Bonding

• Ionic bonds


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


  Atoms that have lost or gained electrons, becoming charged particles
• Formation of ions


  1. Atom loses electrons to become a positive ion

  2. Atom gains electrons to become a negative ion
• Sodium ion


  • Sodium atom loses 1 electron to form Na+ ion
• Chloride ion


  • Chlorine atom gains 1 electron to form Cl- ion
• Formation of ionic compounds


  1. Transfer of electrons from metal atom to non-metal atom

  2. Resulting in oppositely charged ions

  3. Ions are attracted by electrostatic forces to form ionic compound
• Dot and cross diagram

  Representation of ionic bonding showing electrons as dots and crosses
• Dot and cross diagram


  • Electrons of one atom shown as dots, other atom as crosses
  • Can show full electron shells or just outermost shell
• Magnesium chloride (MgCl2)


  • Magnesium atom donates 2 electrons to 2 chlorine atoms
  • Resulting in Mg2+ and 2 Cl- ions
  • Ions arranged to show attraction in ionic compound
• Ionic compounds


  Compounds formed by the transfer of electrons from a metal atom to a non-metal atom, resulting in oppositely charged ions that are attracted to each other
• 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
• Representation of ionic compounds


  • Ball and stick diagrams
  • Positive and negative ions
• Properties of ionic compounds


  • Have very high melting and boiling points
  • Can conduct electricity when melted or dissolved in water
• 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 can move freely
• 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
• Ionic compound formulas


  • NaCl
  • MgCl2
  • Ca(OH)2
  • Al2(SO4)3
• Important ions to know


  • Hydroxide (OH-)
  • Sulfate (SO4^2-)
  • Nitrate (NO3-)
  • Carbonate (CO3^2-)
  • Ammonium (NH4+)
• How atoms can form covalent bonds

  1. Sharing electrons

  2. Drawing covalent bonds
• Ionic bonds


  Atoms transfer electrons from one to the other, forming oppositely charged ions that are attracted through electrostatic forces
• Atoms transfer electrons to get a full outer shell
• This works when one atom has too many electrons and the other too few, like sodium and chlorine
• When two non-metal elements like two chlorine atoms need an extra electron each, they can share electrons instead of transferring them
• Dot and cross diagram

  Used to show which electrons belong to each atom when drawing covalent bonds
• Displayed formula


  Writes the chemical symbols of atoms and uses lines to show covalent bonds
• Displayed formulas are easier to draw for large molecules than dot and cross diagrams
• Displayed formulas don't show the 3D shape of the molecule
• Non-metals


  Can join together by covalent bonds in which they share electrons so that all of the atoms have full outer shells
• Drawing covalent bonding in ammonia (NH3)

  1. Draw all atoms with outermost shells

  2. Determine how atoms can fit together to have full outer shells

  3. For displayed formula, replace shells and electrons with lines showing covalent bonds
• Simple molecular substances


  • Small molecules made up of just a few conveniently bonded atoms
  • Separate molecules are only joined together by weak intermolecular forces
• Giant covalent structures


  • Made of huge numbers of non-metal atoms that are all bonded to each other by covalent bonds
  • Generally arranged into regular repeating lattices
• Covalent bonds


  Strong bonds that require a lot of energy to break apart
• Simple molecular substances


  Small molecules where atoms are joined by strong covalent bonds, but between molecules there are only weak intermolecular forces
• Covalent bonds within molecules

  Are strong
• Intermolecular forces between molecules


  Are weak
• Polymers


  Long chains made up of repeating monomer units
• Molecule size increases going down the halogen group


  • Intermolecular forces increase
  • Melting and boiling points increase
• Giant covalent structures


  Structures like silicon dioxide, diamond, and graphite, with billions/trillions of atoms joined by covalent bonds in a regular lattice
• Simple molecular substances don't conduct electricity because there are no free electrons and the molecules themselves have no electric charge</b>