Covalent Bonds

• Complete the Molecular Compounds worksheet.
• Covalent bonding involves the sharing of electrons between atoms, with the attraction between the atoms being called a covalent bond.
• A molecular compound consists of two non-metal atoms.
• Molecular compounds have low melting points and are not electrolytes, meaning they do not conduct electricity as a solid or a liquid because they do not contain ions.
• Covalent compounds are held together by the sharing of electrons, with a pair of electrons shared in this way being known as a covalent bond.
• Covalent bonding can be described using Lewis Dot Diagrams, where the electrons can be arranged around each atom so that single electrons can be more easily paired with those of the next atom.
• Molecules of each of these examples can be represented by molecular models, with the “sticks” between the elements representing the shared electrons or covalent bonds.
• Water (H2O) is the most commonly available molecular compound on Earth and is known as the “universal solvent”.
• Ammonia (NH3) is used in window cleaners and in the production of fertilizers.
• Nitric oxide (NO) is an air pollutant produced in the automobile engine when gasoline is burned.
• Covalent Bonding - Multiple Bonds: Electrons are shared as pairs, with some compounds sharing in fours or sixes, giving rise to single, double and triple covalent bonds.
• Examples of molecular compounds include: carbon monoxide, CO; carbon dioxide, CO2; sulfur trioxide, SO3; tetraphosphorus pentasulfide, P4S5; and diphosphorus pentasulfide, P2S5.
• Naming & Writing Molecular Compounds: The first word in the name of a molecular compound is the name of the atom furthest to the left of the periodic table, the second word is the name of the other atom with the ending changed to –ide, and prefixes are used to indicate the number of atoms in the compound.
• Writing Formulas:If you see a prefix in front of either or both of the elements, you do not need to balance the charges, just use the prefixes to determine the subscripts.
• Writing Formulas for Molecular Compounds:Prefixes indicate the number of atoms of each element that are present in a molecule, write the chemical symbol for the first element with the number of atoms (indicated by the prefix) as a subscript and do the same for the second element.
• Diatomic Molecules: Two chlorine atoms share a pair of electrons to form Cl2, a diatomic molecules (di means two), these atoms will always exist in pairs.
• Most of the compounds we encounter are molecular compounds, which are extracted from fossil fuels (coal, oil, and natural gas).
• The driving force for covalent bonding is the attainment of outer electron shells that are completely full, which is achieved by sharing electrons where the shared electrons count towards the outer shells of both atoms.
• Sometimes this is achieved with equal numbers of each type of atom, sometimes it is not.
• In the case of chlorine (2,8,7), it needs 1 more electron to attain a full electron shell.