Topic 1 - Key concepts

• Atom


  Consists of a nucleus with protons and neutrons, and electrons in shells around the nucleus
• Subatomic particles


  • Protons
  • Neutrons
  • Electrons
• Protons


  Positively charged particles in the nucleus

  +1 relative charge

  1 relative atomic mass
• Neutrons


  Neutral particles in the nucleus

  0 relative charge

  1 relative atomic mass
• Electrons


  Negatively charged particles in shells around the nucleus

  • -1 relative charge
  • 1/1836 relative atomic mass
• Atomic models


  • Dalton's billiard ball model
  • Thompson's plum pudding model
  • Rutherford's planetary model
  • The modern model (Niels Bohr)(James Chadwick)
• Isotope


  An atom of the same element with the same number of protons different number of neutrons
• Relative atomic mass


  Average of all the isotopes of an element
• Periodic table


  Organizes elements by atomic number and properties
• Group number


  Number of electrons in the outer shell
• Period number


  Number of shells the atom has
• Ionic bond


  Bond between a metal and a non-metal formed by the loss or gain of electrons
• Ion


  Charged particle formed by the loss or gain of electrons
• Cation


  Positive ion formed by the loss of electrons
• Anion


  Negative ion formed by the gain of electrons
• Ionic compounds


  • Form a giant ionic lattice
  • Have high melting and boiling points
  • Can conduct electricity when molten or dissolved as ions cannot move in a solid but can in a liquid
  • Strong electrostatic forces between ions
• Covalent bond


  Bond between non-metals formed by the sharing of electron pairs
• Polyatomic ion


  Ions where the charge is on the whole compound
• Spectator ions


  Ions that don't change before and after a reaction
• Covalent bond


  Bond between non-metals where electrons are shared
• Covalent bonds- simple molecule

  • Low melting point
  • Weak intermolecular forces between covalent molecules
  • Does not conduct electricity
  • No free electrons so it cannot carry a charge
• Allotropes of carbon


  • Diamond
  • Graphite
• Diamond


  • Very hard and strong due to triangular and pyramid shape
  • Cannot conduct electricity as each carbon is bonded to 4 others with no free electrons
• Graphite


  • Layers can slide over each other making it a good lubricant
  • Can conduct electricity as each carbon is only bonded to 3 others leaving a spare electron
• Metallic bond


  Metal atoms give up their electrons which delocalize, forming positive metal ions with strong electrostatic forces
• Mole


  A special number, 6.02 x 10^23, that links mass to the number of atoms in a sample
• Relative formula mass


  Total mass of a compound, found by adding the masses of the atoms
• Empirical formula


  The simplest whole number ratio of the atoms in a compound
• Covalent compound - giant covalent lattice


  • High melting point
  • Strong covalent bonds between atoms
  • Does not conduct electricity
  • No free electrons so it cannot carry a charge