![]() Secondly, this ability to attract electrons towards the nucleus of the atom decreases as you go down group 17 from top to bottom, fluorine is more electronegative than chlorine which is more electronegative than bromine which is more electronegative than iodine. Remember, gaining an electron is favourable for halogens because it enables them to form an anion with the same electron configuration as a stable Group 18 (Noble Gas) element. This is why we say that the properties of group 17 elements become more metallic in character as you go down the group from top to bottom, even though all the elements in group 17 are non-metals.įirstly, all the halogen atoms are very electronegative, they are all very capable of pulling an electron towards themselves. Pale yellow to greenish-yellow to reddish-brown to gray There is also a gradation in the colour of the elements going down group 17 from top to bottom: We can infer that there is a gradation in the intermolecular forces acting between the molecules such that the strongest forces of attraction act between iodine molecules and the weakest forces of attraction act between fluorine molecules. The melting point of a substance reflects the amount of energy required to weaken the forces of attraction between molecules ( intermolecular forces), the higher the melting point the stronger the forces of attraction between the molecules. Going down Group 17 from top to bottom the elements change from gaseous state to liquid to solid. We can see a trend in the states of matter. Summary of trends in the properties of Group 17 elements is shown below: Metallic character of the group 17 elements increases down the group from top to bottom.Elements become darker in colour going down group 17 from top to bottom.Melting point and boiling point increase down Group 17 from top to bottom.First ionization energy decreases down group 17 from top to bottom.Chemical reactivity of group 17 elements decreases down group 17 from top to bottom.Electronegativity decreases down group 17 from top to bottom. ![]() Atomic radius increases down Group 17 from top to bottom.All Group 17 (group VIIA or halogen) elements have 7 valence electrons (7 electrons in the valence shell or highest energy level).(ii) covalent (eg, non-metal + halogen → non-metal halide) (i) ionic (eg, metal + halogen → metal halide) Group 17 elements can combine with nearly all the elements in the periodic table.Group 17 elements exist as diatomic molecules (X 2) when not combined with other elements.(a) halogens (2) (name still in common use) ![]()
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