Transcript Families on the Periodic Table

Families on the
Periodic Table
Alkali Metals
• Li, Na, K, Rb, Ce, Fr
• Silvery-colored metals.
Rubidium
• They are softer than most metals and can be easily cut
with a knife to expose a shiny surface which dulls on
oxidation.
• As with all metals, the alkali metals are malleable, ductile,
and are good conductors of heat and electricity.
• VeryLithium
reactiveSodium
metals that do not occur
freely in nature
Potassium
• Volatile in water (demo)
Francium
Cesium
• Sodium
occurs mainly as NaCI (salt) in sea-water and
dried-up sea beds. Potassium is more widely distributed
in minerals such as sylvite, KCI, but is also extracted from
sea-water. The alkali metals are so reactive they cannot
be displaced by another element, so are isolated by
electrolysis of their molten salts.
Alkaline Earth Metals
• Be, Mg, Ca, Sr, Ba, Ra
• Shiny, silvery-white color
• Harder and denser than sodium and potassium, and have
higher melting points.
• High in the reactivity series of metals, but not as high as the
alkali metals of Group 1.
• All found in the Earth’s crust, but not in the elemental form as
they are so reactive. Instead, they are widely distributed in
rock structures. The main minerals in which magnesium is
found are carnellite, magnesite and dolomite. Calcium is
found in chalk, limestone, gypsum and anhydrite.
Magnesium is the eighth most abundant element in the
Earth’s crust, and calcium is the fifth.
• Only magnesium is produced on a large scale. It is extracted
from sea-water by the addition of calcium hydroxide, which
precipitates out the less soluble magnesium hydroxide. This
hydroxide is then converted to the chloride, which is
electrolysed in a Downs cell to extract magnesium metal.
Transition Metals
• Apart from Copper, the transition metals are all white lustrous
metals.
• As with all metals, the transition elements are both ductile
and malleable, and conduct electricity and heat.
• Have high melting points and high densities
• Readily form alloys with themselves and with other elements
• The interesting thing about transition metals is that their
valence electrons, or the electrons they use to combine with
other elements, are present in more than one shell. This is
the reason why they often exhibit several common oxidation
states.
• Three elements (iron, cobalt, and nickel) are the only
elements known to produce a magnetic field.
Chalcogens
• O, S, Se, Te, P
• The term "chalcogens" was derived from the Greek word
chalcos, meaning "ore formers," since they all are be
found in copper ores
• Oxygen and sulfur are nonmetals, and polonium,
selenium and tellurium are metalloid semiconductors
where their electrical properties are between those of a
metal and an insulator .
• As an element oxygen is a gas while the other group
members are solids.
• Both oxygen and sulfur can be found in pure form.
• All of the elements occur as ions in metal ores.
Halogens
• F, Cl, Br, I, At
• Fluorine is a poisonous pale yellow gas, chlorine is a poisonous pale
green gas, bromine is a toxic and caustic brown volatile liquid, and iodine
is a shiny black solid which easily sublimes to form a violet vapor on
heating.
• The term "halogen" means "salt-former" and compounds containing
halogens are called "salts".
• At room temperature all the halogens exist as diatomic molecules
• The halogens exist, at room temperature, in all three states of matter:
– Solid- Iodine, Astatine
Liquid- Bromine
Gas- Fluorine, Chlorine
• The halogens are too reactive to occur free in nature.
• Fluorine is mined as fluorspar, calcium fluoride and cryolite. It is
extracted by electrolysis as no oxidant will oxidise fluorides to fluorine.
Chlorine is also found in minerals such as rock-salt, and huge quantities
of chloride ions occur in seawater, inland lakes and subterranean brine
wells. It is obtained by the electrolysis of molten sodium chloride or brine.
Bromine is also found as the bromide ion in seawater, and in larger
quantities in brine wells, from which it is extracted. Iodine is mined as
sodium iodate(V), NaIO3, which is present in Chile saltpetre. It is
obtained by reaction with sodium hydrogensulfite.
Noble
Gases
He, Ne, Kr, Ar, Xe, Ra
•
• All elements are gases and thus boil at low temperatures
• These elements were considered to be inert gases until the
1960's, because their oxidation number of 0 prevents the
noble gases from forming compounds readily.
• However, compounds of these gases are now well
documented. Helium, neon and argon form no known
compounds.
• Krypton forms KrF2, a colorless solid
• Xenon forms a range of compounds with oxygen and fluorine.
• All noble gases have the maximum number of electrons
possible in their outer shell making them stable.
• The noble gases are all found in minute quantities in the
atmosphere, and are isolated by fractional distillation of liquid
air. Helium can be obtained from natural gas wells where it
has accumulated as a result of radioactive decay.