Covalent Compounds January 2015

Covalent Compounds Covalent Bond – chemical bond that results from sharing electrons Molecule – formed when two or more atoms are bonded covalently

Naming Binary Compounds First element named first Second elements ending is changed to –ide Use prefixes to indicate the number of each atom Examples: N2O – dinitrogen monoxide CCl4 – carbon tetrachloride

Prefixes Mono – Di- Tri- Tetra- Penta- Hexa- Hepta- Octa- Nona- Deca-

Diatomics There are seven elements that always exist as diatomics Always exist bonded to themselves in nature Example: H2 H BrONClIF or BrINClHOF

Practice – Name or give the Formula NF3 P2O5 F2 OBr2 BF3 CH4 NO BN Carbon disulfide Selenium Nitrogen trihydride Sulfur dioxide Phosphorous pentabromide Xenon hexafluoride Tetraarsenic decoxide Trinitrogen nonoxide

Answers Nitrogen trifluoride Diphosphorus pentoxide Fluorine Oxygen dibromide Boron trifluoride Carbon tetrahydride Nitrogen monoxide Boron mononitride CS2 Se NH3 (ammonia) SO2 PBr5 XeF6 As4O10 N3O9

Naming Binary Acids Contains Hydrogen and one other element The first word has the prefix hydro- , the rest of the first word consists of the root of the second element plus the suffix –ic The second word is always acid Example HCl : hydrochloric acid H2S : hydrosulfuric acid

Practice HBr HI H3P Hydrofluoric acid Hydroselenic acid Hydrochloric acid Hydrobromic acid Hydroiodic acid Hydrophosphoric acid HF H2Se HCl

Naming Oxyacid's Contains both a hydrogen and an oxyanion (polyatomic) Keep the root of the oxyanion Include prefixes per- and hypo- as part of the name If the oxyanion ends in –ate replace with –ic If the oxyanion ends in –ite replace with –ous The second word is acid Example HNO3 : nitric acid HClO : hypochlorous acid

Practice H2SO4 HClO4 H3PO4 Carbonic acid Acetic acid nitrous acid Sulfuric acid Perchloric acid Phosphoric acid H2CO3 HC2H3O2 HNO2

What is the formula for hydroxic acid? H2O HOH

Formation of Covalent Bonds

Look at Fluorine Fluorine has 7 valence electrons, it needs 1 more electron to form an octet As two fluorine atoms approach one another attractive forces and repulsive forces act upon the two atoms Once that atoms are close enough together they bond covalently to form a fluorine molecule.

Structures Electron Dot Structure Lewis Structure

Practice – Lewis Structures PH3 H2S CCl4

Answers or

Single Covalent Bonds They are also called sigma bonds (σ) Sigma bonds occur when the shared pair of electrons is centered between the two atoms

Multiple Covalent Bonds Atoms can share more than one pair of electrons with another atom Double or Triple bonds Oxygen and Nitrogen Multiple covalent bonds consist of one sigma and at least one pi bond (π) Pi bonds form when parallel orbitals overlap and share electrons

How many Sigma and Pi bonds are there? C2H2 C2H4

More Lewis Structures NF3 CO2 SiF4 CH4 OCl2 NCl3