topic 1- atomic structure

• What is an atom?

  Smallest part of an element that can exist
• What is an element?

  Substance of only one type of atom
• Into what two groups can elements be classified?

  Metals and non-metals
• What are new substances formed from chemical reactions called?

  Compounds
• What is a compound?

  Two or more elements combined chemically
• Do compounds have the same properties as their constituent elements?

  No, they have different properties
• What is a mixture and does it have the same chemical properties as its constituents?

  Consists of elements or compounds not chemically combined; yes, it has the same properties
• What are the five methods to separate mixtures?

  Filtration, crystallisation, distillation, chromatography
• Do the methods of separating mixtures involve chemical reactions?

  No, they do not involve chemical reactions
• What is simple distillation used for?

  To separate liquid from a solution
• How does simple distillation work?

  Liquid boils off and condenses in the condenser
• What does the thermometer read during simple distillation?

  Boiling point of the pure liquid
• How does evaporation work in separation?

  Heats solution until solvent evaporates
• What is crystallisation?

  Removing some solvent to form a saturated solution
• What happens when a saturated solution is cooled?

  Solid starts to crystallise
• How are crystals separated from the solvent?

  Via filtration
• What is fractional distillation used for?

  To separate a mixture of liquids
• How does fractional distillation work?

  Separates liquids with different boiling points
• What is the role of the fractionating column in fractional distillation?

  Helps to separate compounds by boiling points
• How does the temperature vary in the fractionating column?

  Hot at the bottom and cold at the top
• What is filtration used for?

  To separate insoluble solid from liquid
• What is the residue in filtration?

  Insoluble solid caught in filter paper
• What is the filtrate in filtration?

  Substance that comes through the filter paper
• What apparatus is used in filtration?

  Filter paper and funnel
• What is chromatography used for?

  To separate substances dissolved in a solvent
• How does paper chromatography work?

  Paper with mixture in solvent rises, separating components
• What is a separating funnel?

  Apparatus for separating immiscible liquids
• How do immiscible liquids behave in a separatory funnel?

  Form two distinct layers based on density
• What is the plum-pudding model of the atom?

  Atom is a ball of positive charge with electrons embedded
• What does the nuclear model suggest about electrons?

  Electrons orbit the nucleus at specific distances
• How did the nuclear model come about?

  From alpha scattering experiments
• What are the smaller positive particles in the nucleus called?

  Protons
• What did James Chadwick's work provide evidence for?

  The existence of neutrons in the nucleus
• Describe the structure of an atom.

  Small central nucleus with protons and neutrons, electrons orbiting
• What are the relative masses of protons, neutrons, and electrons?

  1, 1, very small
• What are the relative charges of protons, neutrons, and electrons?

  1, 0, -1
• Why are atoms electrically neutral?

  They have the same number of electrons and protons
• What is the radius of an atom?

  0.1 nm
• What is the radius of a nucleus compared to that of an atom?

  1 x $10^{-14} \text{ m}$ and 1/10000
• What is the atomic number?

  Number of protons in the nucleus