EDEXCEL Chemistry Paper 2

• Who published the three-part atomic theory in 1803?

  John Dalton
• What are the main points of Dalton's atomic theory?

  • All substances are made of atoms.
  • Atoms cannot be created, divided, or destroyed.
  • Atoms of the same element are identical.
  • Atoms of different elements are different.
  • Atoms combine to form new substances.
• How has the Dalton model of an atom changed over time?

  Due to the discovery of subatomic particles
• What was proven incorrect about Dalton's atomic theory?

  Atoms can be divided into smaller parts
• What experiment did J.J. Thomson conduct in 1897?

  Used a cathode-ray tube
• What did Thomson's experiment reveal about atoms?

  Atoms can be divided into smaller parts
• What charge did Thomson determine the particles had?

  Negative charge
• What is the "plum-pudding" model proposed by Thomson?

  Electrons scattered in positive material
• What experiment did Ernest Rutherford conduct in 1909?

  Shot particles into gold foil
• What did Rutherford's experiment show about atomic structure?

  Most of the atom is empty space
• What did Rutherford conclude about the atom's mass?

  Most mass is in the nucleus
• How do electrons move in Rutherford's atomic model?

  In random paths around the nucleus
• What is the structure of an atom?

  • Nucleus containing protons and neutrons
  • Electrons surrounding the nucleus in shells
• What particles are found in the nucleus of an atom?

  Protons and neutrons
• Where are electrons located in an atom?

  In shells surrounding the nucleus
• What is essential to know in chemistry?

  About chemical equations
• How can chemical changes be represented?

  Using word equations and symbol equations
• What do symbol equations show?

  Atoms on both sides of the equation
• Why must symbol equations be balanced?

  To ensure the same number of atoms on both sides
• How do you balance a chemical equation?

  By putting numbers in front of the formulae
• What is the balanced equation for sulfuric acid and sodium hydroxide?

  H₂SO₄ + 2NaOH → Na₂SO₄ + 2H₂O
• What happens when you change the formula in a chemical equation?

  You disrupt the balance of atoms
• What is the first step in balancing an equation?

  Find an unbalanced element
• What do state symbols indicate in a chemical equation?

  The physical state of substances
• What does (s) represent in a chemical equation?

  Solid state
• What does (l) represent in a chemical equation?

  Liquid state
• What does (g) represent in a chemical equation?

  Gas state
• What does (aq) represent in a chemical equation?

  Aqueous state
• What is the balanced symbol equation for hydrochloric acid and calcium carbonate?

  2HCl(aq) + CaCO₃(s) → CaCl₂(aq) + H₂O(l) + CO₂(g)
• What are the formulas for common molecules you should learn?

  H₂O, NH₃, CO₂, H₂, Cl₂, O₂
• What is the formula for Ammonium ion?


  NH₄⁺
• What is the formula for Hydroxide ion?

  OH⁻
• What is the formula for Nitrate ion?

  NO₃⁻
• What is the formula for Carbonate ion?


  CO₃²⁻
• What is the formula for Sulfate ion?

  SO₄²⁻
• What do ionic equations show?

  Only the reacting particles in solution
• How do you write an ionic equation?

  Remove aqueous ions present on both sides
• What is the ionic equation for CaCl₂ and NaOH?

  Ca²⁺ + 2OH⁻ → Ca(OH)₂(s)
• What is a hazard in chemistry?

  Anything that can cause harm
• What is the risk associated with a hazard?

  The chance of harm from exposure