Alkali
Metals: What Most Textbooks Rarely Mention
(mostly adapted from Emsley, John.
Nature’s Building Blocks.`
Lithium,
Li It has an unusually low
density: 0.53 g/cm3. Because of this, it has to be stored in
Vaseline (petroleum jelly);otherwise it will float in
oil and be exposed to oxygen, which in turn will react with the metal.
Sodium,
Na When this metal is obtained from the electrolysis of molten NaCl, other salts are added to it to lower the melting
point, thus conserving energy. The element is then used to prepare NaBH4,
needed to bleach paper, and NaN3, which is used in air bags. You
would expect sodium to form Na3N when it reacts with
nitrogen—that compound, sodium nitride, also exists, but NaN3,
sodium azide, contains the polyatomic ion N3-1.
Potassium,
K The interior of living cells
hosts a greater concentration of K+1 than Na+1. This
supposedly reflects the ratio of the two ions that existed in the sea when life
first arose. Ironically, should the extracellular level become too high, a
massive heart attack will ensue.
When potassium is added to water,
potassium hydroxide and hydrogen are produced along with a great deal of heat.
The combination of K+1 ions, flammable gas
and high temperature combine to create a violet flame.
Rubidium,
Rb This
element is so violently reactive with H2O that it even reacts with
spunk at -100oC.
Most salts do not conduct electricity
in their solid state. An exception is RbAg4I5.
Cesium,
Cs Thrusters
that generate these ions and then accelerate them through magnetic fields are
used to steer satellites. Because of their high mass, Cs+1 push the
satellite forward before being ejected out of nozzles.
Francium,
Fr Of
the first 100 elements, francium is the least stable. Even its least transient
isotope, 223Fr, loses 50% of its identity every 22 minutes. In fact,
the only reason that there are a miniscule 30 grams at any given moment in the
earth’s crust is that it is produced by the breakdown of uranium.