CHEMISTRY 20 CHEMICAL BONDING Molecular Bonding Morning Assignment

CHEMISTRY 20 CHEMICAL BONDING Molecular Bonding

Morning Assignment What are 3 characteristics of an ionic bond? How are Molecular Compounds named?

Naming Molecular (Covalent) Compounds The name simply communicates the number of atoms of each element in the compound. � Eg. CS 2 = carbon disulfide Why are covalent bonds named this way? � Ionic compounds are only possible in one ratio because of charges. � Molecular compounds can form with the same ratios even though they are different compounds. � Eg. C 2 H 2 (g) dicarbon dihydride (acetylene) � Eg. C 6 H 6 (l) hexacarbon hexahydride (benzene) � Ratio of both is 1: 1 but they are different

Covalent Bonding Normally forms between 2 non-metals Can happen between two metals � called metallic bonding

Covalent Bonds = Shared Electron(s) Why? � The elctronegativity difference between the two involved atoms is close enough that one does not win the electron battle outright (no transfer) � In non-metals, electronegativity is strong so they both want the electrons. This makes the bond fairly strong

Metallic Bonding = weak bonds The electrons are still shared in metallic bonding, but metals have low electronegativities meaning neither metal has a strong hold on the electron. So valence electrons are free to move about between atoms in no set orbit Electrons act like glue to hold the metal together because of attractive forces to the positive nuclei This mobility of electrons means there is not much structure to the layout of the bonds causing metals to be: � Flexible, Malleable, and ductile This is also why metals are good conductors

Molecular Elements that are diatomic (O 2 (g), N 2 (g), H 2 (g)) and Halogens (I 2 (s), Br 2 (l), Cl 2 (g), F 2 (g)) can be explained by use of covalent bonding � Each Cl atom has 7 valence electrons – correct? � So it needs one more e- to become a stable bond � How could this happen � Through Ionic bonding with Na or another metal, or � Covalently bonding with another Cl If they share valence elctrons then they both have full outer levels

What about others … What about Oxygen with 6 valence electrons � Show Lewis dot diagram � Called a double bond when a pair of electrons are shared What about Nitrogen with 5 valence electrons � Same except with a triple bond � Show Lewis dot diagram

Assignment Reading � Text pages 85 -87 Questions � Text Page 84 #’s � Text Page 86 #’s � Text Page 89 # 2, 7, 8, 10 1, 4 5 abc