COVALENT BONDING -formed from the sharing of pairs of electrons between atoms of non-metallic elements - Sharing of electrons occurred to satisfy the octet requirements of the atoms

In covalent bonds, electrons are shared between electronegative elements.

Carbon-carbon covalent bonding

PROPERTIES OF COVALENT COMPOUNDS LOW MELTING POINT – few substances have melting points which exceeds 300oC. At room temperature, covalent compounds can exist as a solid, liquid or gas. Indicates weak attractive force between the molecules

SOFT SOLIDS – covalent compound solids are soft at room temperature ELECTRICAL CONDUCTIVITY – whether solid, liquid or gas, covalent compounds are non-conductors of electricity

MOLECULAR COVALENT ELEMENTS DIATOMIC MOLECULES – Fluorine – F2 Chlorine – Cl2 Bromine – Br2 Iodine – I2 Hydrogen – H2 Oxygen – O2 Nitrogen – N2 OTHERS – Phosphorus – P4 Sulfur – S8

NOBLE GASES – exists as neutral atoms NOT molecules He, Ne, Ar, Kr, Xe and Rn atoms

STEPS IN DRAWING LEWIS DOT STRUCTURE OF COVALENT COMPOUNDS Draw the Lewis dot structure of H2O. 1. Determine the central atom – The central atom requires the greatest number of electrons. The other atoms are called the side atoms. Number of valence e- Number of e- needed to satisfy the octet H 1 O 6 2 Side atom Central atom

2. Place the central atom in the middle and surround it with the side atoms.

3. Determine the total number of valence electrons needed to satisfy the octet. 2 H atoms x 2 e- / H atoms = 4 e- 1 O atom x 8 e- / O atom = + 8 e- e- needed for octet 12 e-

EXCEPTIONS TO OCTET RULE ELEMENT VALENCE e- REQUIREMENT HYDROGEN 2 BORON 6 PHOSPHORUS 10

4. Determine the total number of valence atoms available. 2 H atoms x 1 e- / H atoms = 2 e- 1 O atoms x 6 e- / O atom = 6 e- e- available 8 e-

5. Subtract the total number of valence electrons available from the total number of valence electrons needed to determine the number of electrons that must be shared. e- needed for octet = 12 e- e- available = - 8 e- e- that must be shared 4 e-

6. Place the number of shared e- around the central atom 6. Place the number of shared e- around the central atom. Distribute the remaining electrons. H O H X X