Ch.8

• Covalent bond forms by sharing of electrons between two atoms.
• Diatomic molecules have two atoms per molecule eg. Hydrogen
• A shared pair of electrons (or a bond pair) makes a covalent bond
• Covalent bond is directional and acts only between the two atoms involved.
• Covalent bond is the electrostatic attraction between the shared electrons and the two nuclei.
• when atoms of non-metals combine,they attain a stable electronic arrangement by sharing electrons.
• The number of additional electrons needed for an atom to become a molecule is equal to the number of electrons it will contribute to sharing.
• A hydrogen molecule forms a single covalent bond.
• An oxygen molecule forms a double covalent bond
• A nitrogen molecule forms a triple covalent bond
• Covalent compounds start with B, Si, C, P, N, H, S, I, Br, Cl, O, F.
• The name of the second element of a covalent compound should end with ide.
• A prefix ( mono, di, tri, tetra )is added to indicate the number of atoms of an element in the molecule. It is omitted when the other element only forms a compound with one number of that element.
• CH4 is methane
• NH3 is ammonia
• H2O is water
• H2O2 is hydrogen peroxide
• Relative molecular mass is the sum of the relative atomic masses of all atoms in that molecule eg. N2 = Nx2 = 14
• Formula mass is the sum of the relative atomic masses of all atoms in a substance.