2.1.3 Compounds, Formulae & Equations

• What are ionic compounds formed from?

  A metal and a non-metal bonded together
• Why are ionic compounds electrically neutral?

  Because the positive charges equal the negative charges
• What type of ions do all metals form?

  Positive ions
• What charges do metals in Group 1, Group 2, and Group 3 have?

  Group 1 has 1+, Group 2 has 2+, and Group 3 has 3+
• Why are Roman numerals used in compounds formed from transition elements?

  To indicate the charge (or oxidation state) of metal ions
• What is the charge of the copper ion in copper(II) oxide?

  2+
• What is the charge of the copper ion in copper(I) nitrate?

  1+
• What suffix do non-metal ions in groups 15 to 17 have?

  ‘ide’
• What charge do elements in group 17 have?

  1. charge
• What charge do elements in group 16 have?

  1. charge
• What charge do elements in group 15 have?

  1. charge
• What are polyatomic negative ions?

  Negative ions made up of more than one type of atom
• How do the charges of simple ions depend on their position?

  They depend on their position in the Periodic Table
• How do you determine the formula for magnesium chloride?

  • Magnesium has a charge of 2+ (Group 2)
  • Chlorine has a charge of 1- (Group 17)
  • Two chloride ions are needed for each magnesium ion
  • Formula: MgCl₂
• How do you determine the formula for iron(III) oxide?

  • Iron has a charge of 3+ (indicated by Roman numeral)
  • Oxygen has a charge of 2- (Group 16)
  • Two iron ions and three oxide ions balance the charges
  • Formula: Fe₂O₃
• How do you determine the formula for aluminum nitrate?

  • Aluminum has a charge of 3+ (Group 13)
  • Nitrate is a polyatomic ion with a charge of 1-
  • The formula is based on balancing the charges
  • Formula: Al(NO₃)₃
• What is the process for determining the formula of ionic compounds?

  1. Identify the charges of the ions involved
  2. Balance the total positive and negative charges
  3. Write the formula using the appropriate subscripts
• How do the charges of simple ions depend on their position in the Periodic Table?

  The charges are determined by the group in which the element is located
• What is the formula for magnesium chloride?

  • Magnesium has a charge of 2+
  • Chlorine has a charge of 1-
  • Formula: MgCl₂
• What is the formula for iron(III) oxide?

  • Iron has a charge of 3+
  • Oxygen has a charge of 2-
  • Formula: Fe₂O₃
• What is the formula for aluminum nitrate?

  • Aluminum has a charge of 3+
  • Nitrate is a polyatomic ion with a charge of 1-
  • Formula: Al(NO₃)₃
• What is a polyatomic ion?

  An ion that contains more than one type of element
• What is a symbol equation in chemistry?

  A shorthand way of describing a chemical reaction using chemical symbols
• What is a word equation in chemistry?

  A longer way of describing a chemical reaction using only words
• Why must chemical equations be balanced?

  Because atoms cannot be created or destroyed during a reaction
• What are the steps to balance a chemical equation?

  1. Write the formulae of the reactants and products
  2. Count the numbers of atoms in each reactant and product
  3. Balance the atoms one at a time
  4. Use appropriate state symbols
• What do the state symbols (s), (l), (g), and (aq) represent?

  (s) solid, (l) liquid, (g) gas, (aq) aqueous
• What happens to ionic compounds in aqueous solutions?

  They dissociate into their ions
• What are spectator ions?

  ions that do not take part in the reaction
• What does an ionic equation show?

  Only the ions or particles taking part in a reaction