CHEM
IS
FUN
REGENTS REVIEW,JUNE 9, 10
CAIAFA-MAY
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
H
D. THE IONIC
CHARACTER
IS 0.0, THE
BOND IS
NON-POLAR
COVALENT
H
STEP 1
DRAW LEWIS
VALENCE DOT
STRUCTURE,
CONNECT ONLY
SINGLE
ELECTRONS
HH
STEP 2
DRAW LEWIS
VALENCE DOT
STRUCTURE,
EACH SINGLE
BOND IS 2 e-
H H = H2
DRAW LEWIS
VALENCE DOT
STRUCTURE,
EACH
ELECTRON
PAIR IS A DASHLINE!
VSEPR (valence shell electron pair repulsion)
1) Gives geometry to assess polarity etc.
2) Assume central atom is LEAST electronegative.
3) Hydrogen cannot be the central atom as it makes only one bond.
UNBONDED ePAIRS ON
CENTRAL ATOM
BONDS ON
CENTRAL ATOM
GEOMETRY
EXAMPLES
0
4
TETRAHEDRAL
CH4
1
3
PYRAMIDAL
NH3
2
2
BENT
(V SHAPE)
H2O
NO CENTRAL,
ONLY 2 ATOMS
1(in molecule)
LINEAR
H2
0
3
TRIGONAL
PLANAR
BF3
O
O
STEP 1
O O
STEP 2
OO
D.
DRAW LEWIS VALENCE
DOT STRUCTURE,
CONNECT ONLY SINGLE
ELECTRONS, 2 FOR EACH
OXYGEN
EACH O SHARES THE 4 e-(DOUBLE
BOND) ELECTRONS IT NEEDS, IT
NOW HAS THE OCTET
CONFIGURATION OF NEON
O2
Ne
Important: ALL OF THIS SERIES (H2,O2,N2,Cl2,Br2,I2,F2 )
ARE NON POLAR FOR THE FOLLOWING REASONS:
1)
2)
3)
4)
5)
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!
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
Each nitrogen shares 6
electrons, triple bond.
Ne
RELATIVE ASCENDING BOILING AND MELTING SERIES
H2(2g/mol), O2(32), N2(28), Cl2(70), Br2(161), I2(254), F2(38)
Liquid
at STP
Solid at
STP
H2(2g/mol), N2(28), O2(32), F2(38), Cl2(70), Br2(161), I2(254)
1-LOWEST
2
3
4
5
6
7-HIGHEST
Van der Waals increase with molar mass (gfm), use gfm for nonpolar
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
O
Connect
single
electrons
H
STEP 1
H O H
Each H shares
the 2 eachieve He:
configuration
STEP 2
O shares the 8
e- achieve Ne
configuration
Ne
H OH
Next
slide
H OH
WITH 2 BONDS AND 2 UNSHARED PAIRS
OF e-, THE GEOMETRY IS BENT.
H
THE BONDING IS
CORRECT, BUT THE
GEOMETRY IS NOT!
H
O
YELLOW ARROWS ARE BOND POLARITY
VECTORS, PONT TO MOST ELECTRONEGATIVE
ELEMENT, NEGATIVE POLE.
+
H
THE MOST ELECTRONEGATIVE
ATOM IS THE NEGATIVE POLE
AND GETE THIS NEGATIVE
POLE SYMBOL
-
+
H
O
-
THE LEAST
ELECTRONEGATIVE ATOM IS
THE POSITIVE POLE AND GETS
THIS POSITIVE POLE SYMBOL
+
THE 2 YELLOW VECTOR
ARROWS ADD UP TO THIS
BIG ONE, WHICH
REPRESENTS MOLECULAR
POLARITY, POINTS TO
NEGATIVE POLE.
+
+
+
+
H
H
H
H
O
S
-
-
AS IONIC
CHARACTER
INCREASES
H2O HAS
GREATER IONIC
CARACTER
THAN H2S
causes
causes
IONIC CHARACTER(EACH BOND)
=| 2.1 – 2.6| = 0.5 , WEAKLY POLAR
COVALENT.
BOND
POLARITY
INCREASES
H2O HAS
GREATER
BOND
POLARITY
THAN H2S
+
causes
=
MOLECULAR
POLARITY
INCREASES
(IF ASSYMETRICAL)
causes
WATER IS
MORE POLAR
HAS HIGHER
MELTING AND
BOILING POINTS
Si
O
STEP 1
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.
EACH THE Si HAS
SHARED 4 e- TO
ACHIEVE AN OCTET
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
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.
H
H C H
H
POLAR BONDS,SYMMETRICAL
NON POLAR MOLLECULE
C
+
+
H
H C F
H
+
-
POLAR BONDS,
A-SYMMETRICAL POLAR
MOLLECULE
+
Cl
Cl
Mg IS AN ACTIVE
METAL THAT
NEEDS TO LOSE 2 e-
STEP 1
Mg +2
The electron configuration of
metals will resemble the noble
gas of the period before the
period of the metal
Cl IS AN ACTIVE
NON-METAL THAT
NEEDS TO GAIN 1 e-
[ Cl
[ Cl
-[
Mg
Note: Mg+ 2 has a Ne
electron configuration.
-[
IONIC CHARACTER
= |1.3 – 3.2| = 1.9 , IONIC
Note: Cl- has a Ne
electron configuration.
Mg2+ Cl1-
MgCl2
Al3+ F1-
AlF3
CHARACTERISTICS OF IONIC SOLIDS
1) Form crystal lattice solid with very strong electrostatic attractions between
ions.
2) Ions are fixed in place, rendering the crystal non-conductive, brittle and hard.
3) The electrons cannot leave the ions, cannot conduct.
4) 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)
1) Soluble ionic compounds (table F) form conductive solutions mobile ions.
2) The melt of an ionic substance is always conductive.
3) Remember: FOR CONDUCTIVITY – MUST HAVE MOBILITY! (OF IONS
OR ELECTRONS)