Science 11

• Ions


  Atoms or groups of atoms that have positive or negative charge
• Formation of ions


  1. Atoms lose or gain electrons

  2. Atoms attain stability by following the Octet rule
• Cation


  Positively charged ion formed when an atom loses electrons
• Anion


  Negatively charged ion formed when an atom gains electrons
• Lewis Electron Dot Structure (LEDS)


  Representation of an element's symbol and its valence electrons
• Writing chemical formula of ionic compounds


  Based on the charges of the ions formed
• Sodium (Na) and Chlorine (Cl)


  • Sodium loses 1 electron to become a cation
  • Chlorine gains 1 electron to become an anion
  • Sodium and Chloride ions form sodium chloride (NaCl)
• Chlorine


  Becomes stable when it accepts the one (1) valence electrons given by Sodium
• Cation


  An atom that loses electrons becomes a positively charged ion
• Anion


  An atom that gains electrons becomes a negatively charged ion
• Lewis Electron Dot Structure (LEDS)

  Introduced by Gilbert N. Lewis, an American Physical Chemist, composed of the symbol of the element and dots which represent the number of valence electrons of an atom that can easily be determined through the group/family number in the Periodic Table of Elements
• LEDS Diagram of Sodium

  • Na
• LEDS Diagram of Chlorine


  • Cl
• Sodium (Na) transfer its electron to Chlorine (Cl)

  1. Na+ (Sodium ion, cation)

  2. Cl- (Chlorine ion, anion)

  3. NaCl (Sodium Chloride)
• Writing Chemical Formula of Ionic Compounds

  Identify the cation and write its symbol and charge, identify the anion and write down its symbol and charge, then write the symbol of the ions to form the compound
• Crisscross method


  Cross the value of charge of each ion to become subscript, the positive and the negative sign will be omitted, reduce the number of the charges to lowest term and leave out all subscripts that are 1