Chapter 8 - Basic Properties of Bonding

Chapter 8 - Basic Properties of Bonding - Ch 8 Basic...

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Ch 8 Basic Concepts of Chemical Bonding 8.1 Core & Valence Electrons Atoms will gain/lose or share to try to get the electron configuration of a noble gas, or at least a set of completely full or empty set of valence orbitals. These reactions happen between valence electrons: Ionic Bonding: one atom loses electrons while the other gains electrons Covalent Bonding: atoms share electrons These reactions happen between valence electrons: Core electrons: Those electrons within an atom which have the electron configuration of a noble gas AND those electrons filling an inner shell. Valence electrons: those electrons responsible for the bonding (valence) of an element. Eg) Core Valence Lewis Symbol C 1s 2 2s 2 2p 2 S 1s 2 2s 2 2p 6 3s 2 3p 4 Cl 1s 2 2s 2 2p 6 3s 2 3p 5 Na 1s 2 2s 2 2p 6 3s 1 Na . The famous chemist, G.N. Lewis invented a clever and incredibly usefully way to demonstrate bonding using dots to depict the valence electrons. The dots are distributed in an imaginary square around the element symbol. The important part is to distribute the electrons around the atomic symbol, not pairing the electrons until forced to.
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The Octet Rule p2 Since most elements are trying to obtain a noble gas electron configuration, they will be happy when they have 8 electrons around them in the imaginary square. Why 8?? 8.2 Bonding in Ionic This type of bonding occurs between elements that want to lose electrons ( metals ) and elements that want to gain electrons ( non-metals ) or nonmetal polyatomic ions) Eg) 2 Na (s) + Cl 2 (g) Æ 2 NaCl (s) Dot Structures: Energy Involved in Ionic Bonding (see diagram p 308) Na (s) + ½ Cl 2 (g) Æ NaCl (s) Na(s) Æ Na(g) Heat of sublimation of Na endo Na (g) Æ Na + (g) + e - 1 st Ionization Potential Na endo Cl 2 (g) Æ 2 Cl (g) Bond energy of Cl 2 endo Cl (g) + e - Æ Cl- Electron Affinity of Cl exo Na + (g) + Cl - (g) Æ NaCl(s) Crystal Lattice Energy exo Crystal Lattice Energy governed by the equation: E α q1*q2 q = ion charge d d = inter-nuclear distance between ions Higher Crystal Lattice energy from ___________ ion charge and ___________ distance Eg) Which would have a higher crystal lattice energy: NaCl or KI WHY? NaCl or MgO WHY
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8.3 Covalent Bonding p3 When both elements in a prospective bonding pair need to gain electrons, they can do this by SHARING , this is called CO -valent bonding. As two atoms approach each other, the electrons of one atom become attracted to the nucleus of the neighboring atom. As we push them closer the electrons and nuclei begin to repel each other. There exists a distance at which there is a maximum attraction. This is the bond distance. For H
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Chapter 8 - Basic Properties of Bonding - Ch 8 Basic...

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