Why does iron ion have 2 3 valence while there are no other valence states like 4 valence etc.

This is determined by the electron distribution of the iron atom, and what is the right valence depends on the degree of stability after the addition or decrease of electrons outside the nucleus.

There is still a +6 price, as for you saying that there is no +4, it is because it is unstable in this state.

Different colors are different for different states:

The 2-valent iron ions in the solution are light green, and the 3-valent iron ions are yellow-green;

When a precipitate is formed, the ferric 2-valent ions are reddish-brown and the ferric 3-valent ions are yellow.

The difference between the two in solution:

The solution containing Fe2+ --- light green.

The solution containing Fe 3+ --- yellow.

Solution containing Cu2+ --- blue.

If both Fe2+ and Fe3+ are present, the yellow color will mask the light green, and the solution will appear yellow. If it also contains Cu 2+, it will be green.

When is the difference between 3-valent iron ions and 2-valent iron ions

Iron loses two electrons when it reacts with sulfur, copper sulfate solution, hydrochloric acid, dilute sulfuric acid, etc., and becomes +2 valence. It reacts with Cl2, Br2, nitric acid and hot concentrated sulfuric acid to be oxidized to Fe3+.

Fe3O4 formed by the reaction of iron with oxygen or water vapor can be regarded as FeO·Fe2O3, of which 1 3 Fe is +2 valence and 2 3 is +3 valence. The +3-valent compound of iron is relatively stable. The oxidation of iron ions is greater than that of copper ions, and iron elements can reduce copper ions, which can naturally reduce iron ions.

How to test for +2 ferric ions and +3 ferric ions:Two test tubes were respectively filled with +2 valence iron ions and +3 valent iron ion solutions, respectively, the KSCN solution was added dropwise, and the +3 ferric ions that immediately turned blood-red were the +2 ferric ions, and the ones that did not change color only turned blood-red after adding the newly made chlorinated water were +2 ferric ions.

The light green solution observed in normal observation must be +2 valence iron ions, and the yellow solution may be +3 valence iron ions.

The relative atomic mass of valence iron.

2. The relative atomic mass of ferric ions.

3. Relative molecular mass foci of ferric iron.

4. Comparison of the radius of ferric ions and ferric ions of iron atoms and ferric ions.

1.The relative atomic mass of the ferric ion is 56.

2.The first atom consists of a nucleus.

and electrons, the mass of the atom is mainly concentrated in the nucleus, and the ferric ion loses only two electrons than the atom, so the atomic mass remains unchanged.

3.Relative atomic Mass: The ratio of the average atomic mass of any atom to one-twelfth of the mass of a carbon 12 atom is called the relative atomic mass of the atom.

4.Atomic weight.

is a unit of mass, which is defined as one-twelfth of the mass of a carbon dodec atom.

Divalent iron ions are converted into ferric ions: Fe2+, and oxidized with oxidants to Fe3+, commonly used are Hno3, H2O2, Cl2

Trivalent iron ions are converted into divalent iron ions: Fe3+, and reduced to Fe2+ with reducing agents, commonly used are Fe, Cu, and I-

Fe encounters weak oxidants, such as S, Fe3+, H+ becomes Fe2+, Fe encounters strong oxidants, such as Hno3, Cl2, becomes Fe3+, excess Fe can also be obtained by reacting with Hno3, this is not the relationship between Hno3, at the beginning, Hno3 oxidizes Fe to Fe3+, but excess Fe restores Fe3+.