Development of the Periodic Table

• What should you be able to describe by the end of the video?

  Early attempts to arrange elements into a periodic table.
• What does the term "periodic" mean in the context of the periodic table?

  Occurring at regular intervals.
• How are elements arranged in the modern periodic table?

  • Arranged into columns called groups
  • Group one and two are followed by transition elements
  • Groups three to seven and group zero (noble gases)
• Why do elements in the same group have similar chemical properties?

  Because they have the same number of electrons in their outer energy level.
• What did Johan Dober notice about elements with similar chemical properties?

  They often occurred in threes, which he called Triads.