Chapter 5 Chemical Bonds, Nomenclature, Lewis Structure and Molecular Shapes
75% % Ionic Character 50% 25% Electronegativity difference
I. Chemical Bonds B. Ionic Bonds • Know: Metals combine with nonmetals & form ionic bonds by losing or gaining electrons to mimic closest Inert Gas (VIIIA). IA - Na, K, Li, etc become +1 ions: Na+ IIA - Ca, Mg, etc become +2 ions: Ca+2 IIIA - Al, Ga become +3 ions: Al+3 VA - N, P become -3 ions: N-3 VIA - O, S become -2 ions: O-2 VIIA - F, Cl, Br, I become -1 ions: F-1 • Opposite ions attract in a ratio so that the product is neutral. Inert Gas e- Configurations
I. Chemical Bonds B. Ionic Bonds Example Do not show charges in final formula. NaCl NOT Na+Cl-
I. Chemical Bonds B. Ionic Bonds -Examples Na+ + Na+ + O-2Na2O Ca+2+F- + F-CaF2 Mg+2 + S-2 MgS Al+3 + Al+3 + O-2 + O-2 + O-2 Al2O3 Give the formulas for the following: Na & Br Ca & O Ba & I Li & O Al & F Mg & N Many transition metals form ionic bonds & can have several charges such as Fe+2 = Iron (II)Fe+3 = Iron (III). Do not need to know these.
I. Chemical Bonds C. Electron Dot (Lewis) Strucures - A Lewis electron dot structure is a symbol in which the valence electrons are shown as dots. - Examples: Na. Mg: Na+ Ca2+ H:1- (Called Hydride) :C: :Si: - How many valence electrons (dots) would N3- O2- F- or Ne have? What about Mg+2?
II. Covalent Bonds A. Introduction EN = electronegativity - Definition of a covalent bond: A bond formed by the sharing of two electrons. • When two atoms of similar EN combine, neither has the “pull” to take electrons away & a sharing of electrons results. • This occurs when NONMETALS combine with NONMETALS.Note: H is a nonmetal. • Example: H. + H. ---) H—H = H2 - The atoms share valence electrons to get stable group VIIIA e- configurations.
II. Covalent Bonds A. Introduction • Covalent bond = sharing of 2 electrons. • 2 shared electrons with (Single Bond). • 4 shared electrons with (Double Bond). • 6 shared electrons with (Triple Bond). • We frequently show the structure as a Lewis Structure - covalent bonds with lines and nonbonding valence electrons as dots. - Note: Group IVA usually forms 4 bonds; VA three bonds; VIA two bonds; and VIIA (along with H) one bond.
II. Covalent Bonds B. Examples H. + F::: ---) H F::: H. + O + .H ---) H O H :N + N: ---) :N N: :::Cl. + .O. + .Cl::: ---) :::Cl O Cl::: ::O: + :C: + :O:: -----) ::O = C = O::
II. Covalent Bonds C. Lewis Structures 2. Examples H I H2O NH4+ H2O2 CH4 SO2 AlCl4- NO2- CN-
Bonding SummaryTwo General Bonding Types • Ionic: Compound containing metallic element. Atoms lose/gain e to look like nearest inert gas. Add together ions such that neutralize charge. Ia IIa IIIa Va VIa VIIa +1 +2 +3 -3 -2 -1 2. Covalent: Compound containing nonmetals. Atoms obtain inert gas configuration by sharing valence electrons. : :: :::