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This webpage explores chemical bonding in chemistry, focusing on ionic and covalent bonds. Learn about the Octet Rule, Lewis Dot Symbols, and the formation of stable compounds. Discover the principles of electron transfer in ionic bonding (e.g., NaCl) and electron sharing in covalent bonding (e.g., HCl). Explore the Lewis Model of Bonding and concepts such as isoelectronic species. Understand the significance of valence electrons and the role they play in chemical reactivity. Study examples and calculations involving lattice energy in ionic compounds. This resource provides an in-depth look at chemical bonding theories and their application in forming compounds.
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CHEMISTRY 161 Chapter 9 Chemical Bonding I www.chem.hawaii.edu/Bil301/welcome.html
Periodic Table of the Elements ns2np6 ns1 ns2 chemical reactivity - valence electrons
THE OCTET RULE atoms combine to form compounds in an attempt to obtain a stable noble gas electron configuration ns2np6 isoelectronic
A + B → AB 1. ELECTRON FULLY TRANSFERED IONIC BONDING NaCl 2. ELECTRON SHARING COVALENT BONDING HCl
LEWIS MODEL OF BONDING LEWIS DOT SYMBOL DOT represents one valence electron H. Gilbert Lewis (1875-1946)
. . . . . . . . . . with the exception of He, the main group number represents number of ‘dots’
IONIC BONDING Na electron transfer Ne core implied in symbol 1s22s22p63s1 Lewis Symbol
Na Ne core implied in symbol Cl 1s22s22p63s23p5 1s22s22p63s1 Lewis Symbol
IONIC BONDING Cl Cl Na the formation of ionic bonds is represented in terms of Lewis symbols Na+ 1s22s22p63s23p6 1s22s22p6 the loss or gain of electrons(dots) until both species have reached an octet of electrons
Cl Cl [Ne] 3s23p6 represents one orbital (Pauli: 2 electrons)
ions stack together in regular crystalline structures electrostatic interaction ionic solids typically 1. high melting and boiling points 2. brittle 3. form electrolyte solutions if they dissolve in water
Li(s) + ½ F2(g) → LiF(s) enthalpy of formation lattice energy Li+(g) + F-(g) → LiF(s) Hess’s Law enthalpy is a state function Born-Haber Cycle
Li(s) + ½ F2(g) → LiF(s) Li+(g) + F-(g) 5 ΔHoR= ΣΔHoi i=1 ΔHo4 ΔHo3 ΔHo5 Li(g) + F(g) ΔHo2 ΔHo1 ΔHoR LiF(s) Li(s) + ½ F2(g)
Mg(s) + ½ O2(g) → MgO(s) Mg2+(g) + O2-(g) ΔHo6 7 ΔHo5 ΔHoR= ΣΔHoi i=1 Mg+(g) + O-(g) ΔHo7 ΔHo4 ΔHo3 Mg(g) + O(g) ΔHo1 ΔHo2 ΔHoR MgO(s) Mg(s) + ½ O2(g)
SUMMARY Lewis Dot Octett Rule Lattice Energy of Ionic Compounds 600 – 4000 kJmol-1
Homework Chapter 9 pages 329-337, problem sets