![]() Halogens have an incredibly high reactivity rate, therefore the only halogens found in the environment are as compounds or as ions. This concludes that when there is a reaction with another element, it would take one electron in order to obtain full electronic configuration. The location of the Halogens reflects the amount of electrons in the outer shell i.e it’s in group 7 therefore it has 7 electrons in the outer shell. Iodine crystals are shiny purple (but usually turn into a dark purple vapour when they are warmed). Fluorine is a very pale yellow, chlorine is a yellow-green, and bromine is a red-brown. There’s another trend shown in this group as the halogens become darker as you go down the group. This is another pattern in state from gas to liquid down the group. ![]() If we look at the graph, we can see that at this temperature fluorine and chlorine are gases, bromide is a liquid, and iodine and astatine are solids. The dotted line represents room temperature, usually taken at 25☌. Melting and Boiling points of the Group 7 Elements They react with metals to form metal halides, and with hydrogen to form acidic hydrogen halides. As you can see from the graph below, the boiling and melting points rise: Group 7 - the halogens The group 7 elements are all reactive non-metals. There is a definite pattern when looking at the melting and boiling points as you go down the group. This means that chlorine reacts less vigorously with sodium than. Some of the uses for Astatine (211): Sometimes used as a radioactive tracer and in cancer treatment The chemical reactivity (how vigorously they react) of the halogens decreases down group 7.Some of the uses for Iodine: Essential for the body’s thyroid gland (without iodine, thyroid hormones cannot be produced).Some of the uses for Chlorine: Disinfectants for sterilisation.Some of the uses for Fluoride: Toothpaste, vitamin supplements and even water.Some of them have uses for things in the world, below is a list. The six elements in group one are: Fluoride, Chlorine, Iodine and Astatine. It is called the “shielding effect.” This reduces the ionization energy and the electron affinity of the ions, therefore reducing the reactivity These levels of electrons act as a “shield” between the valence electrons and the pull of the positive nucleus. It decreases as you go down the group.Īs you go down the group the atomic radius (and ionic radius) increases due to additional levels of electrons. Another trend going down group 7 is their reactivity. All halogens have 7 electrons in their outer shells, giving them an oxidation number of -1.Īs you go down the group the trend in the atomic radius is that it increases the further down you go. ĭiscusses the acidity of the hydrogen halides (like hydrogen chloride), and explains why HF is a weak acid.ĭescribes and explains the trend in reducing ability of the halide ions based on their reactions with concentrated sulphuric acid.ĭescribes and explains the tests for halide ions using silver nitrate solution followed by ammonia solution.ĭescribes the manufacture of chlorine by the electrolysis of sodium chloride solution using a diaphragm cell and a membrane cell.The halogens are five non-metallic elements found in group 17 of the periodic table. ![]() ![]() The reactions of halogens with hydrogen, phosphorus, sodium, iron, iron(II) ions, and sodium hydroxide solution. It also looks at the bond strengths of halogen-halogen bonds and of hydrogen-halogen bonds.ĭescribes and explains the trend in oxidising ability of the Group 7 elements based on the reactions between one halogen and the ions of another one - for example, between Cl 2 and I - ions from salts like KI. The higher up we go in group 7 (halogens) of the periodic table, the more reactive the element. My reasons for not using the IUPAC system are discussed on this page in the Questions and Comments section.ĭiscusses trends in atomic radius, electronegativity, electron affinity and melting and boiling points of the Group 7 elements. Note: If you use the current IUPAC (international Union of Pure and Applied Chemistry) system for group numbering, you will probably know what I call Group 7 as Group 17. Periodic Table Group 7 menu Understanding Chemistry ![]()
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