《大学化学 Chemistry》课程PPT教学课件（英文）Chapter 6 Chemical bonding and molecular shapes Chapter 7 Molecular Mixing

Chapter 6 Chemical bonding ana molecular shapes How atoms connect to one another?

Chapter 6 Chemical bonding and molecular shapes How atoms connect to one another?

6.1 An atomic model is needed to understand how atoms bond Electrons in the outermost occupied shell of any atom are responsible for the atom's chemical properties The electrons that participate in chemical bonding are called valence electrons (价电子) the shell they occupy is called the valence shell(价层) of an atom Valence electrons can be conveniently represented as a series of dots surrounding an atomic symbol (Electron-dot structure or Lewis dot symbol) Valance electrons can be either paired or unpaired Paired electrons usually do not form chemical bonds with other elements

6.1 An atomic model is needed to understand how atoms bond Electrons in the outermost occupied shell of any atom are responsible for the atom’s chemical properties. The electrons that participate in chemical bonding are called valence electrons (价电 子),the shell they occupy is called the valence shell (价层) of an atom. Valence electrons can be conveniently represented as a series of dots surrounding an atomic symbol. (Electron-dot structure or Lewis dot symbol). Valance electrons can be either paired or unpaired. Paired electrons usually do not form chemical bonds with other elements

Unpaired Unpaired electrons Paired electron electrons CI C Chlorine Carbon 1A 8A 1314151617 H 3A 4A 5A 6a 7A He: NaMq3456789101112 Al··SI 3B 4B 5B 6B 7B 8B 1B 2B K As. Se b·sr· In. Sr n Cs.B FrRa·

• • • • Cl • • • C • • •• Unpaired electrons Unpaired electron Paired electrons Chlorine Carbon

6.2 Atoms can lose or gain electrons to become ions(离子 Na 11 protons When the number of protons in the 11 electrons nucleus of an atom equals to the number of electrons in the atom the charges balance and the atom Nat 11 protons is electrically neutral. If one or 10 electrons more electrons are lost or gained the atom takes on a net electric charge. Any atom having a net electric charge is called an ion. If C 17 protons 17 electrons the electrons are lost the ion's net charge is positive. If the electrons are gained, the ions net charge is 17 protons negative Cl electrons

6.2 Atoms can lose or gain electrons to become ions (离子) When the number of protons in the nucleus of an atom equals to the number of electrons in the atom, the charges balance and the atom is electrically neutral. If one or more electrons are lost or gained, the atom takes on a net electric charge. Any atom having a net electric charge is called an ion. If the electrons are lost, the ion’s net charge is positive. If the electrons are gained, the ion’s net charge is negative. Na 11 protons 11 electrons Na+ 11 protons 10 electrons Cl 17 protons 17 electrons Cl- 17 protons 18 electrons

Shell model can be used to deduce the type of ion an atom tends to form atoms tend to lose or gain electrons so that they end up with an outermost occupied shell that is filled to capacity 1A 1314151617 1092A 3A4A5A6A7A400 6941901218 1201140601594189s42017 3456789101112 3B 4B 5B 6B 7B 1B 2B 28.0555309738320435452739.948 20212223 28 9s340m4945591551951549158975932569364569723m2n921678%79048380 Rb Sr Y ir Nb Mo/Tc/4 454448 Ru RI h Pd A gCd In Sn Sb Te IXe s5467887628909921|9969594∞910.m1120106421 7868 11211 11481s 118710121.757112760169041129 Hf Ta w Re Os Ir Pt Au Hg TI PbBi 132905137x2196178491809183841835719023192219508195%672092043852m220980 200(22 r RaAc‖ Rf Db Sg Bh HsM 2)220232702510261)c262c63(262c2659c26cccr

Shell model can be used to deduce the type of ion an atom tends to form: Atoms tend to lose or gain electrons so that they end up with an outermost occupied shell that is filled to capacity. 1+ 2+ 3+ 4- 3- 2- 1- 0

6.3 Ionic bonds result from a transfer of electrons When an atom that tends to lose electrons is placed in contact with an atom that tends to gain them, the result is that an electron transfer and the formation of two oppositely charged ions. The two oppositely charged ions are thus attracted to each other by the electric force, which holds them together Na+ (anton This electric force of attraction between two oppositely charged ions is called an ionic bond(离子键) All compounds containing ions are referred to as ionic compounds(a 子化合物)

6.3 Ionic bonds result from a transfer of electrons When an atom that tends to lose electrons is placed in contact with an atom that tends to gain them, the result is that an electron transfer and the formation of two oppositely charged ions. The two oppositely charged ions are thus attracted to each other by the electric force, which holds them together. This electric force of attraction between two oppositely charged ions is called an ionic bonds (离子键). All compounds containing ions are referred to as ionic compounds (离 子化合物)

How to judge the composition ofan ionic compound? Balance ofelectric charge lonic bonds formed Aluminum oxide, Al,O, Rub rehire

How to judge the composition of an ionic compound? Balance of electric charge Ruby Sapphire

6. 4 Covalent bonds result from a sharing ofelectrons The electrical attraction in which atoms are hold ●● F together by their mutual FF attraction for shared 7e 7e 8e 8e electrons is called an covalent bond(共价键)A compound composed of atoms held together by oo 0一H H covalent bonds is a H. covalent compound(共价 化合物)

6.4 Covalent bonds result from a sharing of electrons The electrical attraction in which atoms are hold together by their mutual attraction for shared electrons is called an covalent bond (共价键). A compound composed of atoms held together by covalent bonds is a covalent compound (共价 化合物). F + F 7e- 7e￾F F 8e- 8e-

More than one electron can be shared in an atom double bond(双键) and triple bond(叁键) 03883:0 :N::N: single covalent bond 0=C=0 ●N≡N double bonds triple bond

More than one electron can be shared in an atom: double bond (双键) and triple bond (叁键). O C O double bonds N N triple bond F F single covalent bond

6.5 Valence electrons determine molecular shape How to determine the three a HB-H O=C=0 dimensional structure of a covalent compound? H Valence shell electron-pair repulsion(vEsPr) any H-H given pair of valence shell electrons strives to get as far away as possible from all other electron pairs in the hell

6.5 Valence electrons determine molecular shape How to determine the three dimensional structure of a covalent compound? Valence shell electron-pair repulsion (VESPR): any given pair of valence￾shell electrons strives to get as far away as possible from all other electron pairs in the shell