In August 2002, the French retail giant Carrefour S.A. is considering alternative currencies for raising (euros) EUR750 million in the eurobond market. Carrefour’s investment bankers provide variou...
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In August 2002, the French retail giant Carrefour S.A. is considering alternative currencies for raising (euros) EUR750 million in the eurobond market. Carrefour’s investment bankers provide…Descrição completa
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Chemical Kinetics
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ATOMS ALWAYS UNDERGO CHANGE AND IN DOING SO, THEY COMBINE WITH EACH OTHER, AND HOLD EACH OTHER USING AN INVISIBLE FORCE CALLED A CHEMICAL BOND.
Chemical Bond – invisible force that hold atoms together kinds Results Ionic bond
Forms With formation of ions
E’s are transferred from
a metal to a non metal Covalent bond
Without formation of ions
E’s are shared between
several non metals
Atoms iA Na
Lewis symbol Na
Strength of bond Electrostatic attraction between cation and anion Attraction between the positively charged nucleus and negative electron clouds of the bond; attraction involving the opposite spins of electrons
Formation of Pertinent Bond
Formula
Transfer of electrons
NaCl
1
VIIA Cl Na
Cl
Cl
Transfer of electrons
IIA Ca Ca
+2
-3 Ca3N2
Ca N __ _______________
N
IIIA N
+2
-3
__ __3___ 3________2___ 2______ +6
IA
H
VIIA Cl
LCM= 6
-6
Sharing of electrons HCl
H
H
Cl
Cl
H Cl
IA
H H
IVA
Sharing of electrons
CH4
H H
C
H
C
C
H
In bonding, compound formation,
H
H
C H H
total positive charge = total negative charge Total electropositive charge = total electronegative charge
BOND POLARITY Arises whenever atoms share their electrons electrons unequally that is whenever they have different electronegativities Kinds of chemical bonds Basis of sharing of electrons 1. Non polar ovalent bond – atoms share their electrons equally; atoms have equivalent electronegativities 2. Polar covalent bond- atoms atoms share their electrons non equally; atoms have different different electronegativities Rule :Basis of electronegativity difference (END) If END range is 0 to 0.4
non polar covalent bond
If END range is 0.5 to 1.7 1 .7 to 1.9 – polar covalent bond If END range is >0.5 to 1.7 to 1.9 – ionic bond
THEORIES OF COVALENT BONDING
1. Valence Bond Theory- Atoms contain orbitals ( with spatial spatial orientations and shapes) that will overlap maximally to form covalent bonds 2. Hybridization TheoryHybridization- way of trying to modify the orbital model of an atom to explain the existence of bonds that are equivalent -
Mixing of electrons to form hybrid orbitals
Atoms that show multiple covalency numbers numbers will hybridize Covalency Number – number of unpaired electrons -dictates the number of possible bonds to be formed LEWIS SYMBOL
COVALENCY NUMBER
WILL IT HYBRIDIZE?
1
NUMBER OF FORMED BONDS 1
1
1
NO
4
4
YES
3
3
YES
2
2
YES
NO
H
Cl
C
N
O
Types of Hybrids: Orbitals involved
Number of hybrids
Number of pure orbitals
Name of hybrid
Angle of repulsion among hybrids
Sp3 Sp2
S p p p S p p
4 3
tetrahedral Trigonal planar
109 0 120
sp
S p
2
0 1, (p orbital) 2 (2 p orbitals)
digonal
180
To predict the type of hybrid of an Atom: Guidelines: Single bonds – sp3 Double bonds – sp2 Triple bonds - sp
For Carbon:
If C is bonded to 4 other atoms ; sp3 If C is bonded to 3 other atoms ; sp2 If C is bonded to 2 other atoms ; sp
For N:
If N is bonded to an sp3 C ; sp3 N If N is bonded to an sp2 C; sp2 N If N is bonded to an sp C; sp N
For O
If O is bonded to an sp3 C; sp3 O If O is bonded to an sp2 C; sp2 O
Examples
Angle of repulsion between hybrid and pure orbitals
Steps; 1. determine the skeleton structure of the the m olecule 2. be sure to coun t that that the total number of dots is equal to the total total num ber of valence electrons 3. surround each atom wi th 8 dots; except H, with 2 dots