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.