Ionic Bonding

1.21 Explain how ionic bonds are formed by the transfer of electrons between atoms to produce cations and anions, including the use of dot and cross diagrams
  • Metal + Non-metal: electrons in the outer shell of the metal atom are transferred
    • Metal atoms lose electrons to become positively charged ions
    • Non-metal atoms gain electrons to become negatively charged ions
    • NB: Ions – Atoms that have lost or gained electron/electrons.
  • Electron transfer during the formation of an ionic compound can be represented by a dot and cross diagram (see eg for NaCl below)

1.22 Recall that an ion is an atom or group of atoms with a positive or negative charge
  • Since an ion is formed from a metal losing an electron, i.e. becoming a positive metal ion or from a non-metal gaining an electron, i.e. becoming a negative ion…an ion is an atom or group of atoms with a positive or negative charge
    • Cation = positive ion (+ -> ca+ion)
    • Anion = negative ion (Negative -> aNion)
1.23 Calculate the numbers of protons, neutrons and electrons in simple ions given the atomic number and mass number
  • Atomic number = proton number = number of protons
  • Mass number = nucleon number = number of protons + neutrons
  • In an atom number of protons = number of electrons, but in an ion, there could be more or less protons/more or less electrons (i.e. if it is a cation with a 1+ charge, it has 1 more proton than electron and if it is an anion with a 1- charge, it has 1 more electron than proton) – use this information to determine the numbers of protons, neutrons and electrons in simple ions. Number of neutrons is no different from the equivalent atom.
1.24 Explain the formation of ions an ionic compounds from their atoms, limited to compounds of elements in groups 1, 2, 6 and 7
  • Ions produced by metals in Groups 1 and 2 and by non-metals in Groups 6 and 7 have the electronic structure of a noble gas (Group 0)
1.25 Explain the use of the endings –ide and –ate in the names of compounds
  • The names of some anions end in –ate or –ide, -ate suggests the presence of oxygen in the anion, e.g. carbonate, sulfate, nitrate, with the exception of oxide (and peroxide and hydroxide) – normally more than one oxygen
1.26 Deduce the formulae of ionic compounds (including oxides, hydroxides, halides, nitrates, carbonates and sulfates) given the formulae of the constituent ions
  • Oxide -> involves O^2- ion (e.g. sodium oxide: Na2O
  • Hydroxide -> involves OH^ 1- ion (e.g. sodium hydroxide: NaOH)
  • Halide -> involves a negative halide ion (e.g. sodium chlorIDE NaCl)
  • Nitrate -> involves NO3^1- ion (e.g. sodium nitrate: NaNO3)
  • Carbonate -> involves CO3^2- ion (e.g. sodium carbonate: NaCO3)
  • Sulfate -> involves SO4^2- ion (e.g. sodium sulfate: NaSO4)
1.27 Explain the structure of an ionic compound as a lattice structure: consisting of a regular arrangement of ions; held together by strong electrostatic forces (ionic bonds) between oppositely-charged ions 
  • A giant structure of ions = ionic compound
  • Held together by strong electrostatic forces of attraction between oppositely charged ions
  • The forces act in all directions in the lattice, and this is called ionic bonding.

An example is sodium chloride (salt):

Na+ (small blue particles) and Cl- (larger green ones)