Anions

Do you know how the discovery of iodized salt took place? People were suffering from thyroid gland difficulties due to a lack of iron, and that is when iodide anion was added to table salt. The subject of Chemistry has brought the beautiful concept of the anion before us. In simple terms, it is nothing but the negatively charged ion, same as cations which are positively charged ions. The cations and anions are formed when a metal loses its electron, and the same is being gained by a non-metal. The electrostatic attraction between the positive electron and negative electron leads to the formation of an ionic compound, which can be an anion or a cation.

If an atom has a balanced number of electrons and protons, that is, negative and positive charges, it will remain neutral. However, if the balance is not struck and either protons or electrons are more, the charged species formed is called an ion.

A cation has more protons than electrons, so it is a positively charged one. The formation of cations takes place when one or more electrons are lost.

How are Anions Formed?

By now, you must have understood anion’s meaning as the negative ions formed due to the gain of electrons by a non-metal atom. An anion thus has more electrons than the number of protons giving it a net negative charge. They are called anions because they are attracted toward the anode, which is a positive field in an electric field. They usually have the electron configuration of a noble gas. For the classification and measurement of the anion structure, colourimetric approaches are used in conventional wet chemistry.

Valence Electrons- what you must know?

The elements present in Group 17 have seven electrons because of the outer configuration being ns2np5. Hence, they will gain one electron to become an anion with a charge of -1. Similarly, Group 16 elements will form an anion with a charge of -2 and Group 15 with -3.

Cation vs. Anion- Periodic Table

The atom’s position in the periodic table can be intelligently used to predict whether it will form an anion or a cation. For instance, the Halogens always lead to anions, whereas alkaline earth metals and alkali metals usually form cations. Metals such as silver, iron, and nickel form cations, and non-metals such as carbon, oxygen, and sulfur form anions. 

Elements forming both cations and anions

Yes, you heard it right! There are certain elements that can form either cation or anion depending upon the given conditions. For instance, let’s consider Hydrogen, it can gain as well as lose an electron; thus can easily form either anion or cation. An anion example for Hydrogen will be a hydride compound like ZnH2, and a cation example would be a hydrogen compound, namely, H2O.

Naming of Anions

Yes, we all have a name by which we are called, then, why anions should be left behind. If we go through the cations and anions list, we can notice the different processes used to name cations and anions. But, anions have a particular naming procedure that is slightly different from the way the cations are being named. Let’s understand in detail:

• The end part of the element’s name is dropped for naming an anion, and the same is replaced with a suffix -ide
• The number of electrons gained to form an anion is indicated after the chemical symbol
• The charge present on the anion is indicated using a superscript

For instance, if we consider the anion example, F- is the fluoride ion, and O2- is the oxide ion. Here the charge values are given in superscript to indicate anion.

Here is a common list of anions along with their symbol and charge:

Uses of Anions

The anions have a varied use in common life. The ionic properties of the anions have been used by chemists for different purposes. If we consider the anion example of Fluoride, it is widely used in water supplies and is known for preventing the decay of teeth. On the other hand, chloride is a known component that maintains ion balance in the blood. Iodide ion, as already mentioned, is needed for the making of the thyroxine hormone by the thyroid gland.

Cations and Anions: Differences

If we go through the cations and anions list, both sound like two sides of the same coin carrying striking differences. Let’s understand the differences between the two to ace the subject:

• Charge

As already mentioned above, the cations have more protons in their ion balance; thus, they are positively charged, whereas the anions carry more electrons. Thus they are negatively charged.

• Electrode attraction

As Cations are carrying the positive charge, they are attracted to the negative electrode, i.e., cathode, and are thus called cations. On the other hand, anions being net negatively charged are attracted to the positive electrode, i.e., anode.

• Formation

The metallic atoms usually loosely hold their electrons and consequently, they lose the electrons for the formation of the positively charged ion. Alternatively, the non-metallic atoms attract the electrons strongly and so easily gain electrons for the formation of anions. Thus, the cations are formed when a metal atom loses its electrons, and anions are formed when a nonmetal gains an electron.

Formation of ionic Compounds

Another important topic related to anions is the ionic compounds and their formation. When the atoms from the metallic and non-metallic elements combine, the non-metallic atoms tend to draw away the electrons from the metallic atoms to form ions. The oppositely charged ions get attracted to one another to form ionic bonds and produce ionic compounds. The overall net charge present in these ionic compounds is zero. 

Example of ionic compound- Sodium Chloride i.e common salt

2Na + Cl2  →  2Na+ + 2Cl-

Here Sodium belongs to Group 1 metal and has a +1 charged cation. Chlorine, on the other hand, being a non-metal, comes with a -1 anion.

A few other examples of ionic compounds include Calcium chloride (CaCl2), Magnesium Oxide (MgO), and Potassium Iodide (KI).

Conclusion

The world of metals and non-metals is full of magic, cations and anions being one of them. The formation of anions is because of the addition of one or more electrons in the outer shell of the atom. As anions are negatively charged ions, the number of electrons present is greater than the number of protons. Anions are usually named by dropping the end of the element name and adding a suffix of -ide-.