Chapter 6 Chemical bonding and 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 atoms 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 alence 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 Paired electron electrons electrons CI Chlorine Carbon 18 1A 8A 2 1314151617 2A 3A 4A 5A 6A 7A He LI-B B E Wg3456789101112A,s,,§·c, 3B 4B 5B 6B 7B 8B. 18 2B K- Ca Ga..Se.·,i b·Sr in·sn .Cs- Ba .TI.Pb.Bi.-Po: At. Fr-Ra
• • • • Cl • • • C • • •• Unpaired electrons Unpaired electron Paired electrons Chlorine Carbon
6.2 Atoms can lose or gain electrons to become ions(离力 Na 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 7 protons negative Cl 18 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 illed to capacity 1+2+ |+|2- 18 1314151617 1002A 3A 4A 5A 6A 7A 108111201114071599418942017 3456789101112 29403B4B5B6B7B 3093832063452739948 192021 25262728293031 333435 T2排石 V Cr Mn Fe Ce Se Br Kr 39340844948095519013493915584718.931560365653697237261|7492 799048380 38 sN阳 515253 Ib Mo TcR X s546786289992499064s9e9101m1029061042ms8ma14ss170117s711276126019 La Hf Tar Ir Pt Au Hg TI PbBiPo 13290513x2139617809180961838418627190251922195061%%6720920402m72208902010)(2 Fr Ac Rf Db Sg HsMI 2701061c62636259ccm2)cz2 89
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 lonic 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+ tenton This electric force of attraction between two oppositely charged ions is called an ionic ions are referred to as ionic compounds(4 1 y bons(离子键) All compounds containing 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 of an ionic compound? Balance of electric charge lonic bonds formed Aluminum oxide, Alz O3 Ruby Sapphire
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°)+(F together by their mutual attraction fo shared 7e 7e Be 8e electrons is called an covalent bond(共价键)A compound composed of atoms held together by O一H covalent bonds is a HO 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- 7eF F 8e- 8e-
More than one electron can be shared in an atom double bond(双键) and triple bond(叁键) oBs g:o) d 1:N:::N: single covalent bond 乙 O=C=0 N≡N double bonds ple 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 H-ic-H CEo dimensional structure of a covalent compound? Valence shell electron-pair repulsion(vEsPra:any given pair of valence shell electrons strives to get as far away as possible from all other electron pairs in the she
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 valenceshell electrons strives to get as far away as possible from all other electron pairs in the shell