Formation of ions

• What is an ion?

  A charged particle
• How are ions formed?

  Atoms gain or lose electrons
• Why do atoms form ions?

  To have a full outer shell for stability
• What does the group number in the periodic table indicate?

  Electrons in the outermost shell
• How many electrons do group one elements have in their outermost shell?

  One electron
• How many electrons do group two elements have in their outermost shell?

  Two electrons
• Why are group one elements likely to form ions?

  They only need to lose one electron
• What type of ions do group one elements form?

  One plus ions
• What type of ions do group two elements form?

  Two plus ions
• How do group six elements become ions?

  They gain two electrons to become two minus ions
• How do group seven elements become ions?

  They gain one electron
• Why do elements in groups three, four, and five rarely form ions?

  They require a lot of energy to lose or gain electrons
• What is an example of a chemical equation showing ion formation for sodium?

  Na → Na⁺ + e⁻
• What is an example of a chemical equation showing ion formation for chlorine?

  Cl + e⁻ → Cl⁻
• How do we represent the formation of a magnesium ion?

  Mg → Mg²⁺ + 2e⁻
• How do we represent the formation of an oxygen ion?

  O + 2e⁻ → O²⁻
• What are the key points about ion formation from the periodic table?

  • Group number indicates outermost electrons
  • Group 1: Lose 1 electron (1+ ion)
  • Group 2: Lose 2 electrons (2+ ion)
  • Group 6: Gain 2 electrons (2- ion)
  • Group 7: Gain 1 electron (1- ion)
  • Groups 3, 4, 5: Rarely form ions due to high energy requirement
• How do we write equations for ion formation?

  • Positive ions: Electron on right
  • Negative ions: Electron on left
  • Example for sodium: Na → Na⁺ + e⁻
  • Example for chlorine: Cl + e⁻ → Cl⁻