Why do you need to write 2 in the lower right corner of some gases?

1.The chemical symbol is preceded by a number to indicate only the number of particles. For example, the number in front of the element symbol indicates the number of atoms, and the number in front of the ion symbol indicates the number of ions.

2.The number in the lower right corner of the element symbol in the chemical formula indicates the number of atoms of an element contained in a molecule. H2O denotes a water molecule.

It is made up of two hydrogen atoms and one oxygen atom.

3.In the upper right corner of the element symbol the number plus + or -, the determination of the number and the symbol: cation.

The number of charges in the band = the number of electrons in the outermost shell of the atom, such as the number of protons in the K atom is 19, and the electron configuration outside the nucleus.

For , the number of electrons in the outermost shell is 1, and the lost electrons are the electrons in the outermost shell, so a potassium ion has a positive charge of 1 unit, anion.

electrons), such as the charge number of the oxygen ion belt = 8 - the outermost number of electrons of the atom = 6-8 = -2. Your own conclusion is that the number of electrons needed to achieve a stable structure is quite correct.

4.How according to the valency.

Write the chemical formula: metal left, non-metal right; Oxygen in oxides is in the back; The number of marked prices is crossed; The number of atoms must not be missed. The valence is mutual.

direct forks; If multiples are about forks; If equal is it.

5.Some elements have so many valences, which one should be used? In specific compounds, its valency can only be judged according to the chemical formula.

If it helps you in your studies, I am very pleased that I have been engaged in chemistry education for many years! "H2O means that the water molecule is composed of one hydrogen atom and one oxygen atom" is wrong, please pay attention to the description of chemical terms.

Represents the number of atoms in a molecule, H2O means that the water molecule is composed of 2 hydrogen atoms and one oxygen atom, you made a mistake, the number in the upper right corner is the charged number of ions, +2 means it has two units of positive charge, and the negative one is the same, in order to achieve a stable structure, the number of electrons required to gain or lose is right? This is correct, you can use cross-multiplication to write the chemical formula, for example, p is positive 5 valence, oxygen is negative bivalent, their chemical formula is oxygen multiplied by 5, phosphorus multiplied by negative 2 (multiplied to become a positive number), it's as simple as that. 5.

Some elements have so many valences, which one should be used? As for this, it depends on the environment used, that is, in chemistry, for example, the chemical valence of iron has positive 2, positive 3 valence, if it is ferric tetroxide, it is positive 3 valence, and ferrous iron is positive bivalent. bar.

Representing the number of atoms, the atom is required to be equilibrium and the outermost valence electrons must be stable

According to the law of conservation of mass, the chemical valence of non-special substances is generally offset by 0. So there will be numbers.

For example, h2 is written as 2 because hydrogen permeability is composed of hydrogen molecules.

Whereas, 1 hydrogen molecule is made up of two hydrogen atoms.

Therefore, the addition of 2 and the rare crude gas is directly composed of the atomic cluster stool.

So don't add it.

Rare gas dendriths, helium, neon, argon, krypton, xenon. Their molecules are all cell subtons, so it is enough to directly represent wild blindness with elemental symbols. No need to write 2....

If you write 2, such as helium, if you write HE2, then others will think that helium is a molecule composed of two proto-spine senzi.

Because the outer layer of the noble gas atom has met the saturation structure, an atom is a noble gas molecule, and the number in the lower right corner of the general one you call refers to the number of atoms contained in a gas molecule....Dousen.

Because noble gases are monoatomic molecules, there is no need to write 2.

Most of the gas elements of the main group of elements are diatomic molecules, that is, the subscript should be written 2. There are some special gases, such as O3, which are polyatomic molecules. Noble gases are all monoatomic molecules, i.e. their gas symbols are their elemental symbols.

Ordinary gases are diatomic molecules, such as hydrogen, chlorine, fluorine, oxygen, nitrogen, etc., which are represented by H2, Cl2, F2, O2, and N2. Noble gases are monoatomic molecules, such as helium, neon, argon, krypton, xenon, radon, which are directly represented by the symbols he, ne, ar, kr, xe, and rn.

What you are talking about should be called a diatomic molecule, which can be a diatomic molecule because a single atom contains unpaired electrons, of course, also pay attention to the properties of the elements, non-metallic elements need to be relatively active to form diatomic molecules, such as: halogen element, oxygen, nitrogen, hydrogen; Among them, only hydrogen is special, although it has a certain metallic property, it is also a relatively active non-metal.

Oxygen exists in the form of molecules, and an oxygen molecule is made up of two oxygen atoms, so there are two in the lower right corner of the chemical formula. There are also hydrogen, nitrogen, and chlorine in the same category. Helium exists in the form of a single atom, so there are no two. There are also rare gases of the same kind, such as helium, neon, argon, krypton, xenon, radon.

Nitrogen nucleus, oxygen, fluorine, chlorine, bromine, iodine vapor, astatine, carbon dioxide, nitrogen dioxide, sulfur dioxide, silicon dioxide.

Sodium peroxide, hydrogen peroxide.

Wait for the state to close, you haven't figured out the valence, let's learn it first.

In addition to rare gases, you basically have to bring 2

All of them are composed of single atoms, and the innate chemical properties of noble gas elements are relatively stable. It is difficult to form chemical bonds on itself or with other elements.

No, band 2 is because Ta is a molecule formed by the combination of two atoms, such as 02, but there are many molecules that are not composed of two identical atoms, such as CO2, O3, He, etc., which are gaseous at room temperature.