Chemical formulae of ions

• What do chemists use to represent elements and compounds?

  Symbols and formulae
• What do word equations and balanced chemical equations represent?

  The changes that happen in chemical reactions
• What is an ion?

  An electrically charged particle formed when an atom or molecule gains or loses electrons
• How is an ion formed?

  When an atom or a group of atoms loses or gains electrons
• What is the charge of an electron?

  Negative
• What does the superscript in a chemical formula indicate?

  The number and sign of its electrical charges
• What are the names and formulas of some common ions?

  • Sodium: Na⁺, One positive
  • Magnesium: Mg²⁺, Two positive
  • Chloride: Cl^-, One negative
  • Oxide: O^2-, Two negative
• What is an ionic compound?

  An ionic compound occurs when a negative ion joins with a positive ion
• How can the formula of an ionic compound be predicted?

  Using the formulae of its ions
• What must the numbers of ions in a formula provide?

  An equal number of positive and negative charges
• What are the formulas and electrical charges of some common ionic compounds?

  • Sodium chloride: NaCl, One positive, one negative
  • Sodium oxide: Na₂O, Two positive, two negative
  • Magnesium oxide: MgO, Two positive, two negative
  • Magnesium chloride: MgCl₂, Two positive, two negative
• What is the formula for sodium chloride?

  NaCl
• What is the formula for sodium oxide?

  Na₂O
• What is the formula for magnesium oxide?

  MgO
• What is the formula for magnesium chloride?

  MgCl₂