Anion is an atom that has gained one or a few electrons due to external effects, bringing the number of electrons in its outermost layer to a stable structure. The smaller the radius of the atom, the stronger the ability to gain electrons, and the weaker the metallic properties. Anion is a negatively charged ion, the number of nuclear charges = the number of protons & lt; the number of electrons outside the nucleus, the number of negative charges is equal to the number of electrons obtained by the atom.
The smaller the radius of the atom's ability to absorb electrons is also the stronger, the easier it is to form an anion, the stronger the non-metallic nature. The most non-metallic element is fluorine. Atoms with more than 4 electrons in their outermost layer form anions (non-metallic substances show negative valence, and anions are represented by the symbol "-".)
Expanded Information:
Experimental principle
There are 13 common anions as follows: SO42-, SiO32-, PO43-, CO32-, SO32-, S2O32-, S2-, Cl-, Br-, I-, NO3-, NO2-, Ac-
Among the anions, some are easy to decompose in contact with acid, and some are oxidized and reduced and cannot **** survive. Reduction and can not **** exist. Therefore, the analysis of anion has the following two characteristics:
Anion is easy to change in the process of analysis, is not easy to carry out a lot of formalities of systematic analysis.
Anions have few chances to ****exist with each other, and there are many special effect reactions available, so it is possible to analyze them separately.
In the analysis of anions, the main use of separate analysis methods, only in the identification of certain anions in the case of mutual interference, it is appropriate to take the means of separation.
But the use of separate analysis method, not for the study of all the ions one by one test, but first through the preliminary experiments, with the elimination method to exclude the anion that certainly does not exist, and then on the possible existence of anions to be determined one by one.
Baidu Encyclopedia - Anions