ionic bonding

• ionic bonds are formed by the transfer of electrons between atoms to produce cations (positive ions) and anions (negative ions)
• • an ionic bond is a strong electrostatic attraction between oppositely charged ions
  • they occur between metals and non-metals
  • oppositely charged ions are strongly attracted to each other, so strong bonds are formed
• dot and cross diagram of sodium and chlorine atoms

  
• dot and cross diagram of sodium chloride as ions

  
• an ion is an atom or group of atoms with a positive or negative charge
• ions form when atoms lose or gain electrons to obtain a full outer shell of electrons to form a stable electron configuration
• metals lose electrons to form cations (positive ions)
• non-metals gain electrons to form negative ions (anions)
• formation of cations:

  • metals lose electrons because number of electrons in outer shell is closer to 0 than 8
  • requires less energy to lose electrons than to gain
  • fewer electrons than protons so positively charged

  example:

  • sodium atom = 2.8.1
  • sodium ion = 2.8
• formation of anions:

  • non-metals gain electrons because number of electrons in outer shell is closer to 8 than 0
  • requires less energy to gain electrons than lose
  • more electrons than protons so negatively charged

  example:

  • oxygen atom = 2.6
  • oxygen ion = 2.8
• calculate the numbers of protons, neutrons and electrons in simple ions given the atomic number and mass number:

  • proton = atomic number
  • neutron = mass number - atomic number
  • electron = atomic number +/- charge of ion
• group 1 elements:

  • produce 1+ ions
  • 1 electron in outer shell
  • lose 1 electron for full outer shell
  • more protons than electrons
• group 2 elements:

  • produce 2+ ions
  • 2 electrons in outer shell
  • lose 2 electrons for full outer shell
• group 6 elements:

  • produce 2- ions
  • 6 electrons in outer shell
  • gain 2 electrons for full outer shell
  • more electrons than protons so negatively charged
• group 7 elements:

  • produce 1- ions
  • 7 electrons in outer shell
  • gain 1 electron for full outer shell
• a compound ends with -ide when it is a combination of two elements or a metal and non-metal
• an ionic compound is overall neutral because of same numbers of positive and negative charges bonded together
• a compound ends with -ate when it contains three or more elements, one of which is oxygen
• polyatomic ions are formed from groups of atoms that are bonded together by covalent bonds
• • hydroxide = OH (-)
  • nitrate = NO3 (-)
  • carbonate = CO3 (2-)
  • sulfate = SO4 (2-)
  • ammonium = NH4 (+)
• halides:

  • fluoride = F-
  • chloride = C-
  • bromide = Br-
  • iodide = I-
• • the structure of ions in an ionic compound in its solid state is an ionic lattice
• ionic lattice: the regular arrangement of ions in a solid ionic substance
• the ionic lattice has:

  • a regular arrangement of ions in fixed positions
  • held together by strong electrostatic forces of attraction (ionic bonds) between oppositely-charged ions
  • therefore high melting/boiling points
  • because electrostatic forces of attraction require a lot of energy to overcome