8 Concepts of Chemical Bonding

8 Concepts of Chemical Bonding - Chapter 8 Concepts of...

Info iconThis preview shows pages 1–6. Sign up to view the full content.

View Full Document Right Arrow Icon
1 Chapter 8 Concepts of Chemical Bonding Chemical Bonds Three basic types of bonds: Ionic: Electrostatic attraction between ions Covalent: Sharing of electrons Metallic: Metal atoms bonded to several other atoms 2
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
2 Ionic Bonding Energetics of Ionic Bonding As we saw in the last chapter, it takes 495 kJ/mol to remove electrons from sodium. We get 349 kJ/mol back by giving electrons to chlorine. But these numbers don’t explain why the reaction of sodium metal and chlorine gas to form sodium chloride is so exothermic! Energetics of Ionic Bonding (cont) What is as yet unaccounted for is the electrostatic attraction between the newly formed sodium cation and chloride anion. 4
Background image of page 2
3 Lattice Energy This third piece of the puzzle is the lattice energy : The energy associated with electrostatic interactions is governed by Coulomb’s law: The energy required to completely separate a mole of a solid ionic compound into its gaseous ions. E el = κ Q 1 Q 2 d Charges of the particules Distance between their centers Proportionality constant (8.99x10 9 jm/C 2 ) Lattice Energy (cont) • Lattice energy, then, increases with the charge on the ions. • It also increases with decreasing size of ions. Table 8.2 6
Background image of page 3

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
4 By accounting for all three energies (ionization energy, electron affinity, and lattice energy), we can get a good idea of the energetics involved in such a process. Fig 8.4 The Born-Haber cycle Energetics of Ionic Bonding Energetics of Ionic Bonding (cont) H 0 f (NaCl) s = - 411 Kj/mol H = - H Lattice H 0 f (NaCl) s = H 0 f (Na) g H 0 f (Cl) g + + I 1 (Na) + E(Cl) - H Lattice H Lattice = 788 Kj/mol Fig 8.4 Na s + 1/2Cl 2(g) NaCl s R o u t e A 8 Na g + Cl - g NaCl s R o u t e B +
Background image of page 4
Octet rule : Elements lose or share electrons to achieve a more stable electron configuration ( isoelectronic with the closest noble gas) . Energetics of Ionic Bonding (cont) These phenomena also helps explain the “octet rule.” Metals, for instance, tend to stop losing electrons once they attain a noble gas configuration. An electron pair that is shared between
Background image of page 5

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Image of page 6
This is the end of the preview. Sign up to access the rest of the document.

This note was uploaded on 04/18/2008 for the course CHEM 121 taught by Professor Wyzlouzil during the Winter '07 term at Ohio State.

Page1 / 21

8 Concepts of Chemical Bonding - Chapter 8 Concepts of...

This preview shows document pages 1 - 6. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online