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GCSE Chemistry Booster Tutor: Chemical Bonding.

A summary of all you need to know about ionic and covalent bonding.

· GCSE Science Notes

COMPOUNDS form from the chemical bonding of two or more elements. 


IONIC Compounds form when metals and non-metals chemically bond. Ionic bonding involves the transfer of electrons leading to the formation of IONS

For example, sodium (Na) and fluorine (F) react together to form sodium fluoride (NaF).  

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NaF is an ionic compound formed by Na transferring its’ outer shell electron to F. 

A sodium atom is neutrally charged because 11 electrons (-11)and 11 protons (+11) equal 0. When sodium transfers its’ outer shell electron it becomes a positive charge because 10 electrons (-10) and 11 protons (+11) equal +1. Sodium is now a positively charged ion, Na+. A positive charged ion is called a cation.

A fluorine atom is neutrally charged because 9 electrons (-9) and 9 protons (+9) equal 0. When fluorine accepts an electron from sodium it becomes negatively charged because 10 electrons (-10) and 9 protons (+9) equal -1. Chlorine is now a negatively charged ion, Cl-. A negative charged ion is called an anion.

The chemical bond is formed due to the electrostatic forces between the positive and negative charged ions. Na+ Cl- forming NaCl. These electrostatic forces of attraction are strong creating a stable compound. 

In this second example, calcium and chlorine react together to form the compound CaCl2.

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Strong electrostatic forces of attraction between the opposite charged ions require a great deal of energy to separate them so ionic compounds have high melting and boiling points.  

The ions in solid ionic compounds are held firmly in place so they do not conduct electricity. Once melted or dissolved in water the charged ions are free to move so molten and in solution ionic compounds do conduct electricity. 


COVALENT compounds form when non-metals chemically bond. Covalent bonding involves the sharing of electrons leading to the formation of molecules. The atoms are held together by intermolecular forces

For example, two hydrogen atoms will share their outer shell electrons to form a hydrogen molecule (H2). 

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Below are further examples of covalent bonding.

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Covalent compounds have strong intermolecular forces, but they are weaker than the electrostatic forces holding ionic compounds together. Covalent compounds have low melting and boiling points. They do not conduct electricity in any state (with the exception of carbon).