The elements in Group 17 have the same chemical properties because each have seven valence electronsġ5 The Reaction of Chlorine, Bromine and Iodine with Water (iii) sodium hydroxide to produce salts and water. (ii) metals such as iron to produce metal halides. Group 17 elements react with: (i) water to produce acids. Therefore, the reactivity of halogens decreases down the group.ġ4 Chemical properties of Group 17 elements As the result, the halogen lower in the group has a lower tendency to attract an electron to form negative ion. Thus the forces of attraction between the nucleus and the electrons become weaker. The atomic radius of Group 17 elements increases down the group. X2 + 2e X- ,where by X = Cl, Br, or I Cl2 + 2e Cl- Br2 + 2e Br- I2 + 2e I-ġ3 The reactivity of Group 17 elements depends on its ability to gain an electron. During a chemical reaction, the atom of a Group 17 element will gain a valence electron to form univalent negative ion to attain the stable octet in its electron arrangement. The elements in Group 17 have 7 valence electrons each. The chemical reactions of Group 17 elements involve the formation of negative ions of charge –1: Cl -, Br -, I-ġ2 X2 + 2e- 2X- ,where by X = Cl, Br, or I However, the reactivity decreases down the group. Halogen Boiling point (✬) Physical state at room temperature Electro- negativity Colour Chlorine -35 Gas 3.0 Yellowish green gas Bromine 58 Liquid 2.8 Brown liquid Iodine 183 Solid 2.5 Black solidĪll Group 17 elements are very reactive. Proton number Electron arrangement Atomic radius (nm) Melting point (✬) Chlorine 17 2.8.7 0.099 -101 Bromine 36 0.114 -7 Iodine 53 0.133 114 As the atomic radius becomes larger down the group, the forces of attraction between the nucleus and electrons become weaker and thus electronegativity decreases.ĩ Some Physical Properties of Three Halogens The electronegativity decrease down the group from chlorine to iodine. Electronegativity is a measurement of the element to attract electrons.Ĩ The electronegativity decrease down the group from chlorine to iodine All halogens have high electro-negativities. Fluorine is a colourless gas chlorine is a yellowish green gas bromine is a dark brown liquid and iodine is a black solid. The colour of the halogen becomes darker down the group. Bromine is a liquid whereas iodine and astatine are solids at room temperature.ħ The colour of the halogen becomes darker down the group The first two elements (fluorine and chlorine) are gases at room temperature. More heat is required to overcome the attractive forces and therefore the melting points and boiling points increase. This is because the molecular size increases down the group.Ħ As the size increases, the van der Waal`s forces of attraction between the molecules become stronger. The melting points and boiling points of the halogens increase down the group. The forces of attraction between the molecules are weak. This is due to the increase in relative molecular mass. The reason is that as the number of filled electron shell increase down the group, the distance between the outermost electron shell and the nucleus increase. The atomic radius increase down the group. Hence, they are insulators of heat and electricity. The halogen molecules exists as diatomic molecules: F2, Cl2, Br2, I2, and At2Īll Group 17 elements are non-metals. Halogens are very reactive elements and most of them exist naturally as halide salts. The elements in Group 17 are flourine (F), chlorine (Cl), bromine (Br), iodine (I) and astatine (At). Chemical Properties of Group 17 Elementsģ Group 17 Elements The elements in Group17 are also known as the halogens. Safety Precautions in Handling Group 17 Elements 4.
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