Group 1 Metals are the most reactive metals on the periodic
table and do not exist free in nature. They must be stored under oil or they will quickly oxidize . They have
very low ionization energy and give up their outer s1 electron very
easily. They are very soft metals that can be cut with a knife. They react
violently with water. The lower the ionization energy the more reactive these
metals. So the lithium is the least reactive and Cesium is the most reactive.
Like other alkali metals, lithium has a
single valence electron which it will readily lose to
form a cation, indicated by the element's low
electronegativity. As a result, lithium is easily
deformed, highly reactive, and has lower melting and
boiling points than most metals. These and many other
properties attributable to alkali metals' weakly-held
valence electron are most distinguished in lithium, as
it possesses the smallest atomic radius and thus the
highest electronegativity of the alkali group.
Lithium is soft enough to be cut with a knife, though
this is more difficult than cutting sodium. The fresh
metal has a silvery-white color which only remains
untarnished in dry air. Lithium has about half the
density of water, giving solid sticks of lithium metal
the odd heft of a light-to-medium wood like pine. The
metal floats highly in hydrocarbons; in the laboratory,
jars of lithium are typically composed of black-coated
sticks held down in hydrocarbon mechanically by the
jar's lid and other sticks.
Lithium salts were used during the 19th century to
treat gout. Lithium salts such as lithium carbonate (Li2CO3),
lithium citrate, and lithium orotate are mood
stabilizers. They are used in the treatment of bipolar
disorder, since unlike most other mood altering drugs,
they counteract both mania and depression. Lithium can
also be used to augment other antidepressant drugs. It
is also sometimes prescribed as a preventive treatment
for migraine disease and cluster headaches.
Lithium Metal foil
from an Energizer Lithium Battery
Compared with other alkali metals, sodium
is generally less reactive than potassium and more
reactive than lithium,in accordance with "periodic
law": for example, their reaction in water,
chlorine gas, etc
Owing to its high reactivity, sodium is found in
nature only as a compound and never as the free element.
Sodium reacts exothermically with water: small pea-sized
pieces will bounce across the surface of the water until
they are consumed by it, whereas large pieces will
explode. While sodium reacts with water at room
temperature, the sodium piece melts with the heat of the
reaction to form a sphere, if the reacting sodium piece
is large enough. The reaction with water produces very
caustic sodium hydroxide (lye) and highly flammable
When sodium or its compounds are introduced into a
flame it will contribute a bright yellow color.
At room temperature, pure sodium is so soft that it
can be easily cut with a butter knife. In air, the
bright silvery luster of freshly exposed sodium will
Potassium is the second least dense metal;
only lithium is less dense. It is a soft, low-melting
solid that can easily be cut with a knife. Freshly cut
potassium is silvery in appearance, but in air it begins
to tarnish toward grey immediately.
Potassium and its compounds emit a violet color in a
Potassium must be protected from air for storage to
prevent disintegration of the metal from oxide and
hydroxide corrosion. Often samples are maintained under
a reducing medium such as kerosene.
Like the other alkali metals, potassium reacts
violently with water producing hydrogen. The reaction is
notably more violent than that of lithium or sodium with
water, and is sufficiently exothermic that the evolved
hydrogen gas ignites.
Rubidium reacts violently with water and
can cause fires. To ensure both health and safety and
purity, this element must be kept under a dry mineral
oil, in a vacuum or in an inert atmosphere.
Along with gallium, francium, and mercury,
cesium is among the only metals that are liquid at or
near room temperature. Cesium reacts explosively in
cold water and also reacts with ice at temperatures
above -116 °C (-177 °F, 157 K).
Cesium, being one of the heavier alkali metals, is
also one of the most reactive and is highly explosive
when it comes in contact with water, as the hydrogen gas
produced by the reaction is heated by the thermal energy
released at the same time, causing ignition, and a
violent explosion (the same as all alkali metals) - but
cesium is so reactive, this explosive reaction can even
be triggered by cold water or ice.
Francium was discovered
by Marguerite Perey in France (from which the element
takes its name) in 1939. It was the last element
discovered in nature, rather than synthesized. Outside
the laboratory, francium is extremely rare, with trace
amounts found in uranium and thorium ores, where the
isotope francium-223 continually forms and decays. As
little as 30 g (one ounce) exists at any given time
throughout the Earth's crust; the other isotopes are
entirely synthetic. This make it the second rarest
element after astatine. The largest amount ever
collected of any isotope was a cluster of 10,000 atoms
(of francium-210) created as an ultra-cold gas at Stony
Brook in 1997.