Topic 2 - Covalent bonding

DEFINING COVALENT BONDING

• Many compounds do not conduct electricity, either when dissolved or when molten. These compounds do not contain any ions, which means they contain a different bond between their atoms (covalent bond). 
• Covalent bond= a chemical bond that involves the sharing of electron pairs between atoms. It is formed between non-metal atoms. 
• Covalent compounds are usually gases or liquids (sometimes solids) with low melting points or boiling points and they don't conduct electricity.

• Only the outer electrons in the shell are capable of taking part in bonding. 
• Chlorine and hydrogen can form ionic or covalent bonds, depending on their situation. 

CHARACTERISTICS OF COVALENTLY BONDED SUBSTANCES

• Covalent compounds can form simple molecular crystals, if they are cooled sufficiently. Examples of simple molecular crystals are ice, solid carbon dioxide, solid methane, iodine and solid ammonia. 

• Carbon in the form of diamond has a giant covalent structure. Each carbon atom is bonded to four neighbouring carbon atoms by a covalent bond. These bonds are at the corners of a tetrahedron. Because all the bonds in this solid are covalent, this structure has a very high melting point and it is the hardest substance known. 

• In graphite, another form of carbon, the carbon atoms are very strongly bonded together in a hexagonal formation in sheets. Adjacent sheets are fairly loosely bonded together. These sheets can slide over one another, and this is…