COVALENT BONDING

HOW DOES IT WORK? Covalent bonding takes place between non- metals atoms only Atoms try to attain noble gas structure by sharing electrons The shared electrons are attracted by both nuclei and this attraction forms the covalent bond Atoms bonded in this way form molecules

Chlorine

Chlorine has atomic number 17 It has 17 protons in its nucleusIt also has 17 electrons 2 in the inner shell8 in the next shell7 in the outer shell CHLORINE We need 2 chlorine atoms These atoms can then share electrons to complete their outer shells A chlorine molecule is formed Also written Cl-Cl or Cl 2

Methane CH 4

Carbon has atomic number 6 It therefore has 6 electrons 2 in the inner shell 4 in the outer shell Hydrogen has just one electron And we need 4 hydrogens Now both carbon and all 4 hydrogens have complete outer shells 4 covalent bonds have been made Covalent bonds can be shown like this. Or like this

Oxygen O 2

Oxygen has atomic number 8 Therefore it has 8 electrons 2 in the inner shell 6 in the outer shell We need a second oxygen To complete the outer shell, they each need to share 2 electrons, so a total 4 electrons are shared The covalent bonds can be shown like this. Or like this O=O

2 Chlorine Cl 2 Iodine I 2 Carbon Dioxide CO 2 Water H 2 O Most covalent compounds have small molecules. They are gases, Liquids or solids with low melting & boiling points.

Covalent bonds can also link atoms in large networks called Giant Structures. These have very high melting points and are often very hard. Diamond – A form of Carbon Graphite– Another form of Carbon Silicon Dioxide (SiO 2 ) Found in sand and quartz