Development of the Periodic Table

• How did Dmitri Mendeleev's periodic table predict the properties of elements?

  By arranging elements and leaving gaps for undiscovered ones
• What is the structure of the modern periodic table?

  It is arranged into columns called groups
• What does the term "periodic" mean in the context of the periodic table?

  It means occurring at regular intervals
• Which group consists of highly reactive metals?

  Group one
• Which group consists of highly reactive nonmetals?

  Group seven
• Why do elements in the same group have similar chemical properties?

  Because they have the same number of electrons in their outer energy level
• Who was the scientist that noticed elements with similar properties occurred in threes?

  Johan Dobereiner
• What did Dobereiner call the groups of three elements with similar properties?

  Triads
• What did John Newlands observe about the elements when arranged by atomic weight?

  Every eighth element reacted in a similar way
• What is Newlands' law of octaves?

  It states that every eighth element has similar properties
• What was a major problem with Newlands' system of arranging elements?

  Elements were sometimes grouped together with different properties
• Who developed the first modern periodic table?

  Dmitri Mendeleev
• How did Mendeleev arrange the elements in his periodic table?

  In order of increasing atomic weight
• What unique approach did Mendeleev take when arranging elements?

  He switched the order of specific elements to fit patterns
• What did Mendeleev do when he encountered undiscovered elements?

  He left gaps in his periodic table
• What did Mendeleev predict about the undiscovered elements?

  He predicted their properties based on other elements in the same groups
• What was the outcome when the missing elements were discovered?

  Their properties matched Mendeleev's predictions
• How is the modern periodic table different from Mendeleev's table?

  It is arranged by atomic number instead of atomic weight
• What is the atomic number?

  The number of protons in an element
• Why is ordering by atomic weight problematic?

  Elements can appear in the wrong order due to isotopes
• Which two elements are examples of those that can be misordered by atomic weight?

  Thorium and iodine
• What does the modern periodic table include that Mendeleev's did not?

  Group zero, the noble gases
• What can students find plenty of questions on this topic?

  In the vision workbook