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Chemical Patterns Revision Atomic Structure Atoms consist of protons, neutrons and electrons. Each element has a different number of protons. The number of protons and electrons is the same in an atom. Elements are arranged in order in the periodic table. All elements in the same group have the same number of electrons in the outer shells. All elements in the same period fill a shell with electrons. Group 1 – Alkali Metals Lithium<Sodium<Potassium React with water produce hydrogen and alkaline hydroxides. React with chlorine to produce crystalline salts. Understand that some chemicals are harmful and precautions should be taken. Formulae and Equations Know the formulae for Hydrogen, water, halogens and group 1 halides and hydroxides. Write balanced equations. Using state of matter symbols, g,s,l,aq Group 7 - Halogens Recognise symbols and molecules of group 7 halogens. Recall colours and physical states of the halogens. Recall that halogens are bleaches and kill bacteria. Fluorine>chlorine>Bromine>Iodine Safety precautions when handling halogens. Spectra Elements emit distinctive colour and spectra. This can be used to identify or discover elements. Some elements would not have been discovered but for the use of spectra. Ionic Theory Compounds of group 1 and group 7 elements are ionic. Their ions are arrange in a giant ionic lattice. When molten or dissolved in water, ionic compounds of metals with nonmetals conduct electricity. Their ions are free to move when liquid. Ions An ion is an atom that has gained or lost an electron. Work out the charge on an ion based on the chemical formula and vice versa.