TOPIC 1 ATOMIC STRUCTURE

• What is an atom?


  The smallest part of an element that can exist
• What is an element?


  A substance that is only made up of one type of atom
• What is a compound?


  Two or more elements chemically combined in fixed proportions
• What is the symbol formula for carbon dioxide?

  CO₂
• What is NH₃?


  Ammonia
• What is the symbol formula for water?


  H₂0
• What is NaCl?


  Sodium chloride
• What is the symbol formula for carbon monoxide?

  CO
• What is HCl?


  Hydrochloric acid
• What is the symbol formula for calcium chloride?

  CaCl₂
• What is Na₂CO₃?


  Sodium carbonate
• What is the symbol formula for sulfuric acid?


  H₂SO₄
• What is a mixture?


  A combination of two or more elements or compounds that are not chemically combined and the chemical properties of each substance are unchanged.
• What do you use filtration for?

  Separating an insoluble solid from a liquid
• How do you separate a substance using filtration?

  You should pour the mixture into a funnel lined with filter paper over a conical flask and allow the filtrate to drip into the flask, leaving the residue behind.
• What is filtrate?


  The liquid left after filtration
• What is residue?


  The insoluble solid left behind after filtration
• What do you use crystallisation to separate?

  Crystallisation is used to separate a soluble solid from a liquid
• How do you separate a mixture using crystallisation?

  You should place an evaporating basin on a heat proof mat on a tripod over a bunsen burner. Then place your mixture in the evaporating basin and heat until the liquid evaporates, leaving the solid crystals behind.
• What do you use simple distillation to separate?


  Simple distillation separates the solvent from a liquid
• How do you carry out simple distillation?

  1) Pour your sample into the distillation flask

  2) Set up the apparatus by connecting the bottom end of the condenser to a cold tap using rubber tubing. Then run cold water through the condenser to keep it cool

  3) Gradually heat the distillation flask. The liquid will eventually evaporate.

  4) The water vapour then passes into the condenser where it cools and condenses. It then flows into the beaker where it is collected.

  5) Eventually you'll end up with just the salt (or other substance) left in the distillation flask
• What do you use fractional distillation to separate?

  It is used to separate two or more liquids with different boiling points.
• How do you carry out fractional distillation?

  1) Pour your mixture of liquids into a flask. Then attach a fractionating column and condenser above the flask.

  2) Gradually heat the flask. The different liquids will all have different boiling points so they will evaporate at different temperatures.

  3) The liquid with the lowest boiling point evaporates first. and when the temperature on the thermometer reaches the boiling point of this liquid, it will reach the top of the fractionating column.

  4) Liquids with higher boiling points might also start to evaporate but the column is cooler towards the top, so they will only get part of the way up before condensing and running back down towards the flask.

  5) When the first liquid has been collected, raise the temperature until the next one reaches the top and is ready to be evaporated.
• Why might you not use a bunsen burner during fractional distillation?

  Because some liquids such as ethanol are highly flammable and would be very dangerous to heat over a flame.
• How can you use fractional distillation to check whether a liquid is pure?

  The liquid will evaporate when it reaches its boiling point.
• What do you use chromatography to separate?

  It can be used to separate two or more dissolved solids from a solution
• How do you carry out chromotography?

  1) A spot of the mixture is placed near the bottom of a piece of chromatography paper along a pencil line.

  2) The paper is then placed upright in a suitable solvent, such as water.

  3) As the solvent soaks up the paper, it carries the mixtures with it.

  4) Different components of the mixture will move at different rates. This eventually separates the mixture out.
• What did the Greeks believe that atoms were?

  Solid, indivisible spheres
• When did J.J. Thomson discover the electron?

  1897
• What is the "plum pudding" model of the atom?

  A ball of positive charge with negative electrons studded into it
• What were the conclusions of the alpha particle scattering experiment?

  1) Most of the particles passed straight through the gold sheet - this means that most of the atom is empty space.

  
  

  2) Some particles were deflected slightly - this proves that negative electrons are scattered throughout the atom

  
  

  3) Some particles were reflected back in the opposite direction - this proves the existence of a ball of positive mass in the centre of the atom (the nucleus)
• What did Chadwick discover and when?

  The Neutron in 1932
• What is the current model of the atom called?

  The nuclear model
• When did the alpha particle scattering experiments take place?


  1911
• Who discovered the proton?

  Ernest Rutherford
• What did Bohr discover and when?

  That electrons orbit the nucleus at set distances in energy levels (shells) - 1922
• What is the size of the atomic radius?

  0.1 nm OR 1x10 m
• How big is an atom's nucleus?

  1/10,000 the size of an atom OR 1x10 m
• What is the relative charge of a proton?

  +1
• What is the relative mass of a proton?

  1