atomic structure

• Isotopes are atoms with different numbers of neutrons but the same number of protons.
• Atoms are neutral because they have an equal amount of positive charge (protons) and negative charge (electrons)
• A molecule is two or more atoms chemically bonded together.
• The mass number is the total number of protons and neutrons
• who created the plum pudding model?


  J.J. Thomson
• what happens in a chemical reaction

  1. compounds are formed or broken up
  2. at least 1 new substance is created
  3. there’s a measurable change
  4. no atoms are made or destroyed
• what elements are diatomic ?

  (i bring cley for our new house)

  1. iodine
  2. bromine
  3. chlorine
  4. fluorine
  5. oxygen
  6. nitrogen
  7. hydrogen
• what is a pure substance ?

  A substance that is made up of only one type of particle or molecule.
• what happens in filtration ?

  1. line a funnel with filter paper
  2. poor mixture into funnel
  3. let liquid drip through solids will be left behind
• what happens in crystallisation ?

  1. solution is placed in an evaporating basin and heated by a bunsen burner
  2. when the volume of solution has decreased by half remove it
  3. leave it to evaporate leaving crystals behind
• what is simple distillation used for ?

  • to separate a solvent from a solution.
• what happens in simple distillation ?

  1. salty water is heated
  2. pure water evaporates (as it has a lower boiling point)
  3. water vapour cools in the condenser and drips into beaker .
• fractional distillation

  • separates lots of liquids with different boiling points
• what happens in fractional distillation ?

  1. water and ethanol is heated
  2. ethanol evaporates first, cools, condenses.
  3. water left then evaporates cools and condenses
• fractional distillation big time

  1. vapour rises through a column, which is hotter the bottom colour at the top
  2. vapour condenses when they reach part of the column that is below, the temperature of their boiling point
  3. each liquid is laid away from the column
  4. substance of lowest BP is collected at the top
• what did jj Thompson discover?

  The electron
• what experiment did Rutherford design? (to test plum pudding model)

  alpha scattering experiment
• what were the results of the alpha scattering experiment?

  1. if alpha particle went straight through = atom is mostly empty space
  2. if particle is deflected back = contained positive particles and mass concentrated at the centre
  3. particle bounced off = hit something
• what model did rutherford create ?

  • the nuclear model
  • where the mass is concentrated at the centre of the nucleus
  • nucleus is positively charged
• what did Niels Bohr discover ?

  electrons orbit the nucleus in shells
• what did james chadwick fid evidence for ?


  Neutron
• what’s the relative atomic mass ?

  The average mass of all isotopes of an element
• what is the equation for relative atomic mass?


  (isotope 1 abundance, X mass number)

  Divide by total isotope abundance
• Proton


  • Relative mass: 1
  • Relative charge: +1
• Neutron


  • Relative mass: 1
  • Relative charge: 0
• Mass number


  Protons + neutrons
• how did mendeleev order elements ?

  in increasing atomic rate
• why was mendeleev‘s periodic table accepted ?

  1. he left gaps for unknown elements
  2. he predicted properties of these undiscovered elements
  3. when elements were found, they fit in the gaps left
• why was mendeleev wrong ?

  because he didn’t know about isotopes
• the modern periodic table

  • arranged in rows called periods in increasing atomic number
  • elements with similar properties are in vertical columns called groups
• where at the metals on the periodic table ?

  left
• what are the properties of metals (chemical reactions)

  • Lose electrons, form positive ions
• physical properties of metals

  • High, melting point and boiling point
  • good conductor of electricity and heat
  • high-density
  • Shiny
  • Malleable
• properties of non-metals

  • Low boiling point and melting point
  • Call conductor of electricity and heat
  • Dull
  • Low-density
  • Brittle
• what is group 0 called ?

  Noble gases
• noble gasses

  • extremely unreactive, do you not take part in chemical reactions
  • Because they are already have a full shell
  • As you go down the column: boiling points increase, attractive forces between atoms get stronger
• what is group 1 called?

  Alkali metals
• properties of group 1

  1. Soft
  2. Play density
  3. Low melting points
• group 1

  • all have one electron in the outer shell, making them very reactive
  • Down group, one melting point and boiling point decrease
• alkali metals react with water to produce a metal hydroxide

  sodium + water -> sodium hydroxide + hydrogen