What is the apparent valence and what is the main valence

The concept of valency learned in middle school should be called "apparent valency" to be precise, sometimes it does not really reflect the existence form of matter, and the effect is only convenient for research, so how convenient is how to come; For the vast majority of cases, the tendency to electron transfer is more obvious, so the valency of the elements in most substances is determined; On this basis, the valency of other elements can be calculated by the apparent form of the chemical formula, which is also accepted, so the valency of the elements in most substances is determined.

It is the valency observed on the surface according to the chemical formula of the molecule.

For example, the apparent valency of iron in ferric tetroxide is +8 3

In fact, the iron in it has a +2 valence and a +3 valence.

===Please, the landlord must choose me*****=Chemistry] Periodic Table Memory Formula.

Valence: One price please donkey feet take silver, (monovalent hydrochloride potassium sodium silver) bivalent sheep Gaimei vest. (divalent oxygen, calcium, magnesium, barium, zinc).

Monovalent potassium, sodium, hydrochloride, silver, divalent oxygen, calcium, barium, magnesium, zinc.

3. Aluminum, 4 silicon, pentavalent phosphorus, 23 iron, 24 carbon.

Nitrogen, copper, mercury, and bivalent are the most common in the first to pentavalent currencies.

Positive copper, potassium, sodium, silver, copper, magnesium, calcium, barium, zinc.

3. Aluminum, 44 silicon, 46 sulfur, 245, nitrogen, 35 phosphorus.

157 chloro23 ferric 2467 manganese is positive.

Carbon has positive four and positive two, and then keep the negative price in mind.

Negative iodine monobromo, with fluorochlorofluorocarbon, negative dioxysulfur, trinitrogen, phosphorus.

Common atomic group valence decision in junior high school:

Negative hydroxide mononitrate, negative disulfate carbonate, and negative triphosphate, only ammonium is positive monohydrohelium, lithium beryllium boron, carbon, nitrogen, oxyfluorone. Sodium, magnesium, aluminum, silicon, phosphorus, sulfur, chloride, argon, potassium, calcium.

To remember the valency, we often use the following formula:

Monovalent potassium hydrochloride, sodium silver, bivalent calcium, magnesium, barium oxygen, zinc. Two copper, three aluminum, four seven manganese, two four hexasulfur, two four carbon, three valent nitrogen and phosphorus, iron have two or three to remember.

The order of metal activity can be memorized according to the following formula:

Potassium, calcium, sodium, magnesium, aluminum, zinc, iron, tin, lead, hydrogen, copper, mercury, silver, platinum.

The valency observed on the surface according to the chemical formula of the molecule.

For example, copper has positive bivalent and positive bivalent, when the main valence is positive bivalent.

It can only be said that there is no definite correspondence.

Don't be confused: the chemical bond is known only by knowing the structure, while the valency can be obtained by apparent calculation, because the sum of the product of the valency of the elements of the compound and its coefficient is 0There are one or several valencies of the elements that are commonly used.

Valency is only a rough representation of the strength or weakness of an element's electron ability. For example, although the valency of NaCl in NaCl is 1 and Cl is -1, H in HCL is also 1, and Cl is also -1But the former is an ionic compound, and the electrons of Na are completely given to Cl, while the latter is the electron part of H is lost, and Cl only gets some electrons, but the representation is still the same.

The number of chemical bonds can only be known by writing their structural formulas, and many even common compound structures are relatively complex, such as the structure of carbonate in Na2CO3, as well as Na2SO4, CO, NO, etc. Common ones we know such as CO2 linear structure, two double bonds.

Valency is the number of atoms of an element that combine with each other.

NaCl has a valency of 1 for sodium chloride and 1 for chlorine

The hydrogen element in the compound is usually 1-valent and the oxygen element is usually 2-valent.

Metallic elements usually have a positive valence, non-metals with hydration have a negative valence, and oxidation has a positive valence.

The valency of the elements in the element is 0

There are elements with variable valency that exhibit different valencies in different compounds.

The valency of the atomic cluster is numerically the same as the number of charges of the corresponding ions.

The algebraic sum of positive and negative valencies in a compound is 0

Valence is the number of chemical bonds that one atom of an element forms with the atoms of other elements. An atom is made up of a nucleus and electrons on the periphery, the electrons move in layers around the nucleus, and the atoms of a compound are connected to each other by as many bonds as the valence.

The valence electrons around the element form valence bonds, monovalent atoms can form one covalent bond, and bivalent atoms can form two bonds or one bond plus one bond. Valency is the number of electrons gained or lost by atoms in a substance, or the number of shifts in shared electron pairs. Valency is also a property exhibited by an element in the formation of a compound.

The valency in universities is not the same as the valence in secondary schools, and the valency in secondary schools is defined as the oxidation number in universities

Definition: The apparent charge number of an atom of an element, which is calculated by assuming that the electrons in each chemical bond are assigned to the atom that is more electronegative.

Oxidation number, also known as oxidation state, is a chemical concept developed on the basis of the valency theory and the concept of element electronegativity, which to a certain extent marks the combined state of the element in the compound. When leveling the redox reaction equation according to the rise and fall of valency and electron transfer, it is often difficult to determine the valency number of elements for other substances except simple ionic compounds. For some complex compounds or clusters of atoms, it is more difficult to determine their electron transfer in the reaction, and thus it is difficult to represent the valence state of the elements in the substance.

The so-called "central atom valency method" should be the "when the central atom is at the most ** and the coordination atom is the same, the molecule is a non-polar molecule", right?

The reason for this is that when the central atom is at its most **, all the valence electrons are generally bonded, so that the molecule nanoscatter mode will form a symmetrical configuration. In addition, the coordination atoms are all the same, and the natural molecule will be a slow polar molecule.

The increase or decrease refers to the actual value of the valence.

Electrons are negatively charged, and each electron carries 1 unit of negative charge.

1 electron is obtained, and the valency is reduced by 1 valence; Loss of 1 electron valence increases by 1 valence.

Oxygen, -2 valence, becomes -3 valence when one electron is obtained? -2 becomes -3, decreases: oxygen, -2 valence, loses one electron and becomes -1 valence? -2 to -1, elevated.

"The algebraic sum of the positive and negative valencies of various elements in a compound is equal to zero", which means that the total valency of various elements in a compound adds up to zero. As.

For example, Fe2O3 Fe +3 Valence O -2 Valence +3*2+(-2)*3=0

Alcl3 Al +3 Cl -1 +3 +(-1)*3=0

Another example is NaCl, where the Na element is positive and the Cl element is negative valence, then the sum of positive and negative valency is 0

There are special cases such as ferric tetroxide, some organic matter, etc., which cannot be simply determined by chemical valence.

Generally, they are chemical compounds, and if they are elemental, they do not have electrons.

Only the above rules, the following questions are examples:

kmNO4, find the valency of the Mn element (o is -2 valence, k is +1 valence).

Solution: Let the valency of Mn be x, then it is obtained by the algebraic sum of the positive and negative valencies of various elements in the compound as zero.

1+x+4×（-2）=0

x=+7 valence.

Note: The valence value must be preceded by a + or - sign.

For example, if Al is +3 valence, then the valency algebra is +3, the ion of Cl is -1 valence, and the valency algebra is -1, and there is one Al ion and 3 Cl ions in the aluminum chloride compound, so the sum of the valency algebra of aluminum chloride is +3+3*(-1)=0

It is the sum of the valencies of the elements, and the algebraic sum of the valencies of the compound is 0

The sum of the valencies of all the ions of a substance.

Middle and high schools can be considered equal.

In university inorganics, the oxidation number of elements can be determined according to the following rules: 1The oxidation number of the element in the element is zero.

2.In ionic compounds, the oxidation number of an element is the charge number of the element's ions. 3.

In covalent compounds, when two atoms share a pair of electrons assigned to an atom with a higher electronegativity, the number of formal charges possessed by each atom is their oxidation number.

In junior high and high school, in fact, the so-called "valence" generally refers to the oxidation number. However, the oxidation number and valency are different in strict terminology, and the oxidation number is a visual manifestation of the gain and loss (offset) electrons of an element in a compound; Valency is the bonding ability of an atom (the number of chemical bonds formed with the bonded atom). For example, in hydrogen peroxide hooh, the oxidation number of element O is -1, but the valency is still 2

Generally speaking, the original outer layer of electricity has lost low negative valence, and the electricity is complete, and the 8 electricity stable structure is exceptional, which is priceless than oxygen. Thank you.