Groups (PT), RoR, Heat energy changes in Chemical Reaction

• Group 1

  • Alkali metals
  • Lithium, sodium, potassium, rubidium, caesium, franicum
  • Soft
  • Low density
  • Low melting point
  • More reactive as going down the group, as radius of atom is bigger so less attraction to nucleus so easier to lose
  • MP and BP decrease as going down
  • Have one electron which is easy to get rid of
  • Form ionic compounds (electrostatic forces)
  • Form white compounds + colourless in water
• Alkali metal reactions

  • React vigorously with water, forms metal hydroxide + hydrogen gas
  • React vigorously when heated with chlorine gas, forms white salt
  • When react with oxygen they form a metal oxide
• Group 7

  • Halogens
  • Diatomic molecules
  • MP and BP increases as you go down group
  • Reactivity decreases as you go down group - shell gets bigger meaning the force used to pull in an electron gets weaker
  • They form halides as they bind with alkali metals
  • Displacement reaction - more reactive halogen replaces less reactive in a halide
• Rate of reaction

  $rate\ of\ reaction=$$\frac{Quantity\ of\ reactnts\ used\ or\ producs\ formed}{time\ taken}$
• Factors affecting reaction rates

  • Concentration of reactants: more particles = more collisions
  • Surface area: More surface area = increases frequency of collisions as there is more space
  • Pressure of gases: Higher pressure = Makes particles closer together, increases frequency of collisions
  • Temperature: Higher temperature = More frequent collisions, particles have more energy and move quicker
• Catalysts

  • Used to speed up chemical reactions
• Exothermic Reaction

  • A reaction that releases energy to the surroundings
• Endothermic reaction

  • Energy is taken in from surroundings