Unit 9: Covalent Bonding Chapters 8 & 9 Chemistry 1K Cypress Creek High School

Chemical Bonding Bonds are the attractive force between atoms or ions in a compound and depend upon: The electron configuration (involves valence electrons) Electronegativity Why do elements bond? To achieve a stable electron configuration (8 electrons; noble gas configuration) » Octet rule – atoms lose, gain or share electrons to achieve a stable configuration of eight valence electrons To achieve the lowest possible energy state (lowest potential energy)

Ionic Properties Review Ionic Bonds Properties: – Exhibit a crystal structure – Exist as solids – Dissolve easily in water – Have high melting and boiling points – Conduct electricity in solutions – Have high electronegativity differences

Covalent Compound Properties Properties of Covalent Compounds – Have low melting and boiling points – Do not dissolve easily in water – Do not conduct electricity in solutions – Exist as gases, liquids, or solids – Have low electronegativity differences

Common Covalent Compounds Nitrous oxide (N 2 O) is laughing gas used as an anesthetic and to boost auto engine power Hydrogen peroxide (H 2 O 2 ) is used as a bleaching agent, emetic (induces vomiting), and an antiseptic (clean cuts and scrapes) Methane (CH 4 ) is a flammable gas used as fuel and in homes for domestic heating and cooking purposes. Sugars, like sucrose (C 12 H 22 O 11 ) and glucose (C 6 H 12 O 6 ), are used in food and energy production

Common Covalent Compounds: CO 2 Carbon dioxide (CO 2 ) is a gas used by plants during photosynthesis, produced in respiration; it is a byproduct of burning fossil fuels, and it has many uses as a fire extinguisher, refrigerant (dry ice), and carbonation in drinks

Common Covalent Compounds: H 2 O Water (H 2 O) is a liquid that is vital for life. It covers about 71% of earth’s surface, and makes up about 60% of the human body. It is known as the universal solvent, and has many unique properties and uses.

Covalent Bonds A Covalent Bond occurs when valence electrons are shared between atoms (usually between nonmetallic elements) Covalently bonded compound known as a molecule – These shared electrons are part of the valences of all atoms involved (satisfies octet rule) Since electrons are shared, no charges appear Many combinations can occur between two nonmetals – Example: carbon and oxygen can form carbon monoxide (CO) and carbon dioxide (CO 2 ) Carbon Dioxide

Covalent Nomenclature Naming (for covalent with 2 elements): – Name the 1st element with prefix to indicate the # of atoms (only if more than one) – Name the 2nd element Use prefix to indicate the number of atoms present Drop the ending of the elements name and use “ide” ending – Example: NCl 3 = nitrogen trichloride mono-di-tri-tetra-penta-hexa-hepta-octa-non-deca- Prefixes:

Covalent Nomenclature Practice NameFormula P2O5P2O5 N2ON2O SF 6 oxygen dichloride dinitrogen trioxide carbon monoxide OCl 2 CO N2O3N2O3 diphosphrous pentoxide dinitrogen monoxide sulfur hexafluoride