Development of the periodic table C1

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

  Early attempts to arrange the elements into a periodic table
• How did Dmitri Mendeleev's periodic table predict the properties of elements?

  By arranging elements in order of increasing atomic weight and leaving gaps for undiscovered elements
• What is the modern periodic table arranged into?

  Columns called groups
• What does the term "periodic" mean in the context of the periodic table?

  Occurring at regular intervals
• Which groups are mentioned in the periodic table?

  Group one, group two, transition elements, groups three to seven, and group zero
• What types of elements are found in group one of the periodic table?

  Highly reactive metals such as lithium, sodium, and potassium
• What types of elements are found in group seven of the periodic table?

  Highly reactive nonmetals such as fluorine, chlorine, and bromine
• 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 first noticed elements with similar properties occurred in threes?

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

  Triads
• Which three metals did Döbereiner use as an example of triads?

  Lithium, sodium, and potassium
• Which three nonmetals did Döbereiner use as an example of triads?

  Chlorine, bromine, and iodine
• What did John Newlands observe when he arranged elements by increasing atomic weight?

  Every eighth element reacted in a similar way
• What did Newlands call his observation about the elements?

  His law of octaves
• What was a problem with Newlands' law of octaves?

  Elements were sometimes grouped together with totally 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 two unique actions did Mendeleev take when creating his periodic table?

  He switched the order of specific elements and left gaps for undiscovered elements
• What did Mendeleev predict about the undiscovered elements?

  Their properties based on other elements in the same groups
• What is a significant difference between Mendeleev's table and the modern periodic table?

  The modern periodic table is arranged by atomic number instead of atomic weight
• Why is ordering by atomic weight problematic?

  Elements can appear in the wrong order due to the presence of isotopes
• Which two elements are mentioned as examples of isotopes causing issues in ordering 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 you find plenty of questions on the periodic table topic?

  In the vision workbook
• What are the key features of the modern periodic table?

  • Arranged by atomic number
  • Organized into groups (columns)
  • Includes group zero (noble gases)
  • Elements with similar properties occur at regular intervals
• What are the historical developments leading to the modern periodic table?

  1. Döbereiner's triads
  2. Newlands' law of octaves
  3. Mendeleev's arrangement by atomic weight
  4. Gaps for undiscovered elements
  5. Modern arrangement by atomic number