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C2: Periodic Table (The Alkali Metals (All the alkali metals are reactive.…
C2: Periodic Table
The Alkali Metals
All the alkali metals are reactive. They must be stored in oil to stop them from reacting with the oxygen in the air
The reactivity increases as you go down because the pull from the positive proton decreases making it easier to lose an electron (the electrostatic attraction is weaker)
Compared to other metals they have a very low density so they can float on water. They are also soft enough to be cut with a knife and have a silvery, shiny surface when first cut
They have one electron on their outside shell which makes them reactive because they only need to lose one electron to become stable
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When you add them to water they fizz and produce hydrogen gas. This reaction produces an alkali metal hydroxide Potassium reacts so vigorously that the hydrogen produced ignites.
The Halogens
They are toxic non-metals with low melting and boiling points that increase the further down the group
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They have seven electrons on the outside shell which makes it harder to gain electrons because the positive pull from the positive nucleus is weaker making it harder to attract an electron
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The Transition Elements
They are hard and strong, good conductors of electricity and thermal energy. They have high densities and high melting points (except mercury)
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Explaining Trends
Larger atoms lose electrons easier going down a group
Larger atoms gain electron less easy going down a group
This is because the inner shells 'shield' the outer electrons from the positive charge of the nucleus.
The electrostatic attraction depends on: the distance between the outer electrons and the nucleus, the number of shells, the size of the positive charge