How are Compounds Formed?

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How are Compounds Formed?

Most elements form compounds.

For example: A reaction between sodium and chlorine gives the compound sodium chloride (salt) quite readily.

The noble gases do not usually form compounds. They are different from other elements, since their atoms are described as stable or unreactive. They are stable because their outer electron shell is full. A full outer shell makes an atom more stable.

How are Compounds Formed?

Only the noble gases have full outer shells. This is why they are stable.

Other elements react with each other in order to obtain full outer shells, this makes them more stable.

Depending on their electronic configurations, atoms lose or gain electrons in order to achieve a full outer shell.

Losing electrons

The sodium atom has one electron in its outer shell. If it loses this one electron it will achieve a full outer shell. By losing the one electron to another atom, it becomes a sodium ion.

How are Compounds Formed?

The sodium ion still has 11 protons but by losing one electron it has only 10 electrons compared to the atom. Hence, its overall charge is +1.

This +1 charge is due to the ion having one more proton than electron.

In naming ions, you take the symbol Na and assign a positive charge. This gives us the sodium ion Na+.

Gaining electrons

A chlorine atom has seven electrons in its outer shell. It can reach a full outer shell by gaining one electron. It will then become the chloride ion, Cl-.

A negative charge is assigned to the ion to signify that the ion contains one more electron than proton.

How are Compounds Formed?


Any atom can become an ion if it gains or loses electrons.

An ion is a charged particle. It is charged due to an unequal number of electrons and protons.