Chemistry Y9 C2

• Atoms


  Smallest particles that make up matter
• For some time, people thought that atoms were the smallest particles and could not be broken into anything smaller
• Subatomic particles


  • Protons
  • Neutrons
  • Electrons
• Arrangement of subatomic particles in an atom

  • Electrons are spread out around the edge of the atom in layers called shells
  • Protons and neutrons exist in a dense core at the centre of the atom called the nucleus
• Mass


  One of the two important properties of subatomic particles
• Electrical charge


  One of the two important properties of subatomic particles
• Atoms of an element contain equal numbers of protons and electrons and so have no overall charge
• Electrons have a mass of almost zero, so the mass of each atom results almost entirely from the number of protons and neutrons in the nucleus
• Atomic number


  The number of protons in an atom
• Mass number


  The sum of the protons and neutrons in an atom's nucleus
• Calculating number of neutrons

  Mass number - atomic number = number of neutrons
• Electrons


  Atoms have the same number of electrons as protons to be electrically neutral
• Electron arrangement


  • Electrons exist in layers called shells
  • Each shell has a maximum number of electrons it can hold
• Electron configuration


  The arrangement of electrons in the shells of an atom

  
• The periodic table arranges all the elements by their atomic number and properties
• The periodic table has columns called groups and rows called periods
• Physical states of elements

  • Liquids
  • Solids
  • Gases
• Reactivity of metals


  • Increases going down a group
  • Decreases going across a period
• Group 0 elements are the most unreactive
• Reactivity of non-metals and semi-metals increases up a group and along a period from left to right
• Period 1 only has 2 elements because the first shell can only hold a maximum of 2 electrons
• The outer shell of helium is complete
• The second shell is completed one electron at a time going across period 2
• The third shell is completed one electron at a time going across period 3
• The outer shell electrons in a group follow the pattern: 2,8,1; 2,8,2; 2,8,3 etc.
• The outer shell electrons across a period increase one by one
• The pattern of full electron shells in a group is: 2; 2,8; 2,8,8; 2,8,8,1; 2,8,8,2
• Alkali metals


  Elements in group 1 of the periodic table
• Properties of alkali metals

  • Shiny
  • Good conductors of heat and electricity
  • Soft and can be cut by a knife
  • Low density
  • Low melting and boiling points
• Reaction of alkali metals with water

  2M(s) + 2H2O(l) → 2MOH(aq) + H2(g)
• Reactivity of alkali metals


  Increases going down group 1
• Metals can be found in the Earth's crust combined with other elements or uncombined as pure substances
• Highly reactive metals require complicated extraction which can increase the cost
• Some unreactive metals like gold, silver and copper can be found uncombined as elements
• When a metal reacts with an acid, the products are a salt and hydrogen gas
• The salt produced depends on the metal and type of acid involved
• Reactivity series of metals

  • Potassium
  • Sodium
  • Calcium
  • Magnesium
  • Aluminium
  • Zinc
  • Iron
  • Copper
  • Gold
• Extraction of metals


  • Highly reactive metals must be extracted using electrolysis
  • Less reactive metals can be extracted by reduction using carbon, coke or charcoal
• Platinum, gold, silver and copper can occur native and do not need to be extracted
• Reaction of metals with oxygen


  Metal + Oxygen → Metal oxide