4.2.1 - Covalent Bonding
Covalent bonding is one of the three types of bonding. It involves a pair of electrons being shared between two atoms.
The diagram below shows two fluorine atoms forming a covalent bond.
Two fluorine atoms forming a covalent bond. Each atom contributes one electron to form a shared pair of electrons.
Each fluorine atom contributes one electron to form a pair of electrons which is shared between the two atoms. This shared pair of electrons is circled on the diagram below.
The shared pair of electrons in a covalent bond between two fluorine atoms.
Because these two electrons are shared between the atoms, they are found in the outer shells of both atoms. For this reason, the outer shells of the two atoms are drawn overlapping each other, with the shared pair of electrons inside the overlapping space.
In a covalent bond, each atom usually contributes one electron to the shared pair, however sometimes one of the atoms provides both of the electrons.
The atoms that take part in covalent bonding are usually nonmetal atoms. This is because sharing electrons helps the atoms to move closer to having a full outer shell. Since metal atoms only have a small number of outer shell electrons it is easier for them to get a full outer shell by losing electrons and forming ions than by sharing electrons.
The shared pair of electrons are located between the nuclei of the two atoms. The electrons are negatively charged and the nuclei are positively charged. Therefore, each nucleus is attracted towards the shared pair of electrons by the electrostatic force. The shared pair of electrons is also attracted outwards towards the nuclei.
These forces of electrostatic attraction hold the two atoms together.
In a covalent bond, the two atoms are held together by electrostatic attraction between the positively charged nuclei and the negatively charged shared pair of electrons.
It is common for atoms to be covalently bonded to multiple other atoms. For example, the particle shown below is an ethane molecule. It is made up of two carbon atoms and six hydrogen atoms all held together by covalent bonds. Each carbon atom is covalently bonded to four other atoms.
An ethane molecule. Each carbon atom is covalently bonded to four other atoms.
Flashcards help you memorise information quickly. Copy each question onto its own flashcard and then write the answer on the other side. Testing yourself on these regularly will enable you to learn much more quickly than just reading and making notes.
What happens when two atoms form a covalent bond?
What holds the atoms together in a covalent bond?
Which type of element is usually involved in a covalent bond?
4.2.2 - Single, Double and Triple Covalent Bonds
4.1.1 - Bonding
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