About the origin of valency in chemistry

The second floor is correct! On the third floor, there is a mistake about the high-temperature reduction part, the iron burns violently because the speed is too fast to completely oxidize to generate part +2 valence, and the high temperature will not help produce the low-valence state.

The valence state for ionic compounds is to lose the number of electrons gained, and many elements can lose different numbers of electrons, so there are different valence states. For covalent compounds, it is much more complicated, each covalent bond is a pair of shared electrons, which side of the deviation is negative, which side of the deviation is positive, and in many cases (especially for organic matter), positive and negative valence can occur on an atom at the same time, and its valence state is the sum of positive and negative valence.

The valency is defined as follows: for a compound formed from ions, the one that gains electrons is negative, the one that loses electrons is positive, and the number of electrons lost or gained is the absolute value of the compound.

For covalent compounds, the number of shared electron pairs is the absolute value of the chemist, and the side of the shared electron pair bias has a negative valence.

But sometimes much more complex than this, Fe3O4 is an ionic compound that on average one out of every three atoms loses 2 electrons, two loses three electrons, and loses a total of 8 electrons, so it is in the 8 3 valence,

When the noble gas is elemental, the valence is of course zero.

The formation of a compound is not zero-valent.

For example, XE can generate XEF2, XEF4, XEF6, and the valency is +2, +4, and +6 respectively.

Because noble gases are generally more stable, it is difficult to form compounds, and they often exist in elemental form, so they are called group 0 elements.

Modern science has found that they can also participate in reactions, although it is easier to be at the bottom of the periodic table with xe and the like.

Fe3O4 can be regarded as Fe2O3·FeO, so it shows +2 and +3 valence at the same time.

In chemical nomenclature, additional prefixes such as "high", "sub" and "secondary" are often used to indicate the valence state of a certain component element in a compound or the number of atoms.

For example, Fe3+ is an iron ion, then a ferrous ion is Fe2+

The nitrate ion is one more oxygen gen than nitrite, nitrite is NO2, sodium nitrite is nano2, and nitrite is HNO2

It is related to the outermost electrons of the element, and also related to the subouter electron shell, the nth electron shell of the element can hold up to 2n times 2 electrons, such as the first shell can only hold 2 electrons, the second shell can hold up to 8 electrons, the third shell can hold up to 18 electrons, and the subouter shell can not exceed 18 electrons, and the outermost shell cannot exceed 8 electrons. The valency of an element is related to the gain and loss of the outermost electrons, and the outermost shell is the most stable when it is 8 electrons.

All the elements that become ions tend to be in the most stable state, and if the outermost shell is less than 4 electrons, then these electrons are easily lost. When there are more than 4 electrons, it is easy to get electrons and reveal the negative valence.

Valency is the property of an element when one atom is combined with other elements. In general, the valence of valence is equal to the number of electrons gained and lost by each atom during compounding, that is, the number of electrons gained and lost when the element can reach a stable structure, which is often determined by the electronic configuration of the element, mainly the outermost electronic configuration, and of course, it may also involve the substable structure composed of sublayers that can be achieved by the subouter shell.

Valency is the number of chemical bonds formed by one atom of a fluttering element with atoms of other elements. An atom is composed of the nucleus and the electrons on the periphery, the electrons move in layers around the nucleus, and the atoms of the compound are connected to each other by as many bonds as the compound valence. 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 valencies of common compounds are: monovalent hydrogen, sodium, potassium, silver, bivalent calcium, barium, magnesium, zinc, trivalent aluminum, tetravalent silicon, pentavalent phosphorus, ferrous positive bivalent, iron positive trivalent, sulfur.

Two, four, and six eggplant friends, carbon has two and four prices, copper and mercury are generally two valent.

Valency refers to the number of charges that an atom has in a compound, also known as the valency or valence number of an atom. It reflects the number of valence electrons in an atom and is an important parameter to describe the chemical properties of an atom. Normally, the valency of an atom is equal to the number of valence electrons of its atom minus the number of covalent electrons of the atoms attached to it in the compound.

The main role of valency is to describe the chemical reactions between elements and the formation of chemical bonds in the chemical equations of molecules and ionic compounds. In chemical equations, valency can be used to ** the products of chemical reactions, help explain the chemical mechanism of reactions, and can be used to calculate the process of electron transfer and sharing in chemical reactions.

In chemistry, we often use the valency of an element to determine the number of atoms in a compound of an element and the structure of a compound. For example, when we write a chemical equation, we need to know the valency of each atom to determine the number and proportion of atoms in the reaction products and reactants. Therefore, valency is a very important concept in chemistry.

Basic Concepts of Chemical Formula and Valency (1) Significance of Chemical Formula: Macro Significance: A

denotes a substance; b.indicates the elemental composition of the substance; Micro Significance: a

represents a molecule of the substance; b.indicates the molecular composition of the substance; Meaning of quantity: a

Represents the ratio of the number of atoms in a molecule of a substance; b.Indicates the mass ratio of the elements that make up the substance. (2) Reading and writing of elemental chemical formulas directly represented by elemental symbols:

a.Elemental metals. Such as:

potassium K copper Cu silver AG, etc.; b.Solid non-metallic. Such as:

Carbon, C, sulfur, S, phosphorus, etc. CNoble gas. Such as:

Helium (gas), he, neon (gas), ne, ne, argon (gas), ar, etc. Polyatoms constitute the elemental substance of molecules: their molecules are composed of several atoms of the same kind, just write a few in the lower right corner of the element symbol. Such as:

Each oxygen molecule is composed of 2 oxygen atoms, then the chemical formula of oxygen is O2 Diatomic molecule elemental chemical formula: O2 (oxygen), N2 (nitrogen), H2 (hydrogen) Polyatomic molecule elemental chemical formula: ozone O3, etc. (3) Reading and writing of chemical formula of compounds:

Read first and write later, read first and read first Compounds composed of two elements: read"Some-and-so", such as: MGO (magnesium oxide), NaCl (sodium chloride) acid and metal elements composed of compounds:

Read as"A certain acid", such as: KMno4 (potassium permanganate), K2mnO4 (potassium manganate), MGSO4 (magnesium sulfate), CACO3 (calcium carbonate).

4) Judge the valency of the element according to the chemical formula, and write the chemical formula of the compound according to the valency of the element: The basis for judging the valency of the element is: the algebraic sum of the positive and negative valency in the compound is zero.

Steps to write the chemical formula according to the valency of the element: aWrite out the element symbol according to the element valence, positive, left, negative and right, and mark the valence; b.

See if the valence of the element has a divisibility and is reduced to the simplest ratio; c.Cross-inversion writes the valency that has been reduced to the simplest ratio in the lower right corner of the element symbol.

The valency of an element is the number of electrons it gains and loses, for example, the number of outermost electrons in Cl is 7, and the number of 8 electrons is stable, so the valency is -1, which can be understood as one less electron; Na has 1 electron in the outermost shell and 8 in the second shell, so the loss of one electron will form a stable structure, then the valency is +1, which is understood as one more electron; Some elements have variable valence because they can either gain or lose electrons. In covalent compounds, it is a bit more complicated, for example, in H2O2 the O valency is -1, but sometimes it can also be -2 because the outermost shell is 6. For relative molecular mass, you can take a look.

To put it simply, people define the mass of 12c as 12, for example, if there is an element that is 3 times the mass of this element, then its mass is 36Or you can look at the "Carbon-12 is the scale of the International System of Units that defines moles, and the number of atoms contained in 12 grams of carbon-12 is 1 mole." The ratio of the mass of various atoms (or molecules, ions) to one-twelfth of the mass of carbon-12 [1] is defined as the relative atomic mass of that atom, which is measured in 1

In short, this method is used to tell God that it is easy to write.,If you want to use g as a unit, it's too troublesome to write.,And with a negative power.···.