Summary Questions

• How did Mendeleev arrange the elements in his version of the periodic table?

  By increasing atomic mass and grouping elements with similar properties
• How many electrons would an element in group 1 have in its outer shell?

  1 electron
• What is the maximum number of electrons that the first three electron shells can hold?

  2, 8, and 18 electrons respectively
• What is the proton number of aluminium and its electronic structure?

  The proton number is 13, and its electronic structure is 2, 8, 3
• What is an ion?

  An ion is a charged particle formed when an atom gains or loses electrons
• Why does magnesium form ions with a 2+ charge?

  Because it loses two electrons to achieve a stable electronic configuration
• Explain why ionic compounds conduct electricity when molten but not when solid.

  In molten state, ions are free to move, while in solid state, they are fixed in place
• Describe how a covalent bond forms.

  A covalent bond forms when two atoms share one or more pairs of electrons
• Why do simple molecular substances have low melting and boiling points?

  Because the intermolecular forces between molecules are weak
• List three typical properties of giant covalent structures.

  High melting points, hardness, and poor electrical conductivity
• Name three substances that have a giant covalent structure.

  Diamond, graphite, and silicon dioxide
• What are nanoparticles?

  Nanoparticles are particles that are between 1 and 100 nanometers in size
• Name the type of molecules that plastics are made from.

  Polymers
• List three typical properties of metals that are due to their metallic bonding.

  Good electrical conductivity, malleability, and ductility
• Which type of structure is most likely to have a low melting point?

  Simple covalent structures
• What is meant by the term 'a pure substance' in chemistry?

  A pure substance is a material made of only one type of particle
• Does adding an impurity to a substance raise or lower its boiling point?

  It lowers the boiling point
• List the equipment needed for fractional distillation in the lab.

  Fractionating column, distillation flask, condenser, and receiving flask
• What purification technique should you use to obtain a pure sample of a soluble solid from a solution?

  Evaporation or crystallization
• In chromatography, what do the terms 'mobile phase' and 'stationary phase' mean?

  The mobile phase is the solvent that moves, while the stationary phase is the material that stays fixed
• Describe the method for separating a mixture by thin-layer chromatography.

  Apply the mixture to a plate, add solvent, and observe the separation of components
• How do you calculate the Rf value of a substance from a chromatogram?

  Rf value = distance traveled by substance / distance traveled by solvent front
• What is the 'relative atomic mass' of an element?

  It is the weighted average mass of an atom of an element compared to 1/12th of the mass of carbon-12
• How do you work out the relative formula mass of a compound?

  Add together the relative atomic masses of all the atoms in the formula
• What is the empirical formula of a compound?

  The simplest whole-number ratio of atoms of each element in a compound