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    can someone help me with my chemistry homework?
    my teacher also wants me to describe how the trend in reactivity of the halogens down the group differs from that of the alkali metals down the group. I know why group 1 reactivity increases as you go down the group but I am confused on group 7 and why it is different?
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    With group 7 elements, the outer shell has 7 electrons. This means that an electron must be gained. Electrons are attracted to the nucleus, therefore if there is a short distance between the outer shell and the nucleus, it will react more. As you go down the group, there are more electron shells which causes shielding as electrons repel. The more repulsion between electrons, the further away the outer shell will be from the nucleus. This would make it harder for the element with many shells to gain an electron so reactivity will be lower. Hope this helps
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    because group 7 have 7 electrons on its outer shell so they dont need to lose any electrons also the forces of attraction between + nuclei and electrons increase the further the distance(posative and negative attract) so as we go down group 7 the number of shells(aka energy levels) increases as theres more electrons so its harder for the posative nuclei to attract electrons from other atoms so therefore less reactive

    tbis is all u need to know for gcse
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    more shells sorry*
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    (Original post by elvin.e)
    can someone help me with my chemistry homework?
    my teacher also wants me to describe how the trend in reactivity of the halogens down the group differs from that of the alkali metals down the group. I know why group 1 reactivity increases as you go down the group but I am confused on group 7 and why it is different?
    Halogens are the opposite to group 1 and group 2 because 1&2 are metals and the halogens are non metals.

    What this means is that Halogens GAIN electrons (theyre reduced) from the metals which LOSE electrons (theyre oxidised). Thats why metals form positive ions and halogens form negative ions.

    Therefore, the halogen reactivity decreases down the group due to the fact the atomic radius increases and shielding increases down the group as the molecules get bigger as they contain more electron shells, so the attraction between the incoming electron theyre trying to GAIN and the positive nucleus in weaker, so they are unable to attract the electron as easily as higher up halogens which attract the incoming electron with a lot stronger force.

    Hope this helps.
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