This file contains my notes on trends taken in Unit 1 chemistry, they apply to both the BTECS applied science and forensics, as the unit is the same. Please leave a review! :3
Trends
Alkali metals
● Group 1
● Low densities
● React with water to form metal hydroxide
○ E.g Lithium + water = Lithium hydroxide
● React with non-metals to form ionic compounds
● Reactivity increases down the group
● First three (Li, Na and K) less dense than water
○ This causes them to float
● 2Na + 2H2O -> 2NaOH + H2
○ Sodium + water creating hydrogen gas and sodium hydroxide
○ Hydrogen gas can be tested for via squeaky pop test
Group 2, alkali metals
● Low density
● High melting and boiling point
● Forms metallic bonds (they are metals)
● Oxidation state +2
● Form colourless compounds
● Form ionic compounds
{ ● Tarnish in the air
● Reacts with oxygen to form metal oxide
○ When exposed to flame, it burns rapidly to produce white ionic oxide
○ Redox reaction
● Reacts with water to produce hydroxide gas
○ Mg reacts slowly in cold water but steadily with steam
○ Vigour of reaction increases down the group
● Very reactive, but less than group 1
○ Outer shell electrons are far from the nucleus
○ Ionisation energy decreases down the group
■ So reactivity increases
● Alkalinity increases down the group
● Solubility increases down the group
Group 7, halogens
● Diatomic (Never found naturally a single atom)
● Reacts with metals to form an ionic compound
○ Halogen becomes -1
● Reacts with non-metals to form a molecular compound
● Relative molecular mass increases down the group
● Melting and boiling point increase down the group
● Reactivity increases down the group
○ Outer shell is further from the nucleus making gaining electrons difficult
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