Chapter 4 Compounds and Their Bonds

Chapter 4Compounds and Their Bonds 4.1 Valence Electrons 4.2 Octet Rule and Ions LecturePLUS Timberlake

Chemical Bonds • Attraction between two or more atoms • Interaction between valence electrons • Ionic bonds • Covalent bonds LecturePLUS Timberlake

Valence Electrons • Electrons in the highest (outer) electron level • Have most contact with other atoms • Known as valence electrons • Outer shells of noble gases contain 8 valence electrons (except He = 2) Example: Ne 2, 8 Ar 2, 8, 8 LecturePLUS Timberlake

Electron Dot Structures Symbols of atoms with dots to represent the valence-shell electrons 1A 2A 3A 4A 5A 6A 7A 8A H He:      LiBe B  C  N  O : F :Ne :            Na Mg AlSiPS:Cl  :Ar :     LecturePLUS Timberlake

Learning Check  A. X would be the electron dot formula for 1) Na 2) K 3) Al   B.  X  would be the electron dot formula  1) B 2) N 3) P LecturePLUS Timberlake

Solution  A. X would be the electron dot formula for 1) Na 2) K   B.  X  would be the electron dot formula  2) N 3) P LecturePLUS Timberlake

Octet Rule • An octet in the outer shell makes atoms stable • Electrons are lost, gained or sharedto form an octet • Unpaired valence electrons strongly influence bonding LecturePLUS Timberlake

Formation of Ions from Metals • Ionic compounds result when metals react with nonmetals • Metals loseelectrons to match the number of valence electrons of their nearest noble gas • Positive ionsform when the number of electrons are less than the number of protons Group 1A metals ion 1+ Group 2A metals ion 2+ • Group 3A metals ion 3+ LecturePLUS Timberlake

Formation of Sodium Ion Sodium atom Sodium ion Na  – e Na + 2-8-1 2-8 ( = Ne) 11 p+ 11 p+ 11 e- 10 e- 01+ LecturePLUS Timberlake

Formation of Magnesium Ion Magnesium atom Magnesium ion  Mg  – 2e Mg2+ 2-8-2 2-8 (=Ne) 12 p+ 12 p+ 12 e- 10 e- 0 2+ LecturePLUS Timberlake

Some Typical Ions with Positive Charges (Cations) Group 1A Group 2A Group 3A H+ Mg2+ Al3+ Li+ Ca2+ Na+ Sr2+ K+ Ba2+ LecturePLUS Timberlake

Learning Check A. Number of valence electrons in aluminum 1) 1 e- 2) 2 e- 3) 3 e- B. Change in electrons for octet 1) lose 3e- 2) gain 3 e- 3) gain 5 e- C. Ionic charge of aluminum 1) 3- 2) 5- 3) 3+ LecturePLUS Timberlake

Solution A. Number of valence electrons in aluminum 3) 3 e- B. Change in electrons for octet 1) lose 3e- C. Ionic charge of aluminum 3) 3+ LecturePLUS Timberlake

Learning Check Give the ionic charge for each of the following: A. 12 p+ and 10 e- 1) 0 2) 2+ 3) 2- B. 50p+ and 46 e- 1) 2+ 2) 4+ 3) 4- C. 15 p+ and 18e- 2) 3+ 2) 3- 3) 5- LecturePLUS Timberlake

Solution Give the ionic charge for each of the following: A. 12 p+ and 10 e- 2) 2+ B. 50p+ and 46 e- 2) 4+ C. 15 p+ and 18e- 2) 3- LecturePLUS Timberlake

Learning Check A. Why does Ca form a Ca2+ ion? B. Why does O form O2- ion? LecturePLUS Timberlake

Solution A. Why does Ca form a Ca2+ ion? Loses 2 electrons to give octet 2-8-8-2 2-8-8 (like Ar) B. Why does O form O2- ion? Gains 2 electrons to give octet 2-6 + 2e- 2-8 (like Ne) LecturePLUS Timberlake

Ions from Nonmetal Ions • In ionic compounds, nonmetals in 5A, 6A, and 7A gain electrons from metals • Nonmetal add electrons to achieve the octet arrangement • Nonmetal ionic charge: 3-, 2-, or 1- LecturePLUS Timberlake

Fluoride Ion unpaired electron octet 1 - : F  + e: F :  2-7 2-8 (= Ne) 9 p+ 9 p+ 9 e- 10 e- 0 1 - ionic charge LecturePLUS Timberlake

Learning Check Complete the names of the following ions: 5A 6A 7A N3 O2 F nitride __________ fluoride P3 S2 Cl ___________ __________ _________ Br  _________ LecturePLUS Timberlake

Solution 5A 6A 7A N3 O2 F nitride oxide fluoride P3 S2 Cl phosphidesulfidechloride Br  bromide LecturePLUS Timberlake

Chapter 4 Compounds and Their Bonds