2. The periodic table brings order to information about the chemical elements. It helps chemists to understand why elements react as they do. What you need to know before you start this task: You should understand the meaning of element, compound, atom and molecule. You should know that each element is represented by a symbol. How elements are presented on the periodic table? There are more than 100 elements and they are arranged in the periodic table.

3. The properties of the main groups of elements (General) The elements in group 1 are known as alkali metals. They react rapidly (very fast) with water, producing an alkaline solution and hydrogen gas. The metals become more reactive as you go down the group. The elements in group 7 are known as halogens. Fluorine and chlorine are gases. Bromine is one of only two liquid elements. Iodine is solid. They exist as diatomic molecules - they have two atoms in each molecule. As you go down the group the halogens become less reactive. The elements in group 0 are known as noble gases. They are very unreactive and exist as individual atoms ( monatomic ). The transition metals are elements which are found between groups 2 and 3. Well known examples are iron, copper and gold. They are generally quite dense (heavy) and many form brightly coloured compounds. Now try to answer some questions about the periodic table. Part of the periodic table showing the element symbols is shown below.

4. Element nameElement symbolAtomic number HydrogenH1 HeliumHe2 LithiumLi3 BerylliumBe4 BoronB5 CarbonC6 NitrogenN7 OxygenO8 FluorineF9 NeonNe10 SodiumNa11 MagnesiumMg12 Aluminium (aluminium)Al13 SiliconSi14 PhosphorusP15 Sulfur (Sulphur)