All atoms in the periodic table when they bond are trying to achieve a full outer shell of 8 electrons so they are energetically stable. In order to do this often atoms will share electrons in their valence shell. This is most common in non metal elements as they are often found in groups 15, 16, 17 where they only nee to share 2-3 electrons to achieve a full outer shell.
An example is the element chlorine. Chlorine has 7 electrons in its outer shell and by forming a covalent bond and sharing a pair of electrons each chlorine atom can have 8 electrons in its outer shell.
Depending on the atom will depend on the number of atoms they share. Chlorine only needs to share one pair of electrons meaning it will only form one bond and this is sufficient to complete the outer shell. However looking at an atom of nitrogen, this only have 5 electrons in its outer shell. To achieve a full outer shell of 8 electrons it needs to share 3 pairs. So in total 3 electrons come from one nitrogen atom and 3 from another for a total of 6 that are shared.
A full outer shell is known as the noble gas configuration where the outer shell of an atom is energetically stable and contains 8 outer electrons
The electron is the smallest sub atomic particle that make up the atom. Has a negative charge and is located in shells that orbit the nucleus
A covalent bond forms when two or more atoms share a pair of electrons to form a bond
Non metals are located mainly on the right hand side of the periodic table and comprise of covalently bonded compounds. Non metals share electrons to have a full outer shell.
An atom is the smallest particle that makes up all matter
Elements are atoms with the same number of protons in the nucleus