Download Chapters 18 – The Periodic Table

Chapters 18 – The Periodic Table
See Fig. 18.1
Oxygen
0.96%
Neon
0.67%
Carbon
0.27%
Others
1.14%
Helium
36.56%
Hydrogen
60.4%
Universe
Relative Abundances
Calcium
1%
Sulfur
2%
Aluminum
1%
Nickel
2%
Others
1%
Iron
35%
Magnesium
13%
Silicon
15%
Oxygen
30%
Relative Abundances
Whole Earth
Sodium
2.83%
Calcium
3.63% Iron
Potassium Others
2.59% 0.83%
Magnesium
Titanium
2.09%
0.44%
Hydrogen
0.14%
5.00%
Aluminum
8.13%
Oxygen
46.6%
Silicon
27.72%
Relative Abundances
Earth's Crust
Phosphorous
1.00%
Calcium
1.40%
Nitrogen
3.00%
Hydrogen
10.00%
Chlorine
Potassium Sulfur
Sodium 0.14%
0.34% 0.26%
Iron
0.14%
Zinc
Magnesium
0.004%
0.003%
0.50%
Other trace
elements
0.21%
Carbon
18.00%
Oxygen
65.00%
Human Body
“Representative” Elements
• The properties of the elements are determined by
their electron configurations.
• Electron configurations (and orbital properties)
determine periodic trends:
– Electron affinity
– Ionization energy
– Atomic size
– Metal vs. non-metal characteristics
– Bonding abilities
• Each group (vertical column) shares common
properties with each other and distinct differences
from other groups based on electron configurations.
Periodic Trends in Main Groups
Periodic Trends in Main Groups: Atomic Radii
Fig .
18.2:
Atomic
radii
increase
down the
columns
Periodic Trends in Main Groups:
Ionization Energy
Ionization
energy
decreases
down the
columns
(electrons
are easier to
remove)
Group 1A Elements
H,
Li, Na, K, Rb, Cs, Fr
Alkali metals
Common Features:
All but H are very active metals
ns1 electron configuration ( n = 1 to 7)
Metals readily oxidized to X+ state
2 M+ 2 H2O  2M+ + 2OH- + H2
Vigorous reaction with water
Demo:
Reactivity of Li, Na and K
with Water
What reaction is happening here?
2Li + 2H2O  2LiOH + H2
2Na + 2H2O  2NaOH + H2
2K + 2H2O  2KOH + H2
Reaction of Li Metal with
Water
Reaction Equation:
Li(s) + H2O(l) → Li+(aq) + OH−(aq) + ½ H2(g)
The reaction of lithium with water is the slowest among
the alkali metals, even though it is the most
thermodynamically favorable. Ea is controlled by the
lattice energy (highest for Li); ΔG o by the combination
of lattice, ionization, and hydration enthalpies and
entropies (lowest for Li, largely due to the favorable
hydration enthalpy of the small Li+ ion).
Periodic Trends in Main Groups: Group 1A
Survey of Main Groups: Group 1A
Hydrogen – The Simplest Element
• Most abundant element in the universe (but not on earth,
why?)
• Colorless, odorless, highly flammable gas
• Low molar mass and non-polar…low b.p. and m.p.
• Sources:
− Combustion of methane
− Byproduct of gasoline production
− Electrolysis of water
• Major uses:
− Production of ammonia (Haber process)
− Hydrogenation of vegetable oils to produce solid
shortenings
• Typical nonmetal: covalent with other NMs, salts with very
active metals
• Hydrides: binary compounds containing H
The Chemistry of Molecular Hydrogen
Hydrogenation
H
Unsaturated fat
O
O
H
O
Fatty acid
O
Fatty acid
H2 (Ni catalyst)
H H
O
H H
O
O
Fatty acid
O
Fatty acid
Saturated fat
Hydrides
Hydrides: binary compounds containing H
Ionic hydrides: hydrogen (as H-) combines with G1A or G2A metal;
contains hydride ion and metal cation; H- is strong reducing agent
H + e
2Li + H2
H
(Hrxn = - 73 kJ/mol)
2LiH
Covalent hydrides: hydrogen combines with other nonmetals…we
already know about many of these (HCl, CH4, NH3, H2O)
Metallic (interstitial) hydrides: transition metal catalysts treated with
H2 (g); H2 molecules dissociate at the metal surface and H atoms
occupy holes in the crystal structure (potential use as a portable fuel)
Reaction of Lithium Hydride with Water
Reactions of ionic hydrides with water are violent.
LiH(s) + H2O(l) → Li+(aq) + OH–(aq) + H2(g)
The H – ion in LiH (and other column-I and -II hydrides) is a strong
base, reacting with any molecule containing acidic H to form
H2(g). These reactions can also be regarded as oxidationreduction.
However, the reaction is much milder than most redox reactions,
suggesting that it is best considered as acid-base from a
practical standpoint.
Small amounts of undissolved material are probably Li2CO3(s),
formed by reaction of LiH(s) with CO2(g) and H2O(g) in the air.
Group 2A Elements
Be, Mg, Ca, Sr, Ba, Ra
Alkaline earth metals
Common Features: All are reactive metals (Be and Mg less
reactive with water at 25°C)
ns2 electron configuration (n = 2 to 7)
Readily oxidized to X2+ state
M + 2H2O  M2+ + 2OH- + H2
Form “insoluble” salts (carbonates, phosphates, sulfates, fluorides)
Some metal oxides have limited solubility in water (MgO, CaO, Al2O3)
Periodic Trends in Main Groups: Group 2A
Table 18.7
Be2+
Mg2+
Ca2+
Sr2+
Ba2+
Ra2+
Biological Properties
Be
Highly toxic
Mg
Ca
Biogenic…metabolism and muscles
Biogenic…bones and teeth
Sr
Ba
Highly toxic
Highly toxic; sulfate insolubility – used for x-ray
enhancement
Highly toxic; radioactive, t1/2 = 1,622 years
Ra
Chlorophyll – The most important Mg compound
CO2 + H2O
catalyst
(CH2O) + O2
Sugars, cellulose
Chromophore
Respiration
Group 2A Elements: Water Hardness
Ca2+(aq) + CO32¯(aq) CaCO3(s)
Precipitates as calc at elevated temperatures
Ca2+, Mg2+ Ion Removal from Water
by Ion Exchange
Mg + O2
• Magnesium is a highly flammable metal
• Once ignited, it is difficult to extinguish – it can burn
in nitrogen, carbon dioxide and water
• Magnesium powder is used in fireworks and marine
flares
• Mg2+ is the second most common cation in seawater
Periodic Table of Elements
Group 3A Elements
B
Non-metallic
Al, Ga, In, Tl
Metals
Common Features:
ns2p electron configuration (n = 2 to 6)
Cannot achieve valence electron octets in neutral molecules
B and Al form strong bonds to F and O
H
F
B
F
O
3 H2 O
F
B
O
H
O
H
Boron trifluoride
Boric acid
(+ 3 HF)
Periodic Trends in Main Groups: Group 3A
Table 18.8
Increase in metallic character going down the group.
How Can Group 3A Elements Achieve Electron Octets?
Bridging bonds
H
H
B
H
H
B
+
H
H
H
H
H
B
H
B
H
H
Hrxn = -165 kJ/mol
Covalent boron hydrides: “boranes” (e- deficient, highly reactive)
Fig. 18.7
How Can Group 3A Elements Achieve Electron Octets?
:
: F:
:
F
B
F
F
F
B
F
F
F
Reactions with
anion electron donors
Tetrafluoroborate anion
:
:
:
O
H
B
O
H
H
B
H
H
H
Reactions with
neutral electron donors
Ether-BH3 complex
How Can Group 3A Elements Achieve Electron Octets?
Cl
2
Cl
Al
Cl
Cl
Al
Al
Cl
Cl
Cl
Cl
Cl
nH2O
O
HO
Al
Aluminum hydroxide
polymers
O
O
O
Al
O
Al
OH
Aluminum
chloride dimer,
Al2Cl6
Periodic Trends in Main Groups: Group 3A
Aluminum
 Most abundant metal in Earth’s crust
 Metallic properties, but covalent bonds to NMs
 Covalency: amphoteric Al2O3, acidic Al(H2O)63+
Amphoteric Nature of Aluminum Hydroxide
Substances like Al(OH)3(H2O)3(s) that can act as either acids or
bases are called amphoteric.
Aluminum hydroxide is formed by the following neutralization
reaction:
Al(H2O)63+(aq) + 3 OH–(aq) → Al(OH)3(H2O)3(s) + 3 H2O(l)
Cl–, NH4+ spectator ions.
The subsequent neutralization reactions are as follows:
Al(OH)3(H2O)3(s) + 3 OH−(aq) → Al(OH)63−(aq) + 3 H2O(l)
Na+ spectator ion.
Al(OH)3(H2O)3(s) + 3 H3O+(aq) → Al(H2O)63+(aq) + 3 H2O(l)
Cl− spectator ion.
Thermite Reaction
Reaction Equation:
Fe2O3(s) + 2 Al(s) → 2 Fe(s) + Al2O3(s)
ΔHo = –849 kJ/mol
ΔSo = –37.48 J/mol-K
ΔGo = –838 kJ/mol
Uses:
welding, purifying an ore
(U in the Manhattan Project)
In this reaction, an unfavorable ΔS is offset by a very large
negative ΔH. The heat is sufficient to raise the temperature of
the products past the melting point of Fe (1530 °C).
Can go horribly wrong…the heat has to go somewhere and a
sand pit is the best
“Mythbusters”: thermite and ice…ice chunks flew 150 feet, or
half a football field
Group 4A Elements
C
Non-metallic
Si, Ge
Metalloid
Sn, Pb
Metals
Common Features:
ns2p2 electron configuration (n = 2 to 6)
Can achieve valence electron octets in neutral molecules
All form covalent bonds with other nonmetals
C: s and p bonds, as in CH4, O=C=O, H-CN, etc.
Si: prefers s bonds, as in SiCl4 , SiH4, or network solids (SiO2)
Ge: prefers s bonds, as in GeCl4
Sn: forms covalent s bonds, as in SnH4, but also ionic bonds,
as in SnCl2.
Pb: forms covalent s bonds, as in Pb(C2H5)4 ,(tetraethyl lead),
but also ionic bonds, as in PbSO4 (paint filler). Toxic!!
Group 4A Elements
C: graphite, diamond, fullerene
second most abundant element in human body
(more to come in Ch 21)
Si: semimetal (semiconductor for electronics)
second most abundant element in Earth’s crust
Ge: semiconductor for electronics (transistors)
Sn: tin foil, bronze, solder, pewter, protective coating for steel
Pb: anti-knocking agent in fuels (problematic for catalytic
converters), lead crystal (extra sparkly, but toxic!), car
batteries
Periodic Trends in Main Groups: Group 4A
Note: Si-Si compounds do exist, but are more reactive than
the corresponding C-C bonds. This is why we see more Si-O
bonds than Si-Si bonds.
Reactions of Main Group Elements: Group 4A
Group 5A Elements
N, P
Non-metallic
As
Metalloid
Sb, Bi
Metals
Common Features:
ns2p3 electron configuration (n = 2 to 6)
Electronegativity decreases down the group
Metallic character increases down the group
N and P: form 3- anions in salts with active metals
Bi and Sb: form mostly 3+ rather than 5+ ions
Group 5A elements can form molecules involving 3, 5,
or 6 covalent bonds to the Group 5A atom
MX3: NH3, PH3, NF3, AsCl3, AsF3
contain a lone pair of electrons (Lewis base, pyramidal
shape)
MX5: PF5, PCl5, SbCl5, AsF5
the small atomic size of nitrogen makes it difficult to
accommodate 5 covalent bonds; prediction of
VSEPR model – trigonal bipyramidal
MX6: MX5 + X-  MX6e.g. PF5 + F-  PF6AsF5 + F-  AsF6-
(phosphorous hexafluoride anion)
(arsenic hexafluoride anion)
The Chemistry of Nitrogen
• Elemental nitrogen exists as N2 molecules
N N,
2 p bonds
941 kJ/mol bond energy
• Other elements in Group 5A do not form p bonds, but exist
as aggregates with single bonds (e.g. P4, As4, etc.)
• The strong N N bond makes N2 very unreactive toward
most other substances (inert atmosphere)
• Many N-containing compounds decompose exothermically
to N2, releasing large amounts of energy
Examples:
N2O(g)  N2(g) + ½ O2(g)
∆H = -82 kJ/mol
N2H4(g)  N2(g) + 2 H2(g)
(hydrazine)
∆H = -95 kJ/mol
4 C3H5N3O9(l)  6 N2(g) + 12 CO2(g)
(Nitroglycerine)
+ 10 H2O(g) +O2(g) + Energy!
4 moles of liquid  29 moles of gas with large bond energies!
2 C7H5N3O6(s)  12CO(g) + 5H2(g) + 3N2(g) + 2C(s) + Energy!
(trinitrotoluene, TNT)
2 moles of solid  20 moles of gas + energy!
Reacts spontaneously with
strong oxidants (H2O2, NO2)
– used as self-igniting fuel in
torpedoes, rockets, space
shuttle
Some Important Nitrogen Reactions
1. Nitrogen is “fixed” industrially in the Haber process under
high temperature and heat, and with a catalyst:
N2 (g) + 3 H2 (g)
2 NH3 (g)
2. Further industrial reactions convert NH3 to NO, NO2, and
HNO3, (e.g. Ostwald process):
4 NH3(g) + 5 O2(g)
4 NO(g) + 6 H2O(g)
nitric oxide
3. NO can also be made directly from N2 at high temperatures
(like in an internal combustion engine):
N2(g) + O2(g)
2 NO(g)
A Few Important Compounds of Nitrogen
1. Ammonia, NH3. First substance formed when atmospheric N2 is
used to make N-containing compounds. Annual multimillion-ton
production for use in fertilizers, explosives, rayon, and polymers
such as nylon, urea-formaldehyde resins, and acrylics.
2. Hydrazine, N2H4. Used in rockets as a propellant, and as a
starting point for anti-tuberculin drugs.
3. Nitric oxide (NO), nitrogen dioxide (NO2), and nitric acid
(HNO3). Used in fertilizer manufacture, nylon production, metal
etching, explosives industry, and biological signaling, among other
things.
4. Amino acids, H3N+-CH(R)-COO- (R = one of 20 different organic
groups). Occur in every organism, both free and linked together
into proteins. Essential to growth and function of all cells.
Phosphorus
No double bonds
P
P
P
P
White phosphorus
- soluble in non-polar solvents
- toxic
- highly reactive to oxidation
P
P
P
P
P
P
P
P
P
Red phosphorus
- network/polymeric
- insoluble
- less reactive
3 P4(s) + 10 KClO3(s)  3 P4O10(s) + 10 KCl(s)
Heat of reaction = - 9,425 kJ/mol
The head of "strike anywhere" matches contain an oxidizing
agent such as potassium chlorate together with tetraphosphorus
trisulfide (P4S3), glass and binder. The phosphorus sulfide is easily
ignited, the potassium chlorate decomposes to give oxygen, which
in turn causes the phosphorus sulfide to burn more vigorously.
The head of safety matches are made of an oxidizing agent
such as potassium chlorate, mixed with sulfur, fillers and glass
powder. The side of the box contains red phosphorus, binder and
powdered glass. The heat generated by friction when the match is
struck causes a minute amount of red phosphorus to be converted
to white phosphorus, which ignites spontaneously in air. This sets
off the decomposition of potassium chlorate to give oxygen and
potassium chloride. The sulfur catches fire and ignites the wood.
Group 6A Elements
O, S, Se
Non-metallic
Common Features:
Te, Po
Metalloid
 ns2p4 electron configuration (n = 2 to 6)
 Metallic properties increase down the column, but no G6A
element behaves like a true metal
 Common behavior: reaction with metal to become 2- ion in ionic
compound; for most metals, most common minerals are oxides or
sulfides
 Covalent bonds with other NMs; series of covalent hydrides (H2X)
 All but O have d orbitals available, so more than an octet is common
 Te and Po can be 4+ cations, but with limited chemistry
 Se interest growing in recent years (medical research)
Some Important Simple Oxygen Compounds
1. Water, H2O. Perhaps the single most important compound on earth!
2. Oxygen, O2. 21% of the atmospheric gas composition. Necessary for
all "aerobic" life forms as a source of energy. Good oxidant
thermodynamically, poor oxidant kinetically. Most of energy we
need on earth: exothermic reaction of O2 with carbon-containing
compounds
3. Hydrogen peroxide, H2O2. Used as an oxidizing agent, disinfectant,
bleach, and in the production of peroxy compounds for
polymerization.
4. Ozone, O3. Exists naturally in upper atmosphere. Absorbs UV solar
radiation, protecting the Earth's surface. Created as emission from
combustion engines- In the lower atmosphere, it is a deleterious
oxidant. Ozonolysis is used to kill bacteria in water.
5. Superoxide, HOO. (or OO.-). Incompletely reduced form of O2. Good
oxidant, bad for biological systems- superoxide reductases
From Lecture #1 this quarter… (slide 13)
142 Review POLYATOMIC (COVALENT) IONS
Some covalent molecules are stable with a net charge.
Most common examples:
Name
(“… Ion”)
Formula
Example
Related
Compound Acid
Ammonium
Hydronium
Metal Aqua
Hydroxide
Acetate
Carbonate
Nitrate
Phosphate
Sulfate
Perchlorate
NH4+
H3O +
M(H2O)62,3+
OH 
CH3CO2
CO32
NO3
PO43
SO42
ClO4
NH4Cl
HCl(aq)
Cr(H2O)6Cl3
KOH
CH3CO2K
K2CO3
KNO3
K3PO4
K2SO4
KClO4
Name
Related
(“… Acid”) Oxide
Hydrochloric
H2O
CH3CO2H
H2CO3
HNO3
H3PO4
H2SO4
HClO4
Acetic
Carbonic
Nitric
Phosphoric
Sulfuric
Perchloric
CO2
N2O5
P4O10
SO3
Cl2O7
Periodic Table of Elements
Sulfur
Found in deposits of free element and widely distributed
in ores (sulfides, sulfates)
60% in free element, 40% from purification of fossil fuels
or when sulfur-containing fuels are burned
S2 molecules only exist in gas phase at high T; stronger s
bonds than p bonds, so typically found in aggregates
Sulfur
The S8 molecule
(ring)
Figure 18.22
Sulfur Chains, Sn (n up to 10,000)
S
Odoriferous Compounds
CH3CH2CH2CH2-S-H
Skunk
CH2=CH-CH2-N=C=S
Garlic
CH3SH
Gas odorizer
H2 S
Rotten eggs and body odors
Important Reactions of the Oxygen Family (E)
1. Halides can be formed with many Group 6A elements:
E(s) + X2 (g)
various halides
(E = S, Se, Te ; X = F, Cl)
2. The other elements in the group are oxidized by O2:
E(s) + O2 (g)
EO2 (g)
(E = S, Se, Te, Po)
SO2 is oxidized further, and the product is used in the final
step of H2SO4 manufacture.
2 SO2 (g) + O2 (g)
2 SO3 (g)
SO3 (g) + H2O(l)
H2SO4 (aq)
Important Reactions of the Oxygen Family
3. Sulfur is recovered when hydrogen sulfide is oxidized:
8 H2S(g) + 4 O2 (g)
S8 (s) + 8 H2O(g)
This reaction is used to obtain sulfur when natural deposits
are not available.
4. The thiosulfate ion is formed when an alkali sulfite reacts
with sulfur:
S8 (s) + 8 Na2SO3 (aq)
8 Na2S2O3 (aq)
Some Important Compounds of the Oxygen Family
1. Hydrogen sulfide, H2S. Vile toxic gas formed during anaerobic
decomposition of plant and animal matter, in volcanoes, and in
deep sea thermal vents. Used in the manufacture of paper.
Atmospheric traces cause silver to tarnish through formation of
black Ag2S.
2. Sulfur dioxide, SO2. Colorless, choking gas formed in
volcanoes or whenever a S-containing compound (coal, oil,
metal sulfide ores, etc.) is burned. More than 90% of SO2
produced is used to make sulfuric acid. Also used as a fumigant
and preservative of fruit, syrups, and wine. As a reducing agent,
removes excess Cl2 from industrial waste water, removes O2
from petroleum handling tanks, and prepares ClO2 for
bleaching paper. Major atmospheric pollutant in acid rain.
More Important Compounds of the Oxygen Family
3. Sulfur trioxide (SO3) and sulfuric acid (H2SO4). SO3, formed
from SO2 over V2O5 catalysts, is then converted to sulfuric acid.
Sulfuric acid is the cheapest strong acid and is so widely used in
industry that its production level is an indicator of a nation’s
economic strength. Strong dehydrating agent that removes
water from any organic source.
4. Sulfur hexafluoride, SF6. Extremely inert gas used as an
electrical insulator. Also used as an atmospheric tracer of air
movement over great distances.
O - S - Se - Te - Po
Figure 18.24: Dehydration of Sucrose by H2SO4
C12H22O11 (s) + 11 H2SO4  12 C (s) + 11 H2SO4·H2O (l)
Demo: Acid Rain
During combustion sulfur combines with oxygen to form sulfur dioxide
and sulfur trioxide:
S(s) + O2(g) → SO2(g)
Predominant reaction.
2 S(s) + 3 O2(g) → 2 SO3(g) Insignificant indoors,
(Catalyzed by sunlight.)
The sulfur dioxide and sulfur trioxide then combine with water to give
acids:
SO2(g) + 2 H2O(l) ↔ H2SO3(aq)
SO3(g) + 2 H2O(l) → H2SO4(aq)
sulfurous acid
sulfuric acid
The burning of fossil fuels in industry, power plants and in homes
accounts for most of the SO2 emitted to the atmosphere. The SO2 is
oxidized by several pathways to SO3. Both SO2 and SO3 react with rain
water to form acids. The resulting acids are hazards to aquatic life and
corrode buildings made of marble. In the northeastern U. S., some
precipitation has a pH of 4.
Periodic Table of Elements
Group 7A Elements
F, Cl, Br, I, At
Non-metallic
Common Features:
 ns2p5 electron configuration (n = 2 to 6)
 All are non-metals
 Properties vary smoothly down the group, except for unexpectedly low
E.A. of fluorine and small bond energy of F2
 Highly reactive: not found as free elements in nature, but rather as
halide ions (X-) in minerals and seawater
 Highly electronegative…form polar covalent bonds with other NMs and
ionic bonds with lower O.S. metals
 Compounds with metals in higher O.S. are polar covalent (TiCl4, SnCl4)
 Astatine: radioactive, t1/2= ~8 hours
Melting Points
and Boiling
Points of the
Halogens
Larger halogens have
greater polarizabilities
larger dispersion forces
higher temperatures for phase transitions
See Table 18.18
Important Reactions of the Halogens - I
1. The halogens (X2) oxidize many metals and non-metals. The
reaction with hydrogen, although not used commercially for
HX production (except for high-purity HCl), is characteristic of
these strong oxidizing agents.
X2 (g) + H2 (g)
2 HX(g)
2. The halogens disproportionate in water:
X2 (g) + H2O(l)
X = Cl, Br, I
HX(aq) + HXO (aq)
In aqueous base, the reaction goes to completion to form
hypohalites and, at higher temperatures, halates; for example:
3 Cl2 (g) + 6 OH-(aq)
ClO3-(aq) + 5 Cl-(aq) + 3 H2O(l)
Important Reactions of the Halogens - II
3. Molecular fluorine, F2 is produced electrolytically at moderate
temperature:
2HF (as KHF2, a solution of KF in HF)
H2 (g) + F2 (g)
A major use of F2 is in the preparation of UF6 for nuclear fuel.
4. Glass (amorphous silica) is etched with HF:
SiO2 (s) + 6 HF(g)
H2SiF6 (aq) + 2 H2O(l)
F - Cl - Br - I - At
Some Important Compounds of the Halogens
1. Fluorspar (fluorite), CaF2. Widely distributed mineral used
as a flux (chemical cleaning agent) in steel making and in
the production of HF.
2. Hydrogen fluoride, HF. Colorless, extremely toxic gas used
to make F2, organic fluorine compounds, and polymers. Also
used in aluminum manufacture and in glass etching.
3. Hydrogen chloride, HCl. Extremely water-soluble gas that
forms hydrochloric acid, which occurs naturally in stomach
juice of mammals (humans produce 1.5 L of 0.1 M HCl
daily!) and in volcanic gases (from reaction of H2O on sea
salt). Made by reaction of NaCl and H2SO4 and as a byproduct of plastics (PVC) production. Used in the “pickling”
of steel (removal of adhering oxides) and in the production
of syrups, rayon, and plastics.
More Important Compounds of the Halogens
4. Sodium hypochlorite, NaClO, and calcium hypochlorite, Ca(ClO)2
Oxidizing agents used to bleach wood pulp and textiles, and disinfect
swimming pools, foods, and sewage (also used to disinfect the Apollo
11 on return from the moon). Household bleach is 5.25% NaClO by
mass in water.
5. Ammonium perchlorate, NH4ClO4. Strong oxidizing agent.
6. Potassium iodide, KI. Most common soluble iodide. Table salt
additive to prevent thyroid disease (goiter). Used in chemical analysis
because it is easily oxidized to I2, which forms a colored end point.
7. Polychlorinated biphenyls, PCBs. Mixture of chlorinated organic
compounds used as nonflammable insulating liquids in electrical
transformers. Production discontinued due to persistence in the
environment, where it becomes concentrated in fish, birds, and
mammals, and causes reproductive disturbances and possibly cancer.
Group 8A Elements
He, Ne, Ar, Kr, Xe, Rn
Non-metallic
Common Features:
ns2p6 electron configuration (n = 2 to 6) – FULL OCTET
All are non-metals
All are very non-reactive, but some compounds can be formed (XeF4,
XeF2, KrF2, etc.)
The Periodic Table
How can we organize these?
The Periodic Table
The Periodic Table
Can we predict what is missing?
The Periodic Table
The Periodic Table
• Is a convenient way to represent the elements
• It displays the trends in
– electron configuration
– metallic character
– group commonalities
• It is not the only way to do this…
…there are alternative views
Internet search: “alternative periodic tables”
MayanPeriodic.com
The shells are shown as
concentric circles. Each
row in the tabular form
is shown as a ring.
This spiral periodic table was presented by Professor Theodore
Benfey in 1964. The elements form a two-dimensional spiral,
starting from hydrogen, and folding their way around two islands,
the transition metals, and lanthanides and actinides.
Mendeleev flower
Timothy Stowe's physicists periodic table – each grouping is
for a different principal quantum number.