Ch 6 Chemical Formulae and Equations

• What are monoatomic elements?


  -elements that exist as uncombined atoms

  -elements in group 18

  -> unreactive -> full valence shell of electrons
• What are diatomic molecules?


  molecules that exist as 2 chemically combined atoms
• What are some examples of elements that exist as diatomic molecules?

  -Hydrogen - H2

  -Oxygen - O2

  -Nitrogen - N2

  -Fluorine - F2

  -Chlorine - Cl2

  -Bromine - Br2

  -Iodine - I2
• 'ne' - 2 of the same element
• What are polyatomic molecules?

  molecules that exist as 3 or more chemically combined atoms
• What are some examples of elements that exist as polyatomic molecules?

  ammonia - NH3

  copper (II) sulfate - CuSO4

  sodium hydroxide - NaOH

  hydrochloric acid - HCl

  ethanoic acid - CH3COOH
• What are some examples of positive ions?

  Hydrogen - H+

  Ammonium - NH4+

  Silver - Ag+

  Zinc - Zn 2+
• List some examples of negative ions

  Hydroxide - OH-

  Nitrate - NO3-

  Carbonate - CO3 2-

  Sulfate - SO4 2-

  Sulfite - SO3 2-

  Phosphate - PO4 3-
• Zinc and silver are in the transition metal block - form an only / common ion each with fixed valences

  Zinc - Zn 2+

  Silver - Ag +
• How can chemical equations be balanced?

  -Atoms are conserved in physical and chemical reactions

  -> every atom on the left-hand side of the arrow must also appear on the right-hand side

  -> number of atoms on the left = number of atoms on the right
• What are ionic equations?


  -Show ions that take part in reactions

  -involve at least 1 aqueous reactant (usually an ionic compound)

  -constructed from balanced chemical equations
• What are spectator ions?

  -Substances that appear on both left and right side of the equation remain unchanged in their physical state or their charge do not take part in the reaction

  -removed from the ionic equation
• What are the ions of HBr (aq)?

  H+ (aq) + Br - (aq)
• What are the ions of 3AlCl3 (aq)?

  3Al 3+ (aq) + 9Cl - (aq)
• What are the ions of 2NH4OH (aq)?

  2NH4+ (aq) + 2OH- (aq)
• What are the ions of 3MgSO4 (aq)(aq)?

  3Mg 2+ (aq) + 3SO4 2- (aq)
• What are the 3 main types of aqueous substances?

  -ionic substances -> can be split into ions

  -Acids -> split into H+ and another ion

  -Diatomic molecules -> cannot be split into ions
• What are the different state symbols?

  (s) solid

  (l) liquid

  (g) gas

  (aq) aqueous
• Relative molecular mass VS Relative formula mass

  "molecular mass" is used for covalent molecules

  "formula mass" is used for ionic compounds
• What is the formula for percentage mass?

  Percentage mass = [ ( number of atoms in an element in a formula * relative atomic mass of element ) / Relative molecular mass of compound ] * 100%