bonding, structure and properties of matter

• an ion is a charged particle that has gained or lost electrons.
• an atom becomes an ion by losing or gaining one or more electrons.
• metals become positive ions
• non metals become negative ions
• noble gases do not form ions as they already have a full outer shell of electrons, so they don't need to gain or lose electrons
• types of chemical bond:

  ionic bonds, covalent bonds, metallic bonds
• an ionic bond is the strong electrostatic attraction between oppositely charged ions
• atoms form ions so that they gain a full out shell of electrons, which makes them more stable
• how an ionic bond forms between a metal atoms and a non-metal atom:


  1)the metal atom will transfer one or more electrons to the non-metal atom so that both have full outer shells. 2)this will make the metal a positive ion, and the non metal a negative ion. 3)the two oppositely charged ions will then be strongly attracted by electrostatic forces. 4)this electrostatic force of attraction=ionic bond
• an ionic compound is a compound containing positive and negative ions, help together by electrostatic forces of attraction.
• the structure of an ionic compound:


  ionic compounds have a giant ionic lattice structure. the ions form a closely-packed regular lattice arrangement, with strong electrostatic forces of attraction between oppositely charged ions in all directions.
• why are ball and stick diagrams not realistic?

  1)atoms (or ions) are not really perfect spheres. 2)they don't show the electrons. 3)the atoms are relatively far apart, whereas in reality they would be much closer
• properties of ionic compounds:


  1)high melting and boiling points. 2)conduct electricity when molten or aqueous, but not when solid. 3)brittle
• ionic compounds have high melting and boiling points because the strong ionic bonds (electrostatic forces of attraction) between the oppositely charged ions require a lot of energy, and therefore high temperature, to break.
• ionic compounds only conduct electricity when molten or dissolved in water (aqueous), but not when solid. this is because substances need charged particles that are free to move in order to conduct electricity. when ionic compounds are solid, their ions are in a fixed lattice, so can't flow. however when molten or aqueous, the ions are free to move and carry charge.
• the empirical formula is the smallest whole number ratio of atoms of each element within a compound. (for example the empirical formula for N2O4 is NO2)
• the molecular formula is a formula that shows the exact number of atoms of each element within a compound. (for example, the molecular formula for water is H2O, while ethane is C2H6)
• covalent bonds form between 2 non-metal atoms
• a covalent bond is the electrostatic attraction between a shared pair of electrons and the nuclei of the two atoms. it is formed when 2 atoms share electrons to gain a full outer shell of electrons.
• 3 ways of drawing a covalent bond:

  1)dot and cross diagram. 2)displayed formula. 3)3D models
• what 3 types of substances can covalent bonds make?

  polymers, giant covalent structures and simple molecular substances
• a polymer is a large molecule, made up of lots of smaller units called monomers
• a giant covalent structure is a structure in which all of the atoms are bonded together by strong covalent bonds
• 3 examples of giant covalent structures:

  diamond, graphite and silicon dioxide
• simple molecular substances are substances that consist of small molecules. (e.g H20 or 02)
• BOMACLATT T
• the bonding in simple molecular substances:

  in simple molecular substances, there are strong covalent bonds between the atoms of each molecule, but weak intermolecular forces between the different molecules.
• simple molecular substances have low melting and pointing points because


  although the strong covalent bonds between the atoms are very strong, the intermolecular forces between the molecules are weak, so only require a small amount of energy to break.