Ions and ionic bonding

• Ion


  A charged particle, could be a single atom or a group of atoms
• How ions are made

  1. Atoms gain or lose electrons

  2. To have a full outer shell

  3. To be more stable
• Group number


  Tells us how many electrons the atoms of that group have in the outermost shell
• Atoms need to lose or gain electrons until their outermost shell is full
• Losing and gaining electrons requires energy
• Atoms that only have to lose or gain one or two electrons


  • Are much more likely to form ions
  • Because it requires less energy
• Group 1 elements (alkaline metals)


  • Easily lose one electron to become one plus ions
• Group 2 elements


  • Easily lose two electrons to become two plus ions
• Group 6 elements


  • Easily gain two electrons to become two minus ions
• Group 7 elements


  • Easily gain one electron
• Elements in groups 3, 4 and 5 would have to lose or gain 3 or 4 electrons, which requires a lot of energy
• We generally don't see elements in groups 3, 4 and 5 as ions
• Equation to show gain or loss of electrons

  1. Atom goes to form ion plus electron (if losing electrons)

  2. Atom plus electron goes to form ion (if gaining electrons)
• Sodium


  • Sodium atom goes to form sodium ion plus electron
• Chlorine


  • Chlorine plus electron goes to form chloride ion
• Ionic bonds


  Bonds formed between atoms with opposite charges due to electrostatic forces
• Ions


  Atoms that have lost or gained electrons, forming a positive or negative charge
• Magnesium


  • Magnesium goes to form magnesium two plus ion plus two electrons
• Formation of ions


  1. Atom loses electron to become positive ion

  2. Atom gains electron to become negative ion
• Oxygen


  • Oxygen plus two electrons goes to form oxygen two minus ion
• Ions


  • Sodium one plus ion
  • Chloride one minus ion
• Atoms with too many electrons

  Transfer electrons to atoms that don't have enough
• Ionic compound


  Compound formed by the attraction between oppositely charged ions
• Dot and cross diagram


  Diagram showing the arrangement of electrons in a compound, with one atom's electrons as dots and the other as crosses
• Dot and cross diagrams show the movement of electrons with an arrow
• Dot and cross diagrams can show either the full electron shells or just the outermost shells
• Formation of magnesium chloride (MgCl2)

  1. Magnesium has 2 outer electrons to donate

  2. Chlorine has 7 outer electrons, needs 1 more each

  3. Magnesium donates 1 electron to each chlorine

  4. Resulting in a magnesium two plus ion and two chloride one minus ions

  5. Ions arranged with chlorides on either side of magnesium
• Ionic bonds are strong, similar in strength to covalent bonds
• Ionic bonding


  A metal atom transfers one or more electrons to a non-metal atom to form two oppositely charged ions, which are then attracted to each other by electrostatic forces
• Ionic compounds


  • Involve tons of ions, not just a couple
  • Positive and negative ions alternate so each ion is attracted to all those around it
  • Form three-dimensional regular lattice structures
• Properties of ionic compounds

  • Have very high melting and boiling points
  • Can conduct electricity when melted or dissolved in water, but not in solid form
• Melting and boiling points of ionic compounds

  Determined by the strength of the ionic bonds holding the substance together
• Electrical conductivity of ionic compounds

  Depends on the presence of charged particles (ions or electrons) that are free to move
• Determining the formula of an ionic compound

  1. Identify the charges of the ions

  2. Balance the charges to form a neutral compound

  3. Determine the simplest whole number ratio of the ions
• Common polyatomic ions


  • Hydroxide (OH-)
  • Sulfate (SO4^2-)
  • Nitrate (NO3-)
  • Carbonate (CO3^2-)
  • Ammonium (NH4+)