Atomic structure

• an atom is the smallest piece of an element that can exist
• compounds are 2 or more types of atoms that are chemically joined and are difficult to seperate
• mixtures are 2 or more types of atoms that are not chemically joined and are easy to seperate
• Separation Techniques- Chromatography

  • separates solutions based on solubility
  • place a drop of the solution on the bottom of the paper and dip it into water
  • the solvent moves up the paper and the solutes run with it
• Separation Techniques- filtration

  • separates mixtures on insoluble solids and liquids like sand and water
• Separation Techniques- crystallisation

  • separates solutions into dissolves solids and liquids
  • heat the substance
  • crystals of the solute (dissolved solids will form)
  • collect the solvent by condensation
• Separation Techniques- simple distillation

  • separates liquids with 2 different boiling point
  • mixture is heated until the liquid with the lower boiling bp starts to boil
• Separation Techniques- fractional distillation

  • separates lots of liquids with different boiling points
• Thomson's plum pudding model

  • Thomson discovered electrons
  • a ball of positive charge
  • electrons dotted about
• Rutherford's nuclear model

  • alpha scattering experiment discovered nucleus and protons
• The modern model

  • Bohr discovered electron shells
  • Chadwick discovered neutrons
• protons

  • +1
  • nucleus
  • elements atomic proton number
  • mass of 1
• electrons

  • -1
  • electron shells
  • same as protons
  • mass is almost 0
• neutrons

  • 0
  • mass of 1
• radius of atom=  1x10^-10 m
• radius of nucleus=  1x10^-14 m
• element in the same group have the same number of electrons in their outer shells
• Mendeleev's periodic table

  • he left gaps for undiscovered elements
  • atomic proton number
• properties of metals

  • high melting and boiling
  • good conductors of heat and electricity
  • all solids
• properties of non-metal

  • low melting and boiling
  • often as gases
  • do not conduct
• an isotope has the same number of protons but a different number of neutrons
• the closer a shell is to the nucleus the lower it's energy level
• Noble gases

  • group 0
  • unreactive due to full outer shell
  • boiling points increase as you go down the group
  • densities increase
• Halogens

  • 7 electrons on the outer shell
  • diatomic molecules
  • less reactive as you go down due to the attraction between the nucleus and the electron getting smaller
• Alkali metals

  • group 1
  • reactivity increases as you go down as the outer electron is less attracted to the nucleus
  • reactive with water
• Alkali metals- lithium

  • least reactive
  • red flame
  • floats on the surface
  • bubbles of hydrogen released
• Alkali metals- sodium

  • more reactive than lithium
  • metal floats
  • yellow/orange flame
• Alkali metals- potassium

  • more reactive than lithium and sodium
  • floats on the surface
  • lilac flame
• Alkali metals reacting with water

  • creates a metal hydroxide
• Alkali metals reacting with chlorine

  • metal chloride is formed
• Alkali metals reacting with oxygen

  • metal oxide is produced