2 Chapter 6 â¢ organising elements Organising elements

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6.2 How do we organise elements? In a manner similar to that of biological classification, whereby organisms are grouped according to their similarities and differences, many other objects can be groups based on their similarities and differences. When you walk into a supermarket, the items on sale are not randomly distributed among the shelves, but are grouped according to foods versus cleaning products, as well as fresh versus packaged or frozen. Within these groupings there are further groupings, all identified by signs to assist you. The periodic table is just another example of grouping that helps you find your way efficiently around the elements. Getting elements organised Table 6.3 below lists some observable properties of a selection of common elements. This is the level of information early chemists would have had to work with in their attempts to find a unified approach to organising the elements. 1 Use the information provided in Table 6.3 to organise the elements into your own version of the periodic table. Present your periodic table to the class, complete with explanations for the arrangements and groupings you chose. 2 As a class, discuss the similarities and differences between the various periodic tables created. Critically analyse the impact of the level of information available on the table you were able to create and evaluate the restrictions this would have placed on early chemists. Table 6.3 Properties of some common elements Element Symbol State Colour Features and use Aluminium Al Solid Shiny, silver Used to make foil wrap and silver paper Carbon C Solid Black, dull Found impure in charcoal and soot Magnesium Mg Solid Shiny, silver Burns with a bright white flame Sulfur S Solid Yellow, dull Found near volcanoes, part of sulfuric acid Iron Fe Solid Silvery grey Magnetic, commonly used metal Phosphorus P Solid Dark red, dull Used on match heads, flammable Lead Pb Solid Silvery grey Used to make fishing sinkers Nickel Ni Solid Shiny, silver Main metal in ‘silver’ coins Copper Cu Solid Shiny, brown Used in electrical wires and water pipes Gold Au Solid Shiny, yellow Used in electronics, used as money Tin Sn Solid Shiny, silver Used in tin cans because it will not taint food Zinc Zn Solid Shiny, silver Metal used to galvanise iron Silver Ag Solid Shiny, silver Used in jewellery Oxygen O Gas Colourless Needed for breathing, tested with glowing splint Hydrogen H Gas Colourless Explosive, lighter than air, tested by pop test Chlorine Cl Gas Yellow–green Poison, used in bleaches and disinfectants Mercury Hg Liquid Shiny, silver Used in thermometers and some switches Calcium Ca Solid Shiny, grey Reacts quickly with water and air Iodine I Solid Shiny crystals Stains your fingers brown, sublimes easily Sodium Na Solid Shiny, grey Soft, very reactive in air and water, burns skin Potassium K Solid Shiny, white Similar to sodium Bromine Br Liquid Dark red Fuming liquid, burns skin very badly UNCORRECTED PAGE PROOFS Unit 6.2 • How are the elements organised? 11 CAS_SB10_TXT_06_1pp.indd 11 11/11/11 4:58 PM
12 Grouping elements The two main types of elements are metals and nonmetals, with metals comprising nearly three-quarters of all elements. In addition, there are some elements with properties that are between those of metals and nonmetals. These elements are termed metalloids. Metals Metals have many properties in common. Pure metals are: • lustrous (shiny) • able to conduct heat and electricity • malleable (able to be beaten into a new shape) • ductile (able to be drawn into a wire) Metals are divided into different groups according to their position in the periodic table. Group 1 metals The alkali metals, such as sodium and potassium, are found in group 1—the far left column. Their position tells us that the uncharged atoms of all the alkali metals have just one electron in the valence shell. The alkali metals have quite a low melting point and are soft and highly reactive. If you were to see them in their pure state, they often resemble plasticine that, when cut, is very briefly shiny silver before reacting with the air to become white again. Alkali metals react very strongly—some violently—with water, producing hydrogen gas and an alkaline solution. (An alkali is a soluble base.) The further down the group you go, the more violent this reaction. Chapter 6 • organising elements Fig 6.10 Xxxx. 1 2 3 4 5 6 7 Fig 6.11 Xxxx. Group 2 metals The alkaline earth metals, such as magnesium and calcium, are found in group 2. Their position tells us that the uncharged atoms of all the alkaline earth metals have two electrons in the valence shell. The alkaline earth metals have quite a low melting point and are relatively soft and very reactive, although in general they are not quite as reactive as group 1 alkali metals. Like the alkali metals, alkaline earth metals also react with water, some strongly, producing hydrogen gas and an alkaline solution. Again, the further down the group you go, the more reactive the metal. Fig 6.12 Potassium reacting with water produces a spectacular reaction. Metals Metalloids Non-metals B Si Ge As Sb Te Po Fig 6.13 Magnesium, an alkaline earth metal, (a) before burning and (b) burning. a
Page 1 and 2: 2 6 Chapter 6 • organising eleme
Page 3 and 4: 6.1 4 Why do we organise elements?
Page 5 and 6: 6 Some properties of Dobereiner’s
Page 7 and 8: 8 1894 William Ramsay, a Scottish c
Page 9: 10 Properties and structure 6.1 F
Page 13 and 14: 14 • Many of the transition metal
Page 15 and 16: 16 What do you know about non-metal
Page 17 and 18: 6.3 18 How are properties linked to
Page 19 and 20: 20 Emission spectrum and electron s
Page 21 and 22: 22 EXPERIMENT 6.2 Conductivity of i
Page 23 and 24: SKILLS LAB 24 Ionic compounds Ionic
Page 25 and 26: 26 Table 6.6 gives the electrical c
Page 27 and 28: 28 Properties and structure 6.3 Ho
Page 29 and 30: 30 >>ZOOMING OUT
Page 31 and 32: 6 Properties and structure Element
Page 33 and 34: 34 Given the fact that so many coun

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2 Chapter 6 â¢ organising elements Organising elements