Download Ch 22 Main Group Chemsitry

1
Lecture 10: Main Group Chemistry
(Chapters 14 and 15)
Trends
1. Within each column (group) the atomic radius tends to increase as we proceed
from top to bottom
2. Within each row (period) the atomic radius tends to decrease as we move from
left to right.
 Orbitals increase in size with increasing principle quantum number, n.
 The effective nuclear charge increases moving from left to right but the
principle quantum number stays the same.
 The effective nuclear charge remains relatively constant while the principle
quantum number increases.
Increasing ionization energy
Decreasing atomic radius
Increasing nonmetallic character and electronegativity
Decreasing metallic character
B
Si
Ge
As
Sb
Te
At
Most metallic element
Increasing
Decreasing
Increasing
Decreasing
metallic
atomic
electronegativity
ionization
radiusenergy
character
Nonmetals
Metals
Most nonmetallic element
Atomic size and bonding
Chapter 22 Main Group Chemistry 1
2
C C
Si
Si
SiO44–
CO2
O
O
C
O
O
4–
Si
O
O
O
HO
HO
P
O
HO
S
OH
O
OH
O
O
Cl
O
HO
formulas of common oxides, oxyanions, hydrides
Group
1A
2A
3A
4A
5A
6A
7A
Common Oxide
M2O
MO
M2O3
AO2
A4O10
AO3
A2O7
Common Hydride
MH
MH2
MH3
AH4
AH3
AH2
AH
+2
+3
+4
+5
+6
+7
BO33–
CO32–
NO3–
SO42–
ClO4–
Highest Oxidation +1
State
Common
Oxyanion
SiO44– PO43–
Chapter 22 Main Group Chemistry 2
3
Valence electrons: ns, np electrons
Group number is the number of valence electrons
ex: Group 7 ns2 np5
7 electrons
Easiest route to octet is add one electron
Ionic Compounds
•
trying to get to a noble gas configuration
Metals (Group 1A, 2A, and 3A) generally form ionic compounds by losing
electrons to form cations
Group 1A form 1+ ions
ex: Na+, K+, Cs+
Group 2A form 2+ ions
ex: Ca2+, Mg2+, Ba2+
Group 3A form 3+ ions
ex: Al3+
Nonmetals
Group 6A and 7A elements will form anions achieve an octet electron
configuration
Group 7A elements will form 1– anions form an octet electron configuration:
F–, Cl–, Br–, I–
Group 6A elements form 2– ions in ionic compounds:
O2-, in MgO
S2- in LiS
Chapter 22 Main Group Chemistry 3
4
Group 7A forms 1- ions in ionic compounds:
F- in NaF
Br- in CaBr2
Cl- in AlCl3
Covalent Compounds
2 non-metals
xs As + F2
As + xs F2
H2O, CH4, CO2, PCl3
AsF3
AsF5
Molecules should have even number of electrons:
ex:
BrF, BrF3, BrF5
NOT BrF2 or BrF4
Exceptions: NO (11 e-), NO2 (17 e-), O2– (13 e-), ClO2 (19 e-)
Naming
ion
acid
Ox. No.
Hypochlorite, ClO–
Hypochlorous, HClO
1+
Chlorite, ClO2–
Chlorous, HClO2
3+
Chlorate, ClO3–
Chloric, HClO3
5+
Perchlorate, ClO4–
Perchloric, HClO4
7+
Fe2+ Ferrous
Fe3+ Ferric
Sn2+ Stannous
Sn4+ Stannic
Chapter 22 Main Group Chemistry 4
5
Chemical Reactions
Combustion in air
 Hydrogen-containing compounds produce H2O
 Carbon-containing compounds produce CO2.
 Nitrogen-containing compounds produce N2.
2CH 3OH(l)  3O2(g)  4H2 O(l)  2CO2 (g)
4CH 3 NH2 (g)  9O2(g)  10H2O(l)  4CO 2(g)  2N2g 
Stability of products: O-H (463 kJ/mol), C=O (799 kJ/mol), and  (941
kJ/mol)
metathesis reaction
Acid-base reactions:
Bronsted-Lowry
Lewis
The weaker the acid, the stronger the conjugate base.
H2, OH–, NH3, CH4
H–, O2–, NH2–, CH3–
CH 3 – (aq)  H2 O(l)  CH 4 (g)  OH  (aq)
NH2 – (aq)  H2O(l)  NH3 (g)  OH  (aq)
Chapter 22 Main Group Chemistry 5
6
Hydrogen "water former"
Isotopes
protium, H
deuterium, D
D2O
tritium
Synthesis Gas
C(s) + H2O(g)

H2(g) + CO(g)
"water gas"
Electrolysis
2 H2O  O2(g) + 4H+ + e2 H2O + 4e-  H2(g) + OH-
Preparing H2 in the lab
1. Metal + Acid  metal salt + H2
Mg(s) + 2 HCl(aq)  MgCl2(aq) + H2(s)
2. Metal + H2O or base  metal hydroxide or oxide + H2
2 Na(s) + 2 H2O(l)  2 NaOH(aq) + H2(g)
2 Fe(s) + 3 H2O(l)  Fe2O3(s) + 3H2(g)
2 Al(s) + 2 KOH(aq) + 6 H2O(l)  2 KAl(OH)4 + 3 H2(g)
3. Metal Hydride + H2O  metal hydroxide + H2
CaH2(s) + 2 H2O(l)  Ca(OH)2(s) + 2 H2(g)
Chapter 22 Main Group Chemistry 6
7
Binary Hydrogen Compounds
Ionic
2Li s  H2 g  2LiH s
Ca s  H2 g  CaH2 s
Hydride
–
H aq  H2Ol  H2g  OH – aq
Metallic - "solutions of hydrogen atoms in metal"
Molecular - formed by nonmetals and semimetals
gases or liquids
H2, HF, H2O, NH3, CH4
Group 8A
Noble gases
He, Ne, K
inert, essentially no chemistry
Helium, Texas
outside Amarillo
Xe reacts with F2 to form XeF2 , XeF4, XeF6
F
Xe
F
F
F
Chapter 22 Main Group Chemistry 7
8
Group 7A Halogens
Fluorine
F, Cl, Br, I
1-
Hydrogen halides, HX
acids
Oxyacids
ion
acid
Ox. No.
Hypochlorite,
ClO–
Hypochlorous,
HClO
1+
Chlorite,
ClO2–
Chlorous,
HClO2
3+
Chlorate,
ClO3–
Chloric,
HClO3
5+
Perchlorate,
ClO4–
Perchloric,
HClO4
7+
Cl2 + H2O  Cl-(aq) + OCl-(aq) + 2H+(aq)
NaOCl
household bleach
Interhalogen compounds
XX'
XX'3
XX'5
ClF
ClF3
ClF5
BrF
BrF3
BrF5
IF
IF3
IF5
ICl
ICl3
XX'7
BrCl
IBr
Chapter 22 Main Group Chemistry 8
IF7
9
Group 6A
O, S, Se, Te, Po
Oxygen, O2, O3 (ozone)
peroxide
O22-
superoxide O2-
Sulfur
Oxidation number 2- (H2S), 4+, 6+
Oxides, SO2 SO3
VO
2
5
SO2 g  O2 g  


 SO3 g
SO3 g  H2SO4 l   H 2S2 O7 l
H2 S2O7 l   H2Ol   2H 2SO4 l 
S + O2
SO2
H2SO4 + SO3
O2
catalyst
V2O5
H2S2 O7
SO3
H2O
H2O
Pyrosulfuric acid
Oxy acid
H2SO3
sulfurous acid
H2SO4
sulfuric acid desiccant, drying agent,
Chapter 22 Main Group Chemistry 9
H2SO4
2 H2 SO4
10
Thiosulfate, S2O32–
reducing agent
8SO3 2– aq   S8 s   8S 2O3 2 aq
O
S
S
O
O
O
O
S
O
O
SO42–
S2O32–
Group 5A N, P, As, Sb, Bi
Nitrogen
Oxidation numbers
NH3
(3–)
H2N–NH2
(2–)
NH2F
(1–)
N2
(0)
3– to 5+
Nitrogen oxides
N2O
nitrous oxide (laughing gas)
NO
nitric oxide
NO2
nitrogen dioxide
Chapter 22 Main Group Chemistry 10
11
NH3
O2
O2
850°C
Pt
NO2
NO
H2O
HNO3
NO byproducts
Nitric Acid: Fertilizers as NH4NO3
Plastics
Drugs nitroglycerin
Explosives, TNT
Phosphorus
white phosphorus, P4
red phosphorus, polymeric
Phosphorus oxides
P4O6
P4O10
phosphorus pentoxide
desiccant
add water
H3PO4
fertilizers, soda (check ingredients of your can of Coke)
Condensation
combine two molecules, lose water
ex: amino acids to form polypeptides
Chapter 22 Main Group Chemistry 11
12
glycine
O
H2N
CH C
OH
O
CH3
H2N
CH C
OH
CH3
O
H2N
O
CH C
N
H
CH3
CH C
+ H 2O
OH
CH3
2H3 PO 4  H4 P2O7  H2O
H4P2O7
pyrophosphoric acid
nH 3 PO 4  HPO3 n  nH 2 O
O
OH
O
P
O
HO
O
P
O
P
O
P
O
O
O
O
P
OH
O
OH
OH
ATP
adenosine triphosphate
ADP
adenosine diphosphate
AMP
adenosine monophosphate
NH2
C
N
H
O
H
O
O
O
P
P
O
H
O
H
O
P
O
H
O
O
CH2 O
CH
C
N
C
C
N
C
N
C
CH CH
H
OH OH
Adenosine
Chapter 22 Main Group Chemistry 12
H
13
PCl3
xs P + Cl2
P + xs Cl2
Arsenic
xs As + F2
PCl5
toxic
As + xs F2
AsF3
AsF5
Antimony
Bismuth - Pepto-Bismol®
Group 4A
C, Si, Ge, Sn, Pb
Carbon
graphite
layered - solid lubricant
diamond
tetrahedral geometry
hardest material, industrial drill bits, grinding material
carbonates

CaCO3 s 
CaOs  CO 2 g
carbides, silicon carbide "carborundum"
abrasive
Chapter 22 Main Group Chemistry 13
14
Silicon
Elemental semiconductor
SiO2 silica
glass (super cooled liquid)
quartz (highly crystalline)
Silicates, zeolites (Na2(Al2Si3O10)
Silicones, –(OSiRR'O)-
H3C
CH3
H3C
Si
O
CH3
H3C
Si
O
CH3
Si
O
lubricants, cosmetics, suntan lotion, car polish, building caulk
Chapter 22 Main Group Chemistry 14
15
Germanium - semiconductor
Tin
Lead
Group 3A B, Al, Ga, In, Tl
Boron
Borax, Na2B4O7 detergent
Boric Acid, BO3H3
tooth paste, roach killer
Boron Hydrides, BH3, BH4–
Organic chemistry-reducing agent
Electron deficient compounds 3-center-2-electron bonds
H
H
H
H
B
B
H
H
Isoelectronic relationships
C-C and B-N
Aluminum
Bauxite
Al2O3•nH2O
Al2O3 used as an abrasive - sandpaper
Al2O3 + K3AlF6
form lower melting mixture than pure Al2O3
Electrolysis gives aluminum metal
Rubies!
Al2O3 with small amount of Cr3+ (as Cr2O3)
Blue sapphire
Fe2+, Ti4+
Chapter 22 Main Group Chemistry 15
16
Can be 1+ or 3+
Tl
"inert pair effect" TlBr
Thallium compounds are extremely toxic
Sodium (Na) and Potassium (K)
NaOH
soda
KNO3
pot ash
Strong Reducing Agents
Sodium
Electrolysis of Molten Sodium Chloride
Potassium
Na(g) + KCl(l)  K(g) + NaCl(l)
Group 2A
Magnesium and Calcium
Found as carbonates
MgCO3,
CaCO3
Oxides are basic
CaO
CaSO4•2 H2O
Gypsum
Limestone
(3 MgO•4 SiO2 • 2 H2O) asbestos
Properties of the elements
• High melting points
• silvery
Electrolysis of molten salts
MgCl2(l)  Mg(s) + Cl2(g)
Chapter 22 Main Group Chemistry 16