atomic structure and periodic table - topic 1

• Atom


  The smallest part of an element that can exist
• Atomic particles


  • Proton
  • Neutron
  • Electron
• Proton


  • Relative mass: 1
  • Charge: +1
• Neutron


  • Relative mass: 1
  • Charge: 0
• Electron


  • Relative mass: Very small
  • Charge: -1
• Atoms have no overall charge as they always have the same number of protons and electrons, which cancel each other out, and neutrons have no charge
• Ion


  The number of protons isn't the same as electrons, so they have an overall charge
• Atomic number


  The number of protons and electrons
• Mass number


  The total number of protons and neutrons
• To get the number of neutrons, subtract the atomic number from the mass number
• Element


  A substance made up of one type of atom
• Isotope


  Atoms of the same element with the same number of protons but a different number of neutrons, so they have the same atomic number but a different mass number
• Relative atomic mass (Ar)


  The average mass of the isotopes of an element
• Compound


  A substance made up of 2 or more atoms that are chemically bonded together, with different properties that can only be separated by chemical reactions
• Ionic compounds


  • Formed from metal and non-metal, consist of ions
• Covalent compounds


  • Formed from non-metals, consist of molecules
• Formula


  The chemical representation of a compound
• Mixture


  Two or more elements or compounds that are not chemically bonded together, with properties that stay the same and can be separated by physical means
• Filtration


  1. Place a beaker with a filter funnel on the top

  2. Fold filter paper into a cone shape and put in the filter funnel

  3. Pour the mixture in the funnel and the solids will stick to the paper while the solvent drips into the beaker
• Chromatography


  1. Draw a line near the bottom of the filter paper

  2. Add a spot of ink on the line and place the paper in the water (make sure the ink isn't touching the water just the paper)

  3. Place a lid on top of the container so it doesn't evaporate

  4. The water will seep up carrying the ink with it and the different ink colours will separate out

  5. When the solvent has nearly reached the top, take the paper out and leave to dry
• Evaporation


  1. Pour the solution into an evaporating dish

  2. Heat the solution with a Bunsen Burner. The solvent will eventually evaporate and the solution will get more concentrated, eventually, crystals will start to form, keeping heating until dry crystals are left.
• Crystallisation


  1. Pour the solution into an evaporating dish and gently heat the solution

  2. Evaporate half the solution and once half has evaporated, remove the dish and leave it to cool on the side

  3. Once the crystals have formed in the solution filter them out and leave them in a warm place to dry.
• History of the Atom

  • Atoms thought to be tiny spheres
  • Plum Pudding Model: JJ Thompson: A ball of positive charge with electrons embedded in them
  • Nuclear Model: Ernest Rutherford: Positively charged nucleus
  • Alpha particle Scattering experiment
  • Bohrs Nuclear Model: Neil Bohr: Electrons orbit the nucleus in shells
  • Neutrons: James Chadwick: Provided evidence that there are neutrons in the nucleus
• Electron shell rules


  • 1st shell: 2
  • 2nd shell: 8
  • 3rd shell: 8
• Electronic configuration


  Can be shown as: 2,8,1
• The Periodic table arranges elements in order of their atomic number (number of protons)
• Elements in the same group have the same amount of electrons in their outer shell and give similar properties
• Development of the Periodic Table

  • In 1800s, elements were ordered by their atomic mass
  • 20th century - realised best ordered by their atomic number
  • John Newland: Ordered by atomic mass, realised similar properties occurred every 8th element
  • Dmitri Mendeleev: Ordered by atomic mass, left gaps for elements he hadn't discovered
• The periodic table is called the periodic table because similar properties occur at regular intervals
• Isotopes made the atomic weight theory not true
• Metals


  Form positive ions when they react
• Non-metals


  Don't form negative ions when they react
• Physical properties of metals

  • Strong, hard to break, malleable, good conductors, high boiling points
• Physical properties of non-metals

  • Dull, brittle, bad conductors, lower densities
• Group 1: Alkali Metals


  • Lithium
  • Sodium
  • Potassium
  • Rubidium
  • Caesium
  • Francium
• Alkali metals


  • Have 1 electron in the outer shell
  • Very reactive
  • Soft
  • Low density
• As you go down Group 1

  Reactivity increases, melting and boiling points decrease, relative atomic mass increases
• Reaction of alkali metals with water


  1. Float

  2. Fizz

  3. Lilac flame
• Reaction of alkali metals with chlorine

  Produce white salts, more vigorous as you descend
• Reaction of alkali metals with oxygen

  Form oxides