chap 10 full - CHEM 1A03: Intro. Chemistry I...

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1 CHEM 1A03: Intro. Chemistry I Essential Elements: Chemistry, Life & Health Ch.10: Chemical Bonding Department of 1 Chemistry Bonding • Involves transfer or sharing of outer electrons, usually to acquire a stable configuration (Lewis) Ionic bonding Department of 2 Chemistry Na [Ne]3s 1 becomes Na + [Ne] and Cl [Ne]3s 2 3p 5 becomes Cl [Ar] ( transfer of electrons) p. 374 Covalent Bonding • Covalent bonding Sharing of electrons – Often to attain an octet of electrons – Often between 2 non-metals Department of 3 Chemistry – Lewis structure shows all electrons as equivalent Coordinate covalent bond – One atom provides both e for a bond – e.g. NH 3 + H + NH 4 + p. 375-377 Electronegativity (EN) – Fig. 10-6 Department of 4 Chemistry • Atom’s ability to compete for e in a bond • Trend: EN increases across a period and up a group • Pauling scale: F 4.0 (highest EN) p. 381-382 Bond Polarity Polar covalent bonds Unequal sharing of e – Indicated by polar arrow and partial charges • Dictated by Δ EN between atoms δ + δ - HC l Department of 5 Chemistry Δ EN Bonding Example Large Ionic NaCl Intermediate Polar Covalent PCl 5 Zero (Small) Covalent Cl 2 • Percent ionic character of a bond involving a certain element (e.g. Cl) decreases across a period p. 378-380 Percent ionic character vs. Δ EN Please note this i lik l t t Department of 6 Chemistry 0.4 1.9 Approximately: 0 0.4 Covalent (weakly polar covalent) 0.4 1.9 Polar covalent; > 1.9 Ionic Fig. 10-7 is likely meant to be CsF, not CaF. p. 382
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2 Electrostatic potential maps: Fig. 10-5 NaCl Department of 7 Chemistry HCl Cl 2 Effect of EN on charge distribution p. 380 Lewis Structures • Show bonding (b) and non-bonding (nb) e , and formal charges Department of 8 Chemistry • Octet can be achieved by combination of bonding and nonbonding e • Bonding e can be single, double, triple bonds p. 384 Drawing Lewis Structures 1. Count total # of e (include charge) Add e for negative charge, subtract e for positive charge 2. Draw skeletal structure (central & terminal atoms) H and F are always terminal Department of 9 Chemistry 3. Deduct 2 e for each single bond of skeleton 4. Use remaining e to complete octet of terminal atoms Only 2 e for H 5. Subtract e used for terminal octets 6. If e remain, place on central atom p. 385-388 Drawing Lewis Structures…continued 7. Do all atoms have octet (2 for H)?
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This note was uploaded on 04/03/2010 for the course CHEMISTRY Chem 1A03 taught by Professor Lock during the Spring '02 term at McMaster University.

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chap 10 full - CHEM 1A03: Intro. Chemistry I...

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