Covalent network solid

In a covalent network solid the atoms are joined together by strong covalent bonds.

The covalent bonds are strong in nature and take a great amount of energy to broken. Network covalent substances therefore have relative high melting and boiling points. They are also very hard.

Diamond is composed of carbon atoms in a network covalent array. Diamond is the hardest substance known and has the highest melting point of all the elements. Diamond sublimes at 3642 °C or 6588 °F. 

A dash is used to represent a covalent bond between atoms. The covalent bond consists of two shared electrons. eg. C-C 

A covalent bond is formed between the electrostatic attraction of two positive nuclei and a pair of shared electrons.

The shared electrons are highly localized between the atoms. Unlike metals, the electrons stay local and do not wonder. Network covalent substances therefore have no free electrons and are poor conductors of electricity and heat. 

Covalent bonds are directional in nature. A strong force is needed to break the bonds and covalent substances are brittle.

The following covalent network solid was made by students using toothpicks and chocolate Maltesers.

It however, did not last long!