can create a formula for a compound, for example, aluminum carbide (a compound of aluminum and carbon). Let's write the signs of aluminum and carbon side by side - $AlC$, with the sign of aluminum first, because it's metal. Using the periodic table of elements, we determine the number of outer electrons: $Al$ has $3$ electrons, $C$ has $4$. The aluminum atom will give up its three outer electrons to carbon and will receive an oxidation state of $+3$, equal to the charge of the ion. The carbon atom, on the contrary, will take the $4$ electrons missing to the “cherished eight” and receive an oxidation state of $-4$. Let's write these values into the formula $((Al)↖(+3)(C)↖(-4))$ and find the least common multiple for them, it is equal to $12$. Then we calculate the indices:
Valence
Very important in the description chemical structure organic compounds has a concept valence.
Valence characterizes the ability of atoms of chemical elements to form chemical bonds; it determines the number of chemical bonds by which a given atom is connected to other atoms in the molecule.
The valence of an atom of a chemical element is determined, first of all, by the number of unpaired electrons participating in the formation of a chemical bond.
Valence possibilities atoms are defined:
- the number of unpaired electrons (one-electron orbitals);
- the presence of free orbitals;
- presence of lone pairs of electrons.
In organic chemistry, the concept of “valence” replaces the concept of “oxidation state”, which is usually used in inorganic chemistry. However, this is not the same thing. Valence has no sign and cannot be zero, while the oxidation state is necessarily characterized by a sign and can have a value equal to zero.
Electronegativity is the property of a chemical element to attract electrons to its atom from atoms of other elements with which this element forms a chemical bond in compounds.
When a chemical bond is formed between atoms of different elements, the common electron cloud shifts to a more electronegative atom, which is why the bond becomes covalently polar, and if the difference in electronegativity is large, it becomes ionic.
Electronegativity is taken into account when writing chemical formulas: in binary compounds, the symbol of the most electronegative element is written at the back.
Electronegativity increases from left to right for elements of each period and decreases from top to bottom for elements of the same PS group.
Valence An element is the property of its atoms to combine with a certain number of other atoms.
There are stoichiometric, electronic valency and coordination number. We will consider only the stoichiometric valence.
Stoichiometric Valency shows how many atoms of another element are attached to an atom of a given element. The valency of hydrogen is taken as the unit of valence, because hydrogen is always monovalent. For example, in the compounds HCl, H 2 O, NH 3 (the correct spelling of ammonia H 3 N is already used in modern textbooks), CH 4 chlorine is monovalent, oxygen is divalent, nitrogen is trivalent and carbon is tetravalent.
The stoichiometric valence of oxygen is usually 2. Since almost all elements form compounds with oxygen, it is convenient to use it as a standard for determining the valence of another element. For example, in the compounds Na 2 O, CoO, Fe 2 O 3, SO 3, sodium is monovalent, cobalt is divalent, iron is trivalent, sulfur is hexavalent.
In redox reactions, it will be important for us to determine the oxidation states of elements.
Oxidation state of an element in a substance is called its stoichiometric valency, taken with a plus or minus sign.
Chemical elements are divided into elements of constant valency and elements of variable valence.
1.3.3. Substances of molecular and non-molecular structure. Type of crystal lattice. Dependence of the properties of substances on their composition and structure.
Depending on the state in which compounds are found in nature, they are divided into molecular and non-molecular. In molecular substances, the smallest structural particles are molecules. These substances have molecular crystal lattice. In non-molecular substances, the smallest structural particles are atoms or ions. Their crystal lattice is atomic, ionic or metallic.
The type of crystal lattice largely determines the properties of substances. For example, metals having metal lattice type, different from all other elements high plasticity, electrical and thermal conductivity. These properties, as well as many others - malleability, metallic luster, etc. conditioned special kind bonds between metal atoms -- metal connection. It should be noted that the properties inherent in metals appear only in the condensed state. For example, silver in the gaseous state does not have physical properties metals
A special type of bond in metals – metallic – is caused by a deficiency of valence electrons, so they are common to the entire structure of the metal. The simplest model of the structure of metals assumed that the crystal lattice of metals consists of positive ions surrounded by free electrons; the movement of electrons occurs chaotically, like gas molecules. However, such a model, while qualitatively explaining many properties of metals, turns out to be insufficient when tested quantitatively. Further development of the theory of the metallic state led to the creation band theory of metals, which is based on the concepts of quantum mechanics.
The sites of the crystal lattice contain cations and metal atoms, and electrons move freely throughout the crystal lattice.
A characteristic mechanical property of metals is plastic, due to the peculiarities of the internal structure of their crystals. Plasticity is understood as the ability of bodies under the influence of external forces to undergo deformation, which remains even after the cessation of external influence. This property of metals allows them to be given different shape in forging, rolling metal into sheets or drawing it into wire.
The plasticity of metals is due to the fact that, under external influence, the layers of ions that form the crystal lattice shift relative to each other without breaking. This occurs as a result of the fact that the moved electrons, due to free redistribution, continue to communicate between the ionic layers. When a solid substance with an atomic lattice is subjected to mechanical action, its individual layers are displaced and the adhesion between them is disrupted due to the breaking of covalent bonds.
ions, then these substances form ionic type of crystal lattice.
These are salts, as well as oxides and hydroxides of typical metals. These are hard, brittle substances, but their main quality is : solutions and melts of these compounds conduct electric current.
If the nodes of the crystal lattice contain atoms, then these substances form atomic type of crystal lattice(diamond, boron, silicon, aluminum and silicon oxides). The properties are very hard and refractory, insoluble in water.
If the nodes of the crystal lattice contain molecules, then these substances form (under normal conditions gases and liquids: O 2, HCl; I 2 organic matter).
It is interesting to note the metal gallium, which melts at a temperature of 30 o C. This anomaly is explained by the fact that Ga 2 molecules are located at the nodes of the crystal lattice and its properties become similar to substances that have a molecular crystal lattice.
Example. All non-metals of the group have a non-molecular structure:
1) carbon, boron, silicon; 2) fluorine, bromine, iodine;
3) oxygen, sulfur, nitrogen; 4) chlorine, phosphorus, selenium.
In non-molecular substances, the smallest structural particles are atoms or ions. Their crystal lattice is atomic, ionic or metallic
At decision It’s easier to approach this question from the opposite direction. If the nodes of the crystal lattice contain molecules, then these substances form molecular type of crystal lattice(under normal conditions, gases and liquids: O 2, HCl; also I 2, orthorhombic sulfur S 8, white phosphorus P 4, organic substances). In terms of properties, these are fragile, fusible compounds.
The second answer contains fluorine gas, the third contains oxygen and nitrogen gases, and the fourth contains chlorine gas. This means that these substances have a molecular crystal lattice and a molecular structure.
IN first The answer is that all substances are solid compounds under ordinary conditions and form an atomic lattice, which means they have a non-molecular structure.
Correct answer:1) carbon, boron, silicon
Part 1. Task A5.
Checked elements: Electronegativity. Oxidation state and
valence of chemical elements.
Electronegativity-a value characterizing the ability of an atom to polarize covalent bonds. If in a diatomic molecule A - B the electrons forming the bond are attracted to atom B more strongly than to atom A, then atom B is considered more electronegative than A.
The electronegativity of an atom is the ability of an atom in a molecule (compound) to attract electrons that bind it to other atoms.
The concept of electronegativity (EO) was introduced by L. Pauling (USA, 1932). Quantitative characteristics electronegativity of an atom is very arbitrary and cannot be expressed in any units physical quantities, therefore, several scales have been proposed to quantify EO. The scale of relative EO has received the greatest recognition and distribution:
Electronegativity values of elements according to Pauling
Electronegativity χ (Greek chi) is the ability of an atom to hold external (valence) electrons. It is determined by the degree of attraction of these electrons to the positively charged nucleus.
This property manifests itself in chemical bonds as a shift of bond electrons towards a more electronegative atom.
The electronegativity of the atoms involved in the formation of a chemical bond is one of the main factors that determines not only the TYPE, but also the PROPERTIES of this bond, and thereby affects the nature of the interaction between atoms during a chemical reaction.
In L. Pauling's scale of relative electronegativities of elements (compiled on the basis of the bond energies of diatomic molecules), metals and organogenic elements are arranged in the following row:
The electronegativity of elements obeys the periodic law: it increases from left to right in periods and from bottom to top in the main subgroups of the Periodic Table of Elements D.I. Mendeleev.
Electronegativity is not an absolute constant of an element. It depends on the effective charge of the atomic nucleus, which can change under the influence of neighboring atoms or groups of atoms, the type of atomic orbitals and the nature of their hybridization.
Oxidation state is the conditional charge of the atoms of a chemical element in a compound, calculated from the assumption that the compounds consist only of ions.
Oxidation states can have a positive, negative or zero value, and the sign is placed before the number: -1, -2, +3, in contrast to the charge of the ion, where the sign is placed after the number.
In molecules, the algebraic sum of the oxidation states of elements, taking into account the number of their atoms, is equal to 0.
The oxidation states of metals in compounds are always positive, the highest oxidation state corresponds to the number of the group of the periodic system where the element is located (excluding some elements: gold Au+3 (group I), Cu+2 (II), from group VIII the oxidation state +8 can only osmium Os and ruthenium Ru.
The degrees of non-metals can be both positive and negative, depending on which atom it is connected to: if with a metal atom it is always negative, if with a non-metal it can be both + and - (you will learn about this when studying a number of electronegativities) . The highest negative oxidation state of non-metals can be found by subtracting from 8 the number of the group in which the element is located, the highest positive is equal to the number of electrons in the outer layer (the number of electrons corresponds to the group number).
The oxidation states of simple substances are 0, regardless of whether it is a metal or a non-metal.
Table showing constant powers for the most commonly used elements:
Oxidation state (oxidation number, formal charge) - an auxiliary conventional value for recording the processes of oxidation, reduction and redox reactions, a numerical value electric charge, assigned to an atom in a molecule under the assumption that the electron pairs performing the bond are completely biased towards more electronegative atoms.
Ideas about the degree of oxidation form the basis for the classification and nomenclature of inorganic compounds.
The degree of oxidation is a purely conventional value that has no physical meaning, but characterizes the formation of a chemical bond of interatomic interaction in a molecule.
Valency of chemical elements -(from Latin valens - having strength) - the ability of atoms of chemical elements to form a certain number of chemical bonds with atoms of other elements. In compounds formed by ionic bonds, the valency of the atoms is determined by the number of electrons added or given up. In compounds with covalent bonds, the valence of atoms is determined by the number of shared electron pairs formed.
Constant valency:
Remember:
The oxidation state is the conditional charge of the atoms of a chemical element in a compound, calculated from the assumption that all bonds are ionic in nature.
1. An element in a simple substance has a zero oxidation state. (Cu, H2)
2. The sum of the oxidation states of all atoms in a molecule of a substance is zero.
3. All metals have a positive oxidation state.
4. Boron and silicon in compounds have positive oxidation states.
5. Hydrogen has an oxidation state (+1) in compounds. Excluding hydrides
(hydrogen compounds with metals of the main subgroup of the first and second groups, oxidation state -1, for example Na + H -)
6. Oxygen has an oxidation state (-2), with the exception of the compound of oxygen with fluorine OF2, the oxidation state of oxygen (+2), the oxidation state of fluorine (-1). And in peroxides H 2 O 2 - the oxidation state of oxygen (-1);
7. Fluorine has an oxidation state (-1).
Electronegativity is the property of HeMe atoms to attract common electron pairs. Electronegativity has the same dependence as that of Nonmetallic properties: it increases along the period (from left to right), and decreases along the group (from above).
The most electronegative element is Fluorine, then Oxygen, Nitrogen...etc....
Algorithm for completing the task in demo version:
Exercise:
The chlorine atom is located in group 7, so it can have a maximum oxidation state of +7.
The chlorine atom exhibits this degree of oxidation in the substance HClO4.
Let's check this: The two chemical elements hydrogen and oxygen have constant oxidation states and are equal to +1 and -2, respectively. The number of oxidation states for oxygen is (-2)·4=(-8), for hydrogen (+1)·1=(+1). Number positive degrees oxidation is equal to the number of negative ones. Therefore (-8)+(+1)=(-7). This means that the chromium atom has 7 positive degrees; we write down the oxidation states above the elements. The oxidation state of chlorine is +7 in the HClO4 compound.
Answer: Option 4. The oxidation state of chlorine is +7 in the HClO4 compound.
Various formulations of task A5:
3. Oxidation state of chlorine in Ca(ClO 2) 2
1) 0 2) -3 3) +3 4) +5
4.The element has the lowest electronegativity
5. Manganese has the lowest oxidation state in the compound
1)MnSO 4 2)MnO 2 3)K 2 MnO 4 4)Mn 2 O 3
6. Nitrogen exhibits an oxidation state of +3 in each of the two compounds
1)N 2 O 3 NH 3 2)NH 4 Cl N 2 O 3)HNO 2 N 2 H 4 4)NaNO 2 N 2 O 3
7.The valency of the element is
1) the number of σ bonds it forms
2) the number of connections it forms
3) the number of covalent bonds it forms
4) oxidation states with the opposite sign
8. Nitrogen exhibits its maximum oxidation state in the compound
1)NH 4 Cl 2)NO 2 3)NH 4 NO 3 4)NOF