Covalent Bonding Sharing is caring 1 Transfer Electrons Unit Cell Ionic Molecule Metallic Delocalized Electrons (sea of e-) 2 Covalent Share Electrons In covalent bonding, atoms still want to achieve a noble gas configuration (the octet rule). But rather than losing or gaining electrons, atoms share electrons. 3 Covalent Bonds When one nonmetal shares one or more electrons with an atom of another nonmetal so both atoms end up with eight valence electrons 4 But rather than losing or gaining electrons, atoms now share an electron pair. The shared electron pair is called a bonding pair 5 Naming Covalent Compound 6 Covalent bonding Makes molecules Specific atoms joined by sharing electrons Two kinds of molecules: Molecular compound Sharing by different elements Diatomic molecules Two of the same atom O2 N2 7 Diatomic elements There are 7 elements that always form molecules: H2 , N2 , O2 , F2 , Cl2 , Br2 , I2 The –gens (hydrogen, nitrogen, oxygen and halogens) 8 NEVER FOUND AS SINGLE ATOMS if “alone” Their names are just the name of the element Oxygen by itself means O2 1 and 7 9 Covalent Bond Video Binary Molecular Compounds Steps to name compounds a. b. c. d. 10 Name first element - use entire name Name second element- change ending to –ide Prefixes used to indicate number of each atom Only time that no prefix is used is if the first is a one Examples: CCl4 – As2O3 – carbon tetrachloride di arsenic tri oxide The Prefixes Mono-monocle Tetra-Tetris 11 Di-Dialogue Tri- tricycle Penta- pentagon Octa- octopus 1 mono 2 di The first vowel is often dropped to avoid the combination of “ao” or “oo”. 3 tri 4 tetra CO = carbon monoxide (monooxide) 5 penta P4O10= tetraphosphorus decoxide 6 hexa 7 hepta SO2= sulfur dioxide (doxide) 8 octa 9 nona 10 deca 12 Molecular Nomenclature: Examples • CF4 • carbon tetraflouride • N 2O • dinitrogen monoxide • SF6 • sulfur hexafluoride 13 P2O3 • diphosporus trioxide IF7 • iodine heptafluoride More Molecular Examples • arsenic trichloride • AsCl3 • dinitrogen pentoxide • N2O5 • tetraphosphorus decoxide • P4O10 14 Covalent Bonds and Lewis Structures Octet Rule: All elements will have 8 electrons around it through a combination of shared and unshared electrons. THERE ARE A FEW EXCEPTIONS!!! »H only needs 2 electrons » Be only needs 4 electrons »B only needs 6 electrons 15 Covalent Bonds and Lewis Structures Most covalent bonds involve the sharing of: – 2 electrons (single covalent bond), – 4 electrons (double covalent bond, or – 6 electrons (triple covalent bond). 16 Covalent Bonds and Lewis Structures We are going to use the N.A.S method: N = needed A = available S = shared (or halogens) H 1 O 2 N 3 C 4 # of bonds * * Element that form the most bonds goes in the middle 17 Covalent Bonds and Lewis Structures O 2: N = 2 (8) A= 6+6 S = 16 – 12 18 = 16 = 12 = 4 (2 bonds) Covalent Bonds and Lewis Structures CO: N= 8+8 A= 4+6 S = 16 – 10 19 = 16 = 10 = 6 (3 bonds) 20 Lewis structures (electron dot structures) show the structure of molecules. (Bonds can be shown with dots for electrons, or with dashes: 1 dash = 2 electrons) H2 CCl4 N2 HBr 21 Lewis structures (electron dot structures) show the structure of molecules. (Bonds can be shown with dots for electrons, or with dashes: 1 dash = 2 electrons) H2 CCl4 N2 HBr 22 Lewis structures (electron dot structures) show the structure of molecules. (Bonds can be shown with dots for electrons, or with dashes: 1 dash = 2 electrons) H2 CCl4 N2 HBr 23 Lewis structures (electron dot structures) show the structure of molecules. (Bonds can be shown with dots for electrons, or with dashes: 1 dash = 2 electrons) H2 CCl4 N2 HBr 24 Lewis structures (electron dot structures) show the structure of molecules. (Bonds can be shown with dots for electrons, or with dashes: 1 dash = 2 electrons) H2 CCl4 N2 HBr 25 Lewis structures (electron dot structures) show the structure of molecules. (Bonds can be shown with dots for electrons, or with dashes: 1 dash = 2 electrons) H2 CCl4 N2 HBr Covalent Bonds and Lewis Structures - NO3 : N = 8 + 3 (8) A = 5 + 3 (6) + 1 S = 32 – 24 26 = 32 = 24 = 8 (4 bonds)
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