Chemistry Topic 4

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  • Created by: Hannah
  • Created on: 28-10-12 10:46

Alkali metals are group 1 are when reacted with water form a alkaline solution. Group 2 is an alkaline Earth metal which for alkalis and many rocks in the earth have a lot of these metals in them. Halogens are group 7 and they form salts. Group 0 are noble gases and they are unreactive. Between group 2 and group 3 are the transitional metals which form a coloured compound.

The atoms in a pure metals are in a tightly packed layer which forms a regular lattice structure. The outer electrons of the metal seperate from the ions to create a sea of electrons. These electrons are delocalized and are free to move throughout the whole structure. The metal ions are postively charged and are attracted to the sea of electron. The attraction is metallic bonding. The metal ions are held tightly in neat rows that can slide over one another.

Properties of metals:

  • High melting point
  • High boiling point
  • Ductile- can be drawned
  • Malleable- are able to be bent
  • Sonorus- have a certain sound
  • Shiny
  • High density
  • conducts electricity and heat
  • strong

Conductivity: Metals are good conducters of electricity and hear in either a solid or a liquid state. They can do this by the easy mobility of the delocalised electron. The electrons move and the heave cations (positively charged metal ions) remain fixed into place and the electrons flow causing an electric current. Conductivity increase from sodium to magnesium to aliminium because the more electrons that you have, the easier it is for the electrons to move and carry a charge.

Mallebility: It can be beaten and bent into shape wihout breaking the metallic bonds. The layers of cations slide over each other as the attraction is between the cations and the sea of electrons rather than between the cations itself.

Melting Point: It decreases as you go down the group as you have the same number of electrons per atoms, but the cations which have a +1 charge are heavier and larger, therefore they are less strongly held into place by the attraction of the fixed number of delcoalised electrons. It increases across becuase the number of delocalised electrons per atoms increase and the chnages of the cations increase ( their charge), therefore they are more strongley held into place by the increasing force of reaction so a lot of energy is needed to overcome it.

Alkali Metals.

These are in group 1, they care soft and have a low melting point compared to other metlas. The flame test colours are. Lithium- red, Sodium-bright orange, Pottasium- lilac. They have a low density which enables them to float in water. They are stored in oil as if they are exposed to the air, they will immediately start reacting with the oxygen. When lithium, sodium and pottasium are placed in water; they react vigourously to form an alkaline solution which when a unviersal indicator is placed in the solution will change to eithr blue or purple.

They all have…

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