Symbols in the periodic table - In class I said you should be familiar
with the symbols for the first six periods of the periodic table. I am
modifying that to say you should know the symbols for the first 30
elements + Pd, Ag, Pt, Au, Hg, Cd, U, Pu, Br, I, Pb.
Gases in the periodic table - monatomic vs. diatomic
Monatomic - gas made up of single atoms
Helium - He
Neon - Ne
Argon - Ar
Krypton - Kr
Xenon - Xe
Radon - Rn
Diatomic - two atoms of the element chemically bound together.
hydrogen - H2
nitrogen - N2
chlorine Cl2 - yellow, very reactive
fluorine F2 - colorless, very reactive
bromine - liquid at room temperature, in gas phase Br2, red
iodine - solid at room temperature, in gas phase I2, purple
Groups of the periodic table - read about them in the book to get a feel for
their properties - "Descriptive chemistry" - many interesting stories
but not enough time to cover them. You do not need to memorize the
specific examples given below.
Group 1A - alkali metals - soft metals shiny, react readily with water
Na (usually as sodium cations, as we saw in class, Na metal is very reactive) has numerous industrial uses and it is extremely
important for life (Table salt: NaCl - sodium chloride). Major component
of glass, baking soda.
Potassium chloride (KCl) is a common salt substitute (our body has more
potassium (typical adult 140g) than sodium (typical adult 100g)), but at the
same time, injection of a sufficiently concentration solution of potassium
chloride can kill you by interfering with your hearts rhythm. It is used
for lethal injections in some states.
Group 2A - alkaline earth metals - solids, typical metal, harder, less reactive
Mg (density 1.74 g / mL, compare to iron 7.86 g / mL)- very light (low
density) metal used in light weight structures, essential to life.
Ca - most abundant metal in the human body - bones (calcium phosphate)
Group 3B - 2B - transition metals - typical metals, colors, solids (except
Fe - most abundant transition metal (fourth most abundant on earth).
Major component of steel. Essential to the action of our red-blood
cells that supply our body with oxygen. More than 80% of the ocean is
largely free of life and one current belief is that this is due to iron
deficiency. "Fertilizing" barren regions of the ocean with iron
results in rapid growth of plankton.
Ti - second most abundant - strong, corrosion resistant metal
Cr - protective coatings (chrome)
Ni - with Cr, major component of stainless steel (20% Cr, 10% Ni, 70% Fe)
Cd - batteries/ Common rechargeable NiCad battery uses Ni and Cd - toxic -
Interesting balance in that it is toxic (so bad for our environment) but also of
benefit because we are reusing natural resources instead of throwing away single
Coinage metals such as Pd, Ag, Pt, Au, very unreactive.
Hg, Pb - heavy metal poisoning
Group 3A -
Al- important structural material - corrosion resistant (does react with
oxygen but this reaction yields a protective coating).
Tl - poison. once used to treat ringworm of the scalp (didn't treat ringworm
just made your hair fall out to making it easier to treat). Standard
depilatory for 50 years. In the 1930s available as an over-the-counter
cream to remove unwanted hair. Lethal dose around 800mg. Doses of
500mg were given for treating ringworm.
C - "organic" chemistry - basic building block for
life - graphite and diamond are different forms of carbon.
Si - semiconductor - computer industry, sand/quartz/glass SiO2
N - air 80% nitrogen (as N2). Very abundant, but N2
is unreactive. Essential to life, but our bodies cannot convert N2
into a usable form. We get ours from plants and other things we eat, and
we provide it to plants in a usable form when we fertilize. Some plants
can convernt N2 into usable forms on their own using an enzyme called
nitrogenase. Chemists are just now beginning to understand the action of
nitrogenase after 50 years of work.
Group 6A - Chalcogens
O - as O2 20% of the air we breathe, and of course, essential to
Se - toxic and an essential element (see Ch. 4, case in point in your text)
Group 7A - Halogens
F - As fluorides (fluorine present as an "anion" in that it has
formally gained an extra electron) - formation of fluoroapatite in bones and
teeth resulting in them being strengthened, also a common rat poison.
Again, the dose makes the difference. Component of teflon, and of CFCs (chlorofluorocarbons)
Group 8A - noble gases
Ne - neon lights
Ar - (1% of air) - important for providing an "inert atmosphere" for
many industrial processes, and in welding. The inert environment inside