C1 Atomic Structure and the Periodic Table

• What are all substances made of?

  Atoms
• What is an atom?

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

  A substance that contains only one sort of atom
• Where are atoms displayed?

  In the periodic table.
• What are the atoms of each element represented by?

  Different chemical symbols
• What is a compound?

  A substance that contains atoms of two or more elements, which are chemically combined in fixed proportions
• What are compounds represented by?

  A combination of numbers and chemical symbols called a formula
• What are chemical formulae used to show?

  The different elements in a compound.

  How many atoms of each element one molecule of the compound contains.
• How can compounds be separated?

  By chemical reactions like electrolysis.
• How can you describe what happens during a chemical reaction?

  Word equations or balanced symbol equations.
• What are the reactants?

  The substances that react.

  They are found on the left hand side of the equation.
• What are the products?

  The new substances that are formed.

  They are found on the right hand side of the equation.
• What is always equal in a reaction?

  The total mass of the products and the reactants.

  This is because no atoms are lost or made.
• What are the products of a chemical reaction made from?

  Exactly the same atoms as the reactants.
• What are mixtures?

  Substances that consist of two or more elements or compounds, which are not chemically combined.
• What do components of a mixture do?

  Retain their individual properties.
• How can mixtures be separated?

  Filtration, crystallisation, distillation, fractional distillation and chromatography.

  These processes do not involve chemical reactions, so no new substances are made
• What is filtration?

  Separation of liquids from insoluble solids.

  E.g. a mixture of salt and sand can be separated by dissolving the salt in water and then filtering the mixture.
• What is crystallisation?

  The process of obtaining a soluble solid from a solution.

  E.g. salt crystals can be obtained from a solution of salty water.
• What is the process of crystallisation?

  The mixture is gently warmed.

  The water evaporates leaving crystals of pure salt.
• What is simple distillation?

  Process used to obtain a solvent from a solution.
• What is fractional distillation?

  A process used to separate mixtures in which the components have different boiling points.

  E.g. oxygen and nitrogen can be obtained from liquid air by fractional distillation because they have different boiling points.
• What is chromatography?

  A process used to separate the different soluble, often coloured components of a mixture.

  E.g. the different colours added to a fizzy drink can be separated by chromatography.
• What was believed earlier about atoms?

  They were tiny spheres that could not be divided into simpler particles.
• Who discovered electrons?

  J.J Thomson in 1898
• What is an atom overall?

  Neutral, i.e. it has no charge
• What did Thomson believe about atoms?

  They contained tiny, negative electrons surrounded by a sea of positive charge (plum pudding model)
• What was Geiger and Marsden's experiment?

  They bombarded a thin sheet of gold with alpha particles.
• What was the result of the gold foil experiment?

  Although most of the positively charged alpha particles passed straight through, a tiny number were deflected back towards the source.
• What did Rutherford conclude from these results?

  The positive charge in an atom must be concentrated in a very small area.

  This area was named the 'nucleus'.
• What was the resulting model after the discovery of the nucleus?

  The nuclear model.
• What did Bohr deduce?

  That electrons must orbit the nucleus at specific distances, otherwise they would spiral inwards.
• Who discovered neutrons?

  James Chadwick.
• What did later experiments lead to?

  The idea that the positive charge of a nucleus could be subdivided into a whole number of smaller particles, each with the same amount of positive charge. These particles are protons.
• How big are atoms?

  Very, very small and typically have an atomic radius of about 0.1nm
• What do atoms contain?

  Three types of subatomic particles:

  Electron, neutron and proton
• Proton?

  Has a relative mass of 1.

  Has a relative charge of +1.
• Neutron?

  Has a relative mass of 1.

  Has a relative charge of 0.
• Electron?

  Has a relative mass of very small.

  Has a relative charge of -1.
• Where is almost all of the mass of an atom situated?

  In the nucleus