1. H2 = H H H H H H STEP 1 STEP 2 REGENTS REVIEW,MAY 31, JUNE 1,2 2008
CHEM
IS FUN
REGENTS REVIEW,MAY 31, JUNE 1,2 2008
CAIAFA
DRAW THE DOT STRUCTURES OF H2,O2,N2,Cl2,Br2,I2,F2 .
   1)How would you estimate the relative melting and boiling points of these?
   2)Put them in ascending boiling point order and indicate how you do this.
    3)Indicate the type of molecule and type of bond.
   4)List the characteristics and explain them with the bonding and type of attraction.
THIS H SHARES THE 2 ELECTRONS IT NEEDS, IT NOW HAS THE CONFIGURATIONOF He:
THIS H SHARES THE 2 ELECTRONS IT NEEDS, H IS NOT AN OCTET ELEMENT D.
STEP 1 H2 H H H H
STEP 2 H H =
THE IONIC CHARACTER IS 0.0, THE BOND IS NON-POLAR COVALENT
DRAW LEWIS VALENCE DOT STRUCTURE, CONNECT ONLY SINGLE ELECTRONS
DRAW LEWIS VALENCE DOT STRUCTURE, EACH ELECTRON PAIR IS A DASH-LINE!
DRAW LEWIS VALENCE DOT STRUCTURE, EACH SINGLE BOND IS 2 e-

2. VSEPR (valence shell electron pair repulsion)
Gives geometry to assess polarity etc.
Assume central atom is LEAST electronegative.
Hydrogen cannot be the central atom as it makes only one bond.
UNBONDED e-PAIRS ON CENTRAL ATOM
BONDS ON CENTRAL ATOM
GEOMETRY
EXAMPLES 4
TETRAHEDRAL
CH4 1 3
PYRAMIDAL
NH3 2
BENT
(V SHAPE)
H2O
NO CENTRAL, ONLY 2 ATOMS
1(in molecule)
LINEAR H2
TRIGONAL PLANAR
BF3

3. D.
STEP 1 O O
STEP 2 O O O O O2
EACH O SHARES THE 4 e-(DOUBLE BOND) ELECTRONS IT NEEDS, IT NOW HAS THE OCTET CONFIGURATION OF NEON
DRAW LEWIS VALENCE DOT STRUCTURE, CONNECT ONLY SINGLE ELECTRONS, 2 FOR EACH OXYGEN Ne
Important: ALL OF THIS SERIES (H2,O2,N2,Cl2,Br2,I2,F2 ) ARE NON POLAR FOR THE FOLLOWING REASONS:
THEY HAVE IONIC CHARACTER OF 0.0
THEY ARE LINEAR (SYMMETRICAL) – ONE BOND
THE BONDS ARE NON POLAR.
ALL (EXCEPT I AND Br) ARE GASSES AT STP.
ALL ARE ELEMENTAL MOLECULAES, OXIDATION STATE 0!

4. N N
STEP 1 N N
STEP 2 N N
The electron configuration of nonmetals will resemble the noble gas of their own period
Connect only single electrons for covalent (molecular) substances.
Each nitrogen has an octet, isoelectronic to Ne
Each nitrogen shares 6 electrons, triple bond.
RELATIVE ASCENDING BOILING AND MELTING SERIES
H2(2g/mol), O2(32), N2(28), Cl2(70), Br2(161), I2(254), F2(38)
H2(2g/mol), N2(28), O2(32), F2(38), Cl2(70), Br2(161), I2(254)
Solid at STP
Liquid at STP
1-LOWEST 2 3 4 5 6
7-HIGHEST
Van der Waals increase with molar mass (gfm), use gfm for nonpolar

5. H H H O H O H O H Ne IONIC CHARACTER = 2.1 – 3.5 = 1.4 , POLAR COV.
DRAW THE DOT STRUCTURES FOR H2O, H2S, SiO2, CO2, CCl3F, CH4, HF.
a.     -WHICH AR POLAR, WHICH ARE NOT.
b.     -INDICATE THE TYPE OF BOND AND THE TYPE OF MOLECULE FOR EACH.
c.      -PUT IN ASCENDING BOILING POINTS, INDICATE HOW YOU SO THIS.
d.     -List the characteristics of each and explain why.
IONIC CHARACTER
= 2.1 – 3.5 = 1.4 , POLAR COV. H H H O H O
STEP 2 H O H
STEP 1
Next
slide
Connect single electrons
Each H shares the 2 e- achieve He: configuration
O shares the 8 e- achieve Ne configuration Ne

6. H O H
WITH 2 BONDS AND 2 UNSHARED PAIRS OF e-, THE GEOMETRY IS BENT. H H
THE BONDING IS CORRECT, BUT THE GEOMETRY IS NOT! O
YELLOW ARROWS ARE BOND POLARITY VECTORS, PONT TO MOST ELECTRONEGATIVE ELEMENT, NEGATIVE POLE.
THE LEAST ELECTRONEGATIVE ATOM IS THE POSITIVE POLE AND GETS THIS POSITIVE POLE SYMBOL + + H H +
THE MOST ELECTRONEGATIVE ATOM IS THE NEGATIVE POLE AND GETE THIS NEGATIVE POLE SYMBOL O
THE 2 YELLOW VECTOR ARROWS ADD UP TO THIS BIG ONE, WHICH REPRESENTS MOLECULAR
POLARITY, POINTS TO NEGATIVE POLE. - -

7. H H H H O S + + + + - - IONIC CHARACTER(EACH BOND)
=| 2.1 – 2.6| = 0.5 , WEAKLY POLAR COVALENT. + + + + H H H H O S = - -
MOLECULAR POLARITY
INCREASES
(IF ASSYMETRICAL)
AS IONIC CHARACTER INCREASES
BOND POLARITY
INCREASES
causes
causes
WATER IS MORE POLAR
HAS HIGHER MELTING AND BOILING POINTS
H2O HAS GREATER IONIC CARACTER THAN H2S
H2O HAS GREATER BOND POLARITY THAN H2S
causes
causes

8. d Si O O Si O O Si SI O Si O STEP 1 STEP 2
EACH THE Si HAS SHARED 4 e- TO ACHIEVE AN OCTET O Si O O
Note: THE Si IS HYBRID, NOT GROUND STATE. Si SI
EACH OXYGEN HAS SHARED 4 e- TO ACHIEVE AN OCTET
IONIC CHARACTER
= |3.5 – 1.9| = 1.6, STRONGLY POLAR COV.
STEP 2 O Si O
SiO2 (silicon dioxide) is NONPOLAR , it is LINEAR ( 2 bonds) and symmetrical. The BONDS ARE polar but the molecule is not!
NOTICE THE VECTOR ARROWS CANCEL = 0

9. IONIC CHARACTER(EACH BOND)
=| 2.1 – 2.6| = 0.5 , WEAKLY POLAR COV. O C O
CO2 (carbon dioxide) is NONPOLAR , it is LINEAR
( 2 bonds) and symmetrical. The BONDS ARE polar but the molecule is not! = 0.0
NOTICE THE VECTOR ARROWS CANCEL
Note: THE C IS HYBRID, NOT GROUND STATE. C + H H H C F + - H C H H H +
POLAR BONDS,SYMMETRICAL NON POLAR MOLLECULE
POLAR BONDS,
A-SYMMETRICAL POLAR MOLLECULE

10. - [ [ - [ [ Mg + Cl Mg +2 Cl Cl Cl MgCl2 Mg2+ Cl1- IONIC CHARACTER
Note: Mg+ 2 has a Ne electron configuration. Mg + Cl
Mg +2
STEP 1 - [ [ Cl
The electron configuration of metals will resemble the noble gas of the period before the period of the metal Cl - [ [ Cl
Mg IS AN ACTIVE METAL THAT NEEDS TO LOSE 2 e-
Cl IS AN ACTIVE NON-METAL THAT NEEDS TO GAIN 1 e-
Note: Cl- has an Ar electron configuration.
MgCl2
Mg2+ Cl1-

11. Al3+ F1- AlF3 CHARACTERISTICS OF IONIC SOLIDS
Form crystal lattice solid with very strong electrostatic attractions between ions.
Ions are fixed in place, rendering the crystal non-conductive, brittle and hard.
The electrons cannot leave the ions, cannot conduct.
The strong electrostatic attractions make it difficult to separate the ions, and this requires great amounts of energy, thus the melting and boiling points are very high.
CHARACTERISTICS OF IONIC liquids and solutions (aq)
Soluble ionic compounds (table F) form conductive solutions mobile ions.
The melt of an ionic substance is always conductive.
Remember: FOR CONDUCTIVITY – MUST HAVE MOBILITY! (OF IONS OR ELECTRONS)

12. CARBON DIOXIDE O C O
EACH OXYGEN HAS 2 SINGLE ELECTRONS, NEEDS TO SHARE TWO MORE FOR AN OCTET, AND TO RESEMBLE NEON.
EACH HYBRID CARBON HAS 4 SINGLE ELECTRONS, NEEDS TO SHARE FOUR MORE FOR AN OCTET, AND TO RESEMBLE NEON.

13. C O CARBON DIOXIDE, VENN DIAGRAM
THE YELLOW CIRCLE REPRESENTS THE OXYGEN”SET” WITH AN OCTET
THE GREEN INTERSECTION AREAS REPRESENT THE 4 SHARED ELECTRONS OF A DOUBLE BOND
THE BLUE CIRCLE REPRESENTS THE CARBON”SET” WITH AN OCTET

14. CARBON DIOXIDE, VENN DIAGRAM CHARACTER OF 0.9, WHICH IS CONALENT POLAR
CO2 HAS AN IONIC
CHARACTER OF 0.9, WHICH IS CONALENT POLAR
AS WIH ALL COVALENT COMPOUNDS, CO2 HAS WEAK ATTRACTIONS, LOW M.P. AND B.P.AND IS NEVER CONDUCTIVE.
EACH DOUBLE BOND IS 4 SHARED ELECTRONS, IS SHORTER AND STRONGER THAN THE SINGLE BOND.

15. Covalent bonds are formed by sharing at least one pair of electrons.
Every covalent bond has a characteristic length that leads to maximum stability.
This is the bond length.

16. Energy required to break a covalent bond in an isolated gaseous molecule is called the bond dissociation energy.