CIE AS Chemistry (9701) exams from 2022

Revision Notes

1.3.7 Covalent Bonding

Covalent Bonding: Definition & Examples

  • Covalent bonding occurs between two nonmetals
  • A covalent bond involves the electrostatic attraction between nuclei of two atoms and the bonding electrons of their outer shells
  • No electrons are transferred but only shared in this type of bonding

Chemical Bonding Defining Covalent Bonds, downloadable AS & A Level Chemistry revision notes

The positive nucleus of each atom has an attraction for the bonding electrons shared in the covalent bond

  • Non-metals are able to share pairs of electrons to form different types of covalent bonds
  • Sharing electrons in the covalent bond allows each of the 2 atoms to achieve an electron configuration similar to a noble gas
    • This makes each atom more stable

Covalent bonds & shared electrons table

Chemical Bonding Table_8, downloadable AS & A Level Chemistry revision notes

Dot & cross diagrams

  • Dot and cross diagrams are used to represent covalent bonding
  • They show just the outer shell of the atoms involved
  • To differentiate between the two atoms involved, dots for electrons of one atom and crosses for electrons of the other atom are used
  • Electrons are shown in pairs on dot-and-cross diagrams

Single covalent bonding 

Hydrogen, H2

Chemical Bonding Single Covalent Bonding Hydrogen, downloadable AS & A Level Chemistry revision notes

Covalent bonding in hydrogen

Chlorine, Cl2

Chemical Bonding Single Covalent Bonding Chlorine, downloadable AS & A Level Chemistry revision notes

Covalent bonding in chlorine

Hydrogen Chloride, HCl

Chemical Bonding Single Covalent Bonding HCl, downloadable AS & A Level Chemistry revision notes

Covalent bonding in hydrogen chloride

Ammonia, NH3

Chemical Bonding Single Covalent Bonding Ammonia, downloadable AS & A Level Chemistry revision notes

Covalent bonding in ammonia

Methane, CH4

Chemical Bonding Single Covalent Bonding Methane, downloadable AS & A Level Chemistry revision notes

Covalent bonding in methane

Ethane, C2H6

Chemical Bonding Single Covalent Bonding Ethane, downloadable AS & A Level Chemistry revision notes

Covalent bonding in ethane

Double covalent bonding

Oxygen, O2

Chemical Bonding Double Covalent Bonding Oxygen, downloadable AS & A Level Chemistry revision notes

Covalent bonding in oxygen

Carbon dioxide, CO2

Chemical Bonding Double Covalent Bonding CO2, downloadable AS & A Level Chemistry revision notes

Covalent bonding in carbon dioxide

Ethene, C2H4

Chemical Bonding Double Covalent Bonding Ethene, downloadable AS & A Level Chemistry revision notes

Covalent bonding in ethene

Triple covalent bonding

Nitrogen, N2

Chemical Bonding Triple Covalent Bonding, downloadable AS & A Level Chemistry revision notes

Covalent bonding in nitrogen

  • In some instances, the central atom of a covalently bonded molecule can accommodate more or less than 8 electrons in its outer shell
  • Being able to accommodate more than 8 electrons in the outer shell is known as ‘expanding the octet rule’
  • Accommodating less than 8 electrons in the outer shell means than the central atom is ‘electron deficient’
  • Some examples of this occurring can be seen with Period 3 elements

Chemical Bonding Expanding the Octet Rule SO2, downloadable AS & A Level Chemistry revision notes

Sulfur dioxide, SO2 – dot and cross diagram

Chemical Bonding Expanding the Octet Rule PCl5, downloadable AS & A Level Chemistry revision notes

Phosphorus pentachloride, PCl5 – dot and cross diagram

Chemical Bonding Expanding the Octet Rule SF6, downloadable AS & A Level Chemistry revision notes

Sulfur hexafluoride, SF6 – dot and cross diagram

Exam Tip

Covalent bonding takes place between two nonmetal atoms.

Remember to use the Periodic Table to decide how many electrons are in the outer shell of a nonmetal atom.

Author: Francesca

Fran has taught A level Chemistry in the UK for over 10 years. As head of science, she used her passion for education to drive improvement for staff and students, supporting them to achieve their full potential. Fran has also co-written science textbooks and worked as an examiner for UK exam boards.
Close

Join Save My Exams

Download all our Revision Notes as PDFs

Try a Free Sample of our revision notes as a printable PDF.

Join Now
Already a member?
Go to Top