chemistry paper 1

• Everything is made of atoms
• Most of the atom is made of empty space
• Subatomic particles


  • Proton
  • Neutron
  • Electron
• Proton


  Positive charge, located in the nucleus
• Neutron


  No charge, located in the nucleus
• Electron


  Negative charge, located in shells around the nucleus
• Atoms are neutral (no overall charge) because the number of positive protons equals the number of negative electrons
• You cannot change the number of protons that an atom has, but you can change the number of electrons it has through a chemical reaction
• Ion


  A charged atom that has gained or lost electrons, so the number of protons and electrons are no longer the same
• Ionisation


  The process where an atom loses or gains electrons, becoming an ion
• Positive ion


  An atom that has lost one or more electrons, so it has more positive protons than negative electrons
• Negative ion


  An atom that has gained one or more electrons, so it has more negative electrons than positive protons
• Atoms in different groups

  • Group 1 atoms lose 1 electron
  • Group 2 atoms lose 2 electrons
  • Group 3 atoms lose 3 electrons
  • Group 5 atoms gain 3 electrons
  • Group 6 atoms gain 2 electrons
  • Group 7 atoms gain 1 electron
  • Group 0 atoms do not form ions
• Chemists normally write the charge on an ion as a superscript, a small number above the symbol
• Ionic bonding


  Bonding that occurs between metals and non-metals, where electrons are transferred
• Ionic bonding


  1. Metals need to lose electrons

  2. Non-metals need to gain electrons

  3. Oppositely charged ions are attracted by the electrostatic force of attraction

  4. The bond formed is called an ionic bond
• Fluorine cannot form an ionic bond with chlorine because they are both non-metals
• Sodium cannot form an ionic bond with magnesium because they are both metals and both need to lose electrons
• There is no electrostatic force of attraction between lithium and calcium ions because they are both positive
• When sodium reacts with chlorine to form sodium chloride

  1. Sodium loses an electron

  2. Chlorine gains an electron

  3. Oppositely charged ions are attracted by the electrostatic force
• Giant ionic lattice


  A giant structure formed when oppositely charged ions are attracted to each other in all directions
• Sodium chloride is a giant ionic lattice made of positive sodium ions and negative chloride ions
• The ions in a giant ionic lattice are held together by the electrostatic force of attraction
• The electrostatic force acts in all directions, allowing a giant lattice structure to form
• Sodium fluoride contains sodium ions (Na+) and fluoride ions (F-)
• When sodium reacts with chlorine

  1. Sodium loses an electron

  2. Chlorine gains an electron
• When aluminium reacts with chlorine

  1. Aluminium loses 3 electrons

  2. Chlorine gains 1 electron
• Aluminium chloride contains aluminium ions (Al3+) and chloride ions (Cl-)
• Magnesium chloride contains magnesium ions (Mg2+) and chloride ions (Cl-)
• When magnesium reacts with chlorine

  1. Magnesium loses 2 electrons

  2. Chlorine gains 1 electron
• Potassium forms an ionic compound with sulfur
• When two potassium atoms react with one sulfur atom

  1. Potassium loses 1 electron each

  2. Sulfur gains 2 electrons
• The ions formed are potassium ions (K+) and sulfide ions (S2-)
• High melting and boiling points of ionic compounds

  Require a lot of energy to break the strong ionic bonds
• Ionic compounds conduct electricity when liquid or in solution


  The charged ions are free to move and carry charge
• NaCl has a high melting point because it requires a lot of energy to break the strong ionic bonds
• How NaCl is formed

  1. Sodium loses an electron

  2. Chlorine gains an electron
• Potassium fluoride has a high melting and boiling point due to its strong ionic bonds
• Potassium has 19 protons, oxygen has 8 neutrons
• Oxygen ions take a 2- charge because they gain 2 electrons to fill their outer shell