12U Chemistry

Unit 1 Review

 

1.         Electron Configurations

 

            a) lightest halogen: F 1s22s22p6

                b) alkali metal with 2p and 3p electrons: K 1s22s22p63s23p64s1

            c) lightest alkaline  earth metal: Be 1s22s2

            d) non-metallic elements group 14:        C 1s22s22p4

                                                                                                Si [Ne] 3s23p4

2.         Which has Larger Radius

           

            a) Mg or Na     :           Na : lower ENC then Mg, therefore larger radius.

            b) Na or Na+    :           Na : electrons in 3s orbital, Na+ electrons only in 2p orbital.

            c) Cl or Cl-       :           Cl- : adding an e- increases repulsive forces so ion is larger than neutral atom

 

3. I.E. :  energy required to remove an electron from an isolated atom in the gaseous state

            -energy put in \endothermic

 

4. CO2              4+12 = 16 – 4 = 12 -12 = 0                     O = C = O                    linear, Non-Polar

 


                    2p     ___ ___ ___                                                2p                     ___ ___

            C:     2s     ___                                      CO2:     2sp       ___ ___

 

 

 

IF6+                  49 – 1 = 48 – 12 = 36 – 36 = 0

 

                        F                                 

            F                      F                  5d             ___ ___ ___ ___ ___

                        I                       I:      5p   ___ ___ ___

            F                      F                  5s ___

                        F

Octahedral

                                               

                                    IF6+:             5d                        ___ ___ ___

 

  5sp3d2 ___ ___ ___ ___ ___ ___

 

IF+6 is a charged particle so it is automatically polar (it is so polar it is ionic)

 

SnCl5-   4 + 35 + 1 = 40 – 10 =30 – 30 = 0          Trigonal Bipyramidal                 

 

                         Cl

            Cl                     Cl                     5d                ___ ___ ___ ___ ___

                        Sn                    Sn:        5p          ___ ___ ___

                                                            5s    ___

            Cl                     Cl

 

                                                           

5d                     ___ ___ ___ ___

SnCl5-:

        5sp3d   ___ ___ ___ ___ ___

 

SnCl5 -1 is a charged particle so it is automatically polar (it is so polar it is ionic)

 

 

GeF4                 4 + 28 = 32 – 8 = 24 – 24 = 0                 Tetrahedral                   Non-polar

 

 

 

 

F

             |

F          Ge        F

             |

            F

 

 

 

 

 

5)

a)NH3 BP: -33◦C, trigonal pyramidal               CH4 BP: -164◦C, tetrahedral

NH3 is a polar molecule with H-bonding occurring between molecules. This strong IMF allows for a high BP for NH3. CH4 is non-polar with weak London forces between molecules. This results in a lower BP.

 

b) C2H6 (gas)    C6H14 (liquid) at 25◦C, 1Atm

C6H14 is a larger molecule with longer surface area. Therefore it has more London forces between molecules. This stronger IMF allows C6H14 to be a liquid at RT while the smaller C2H6 is a gas.

 

c)Si (MP 1410°C) and Cl2 (MP -101°C): Silicon is a network crystalline solid, covalently bonded to itself. A very high MP is required to melt or break the bonds. Cl2 is a nonpolar molecule with only London forces between molecules. Little energy is required to separate molecules therefore a lower MP.

 

d)MgO (MP 2852°C) and NaF (MP 993°C). Although both are ionic solids, MgO is held by a +2/-2 force of attraction vs +1/-1 force of attraction in NaF.

 

6.         C2O4: resonance structures:

7.   NaBr: c            V: a                  P2O5: b             SiO2: d