Development of the periodic table

• In the early 1800’s, how were elements arranged in the periodic table ?

  • Atomic weight
• Name given to elements in group 2 ?

  Alkaline earth metals
• Why did Mendeleev leave gaps in his table ?

  Ensure elements with similar properties stayed in the same group, and to leave space for elements that hadn’t been discovered yet.
• Why were elements often placed in the wrong group in early versions of the periodic table ?


  • Placed in order of atomic weight rather than than atomic mass, and didn’t take into account the elements chemical properties .
• How did the discovery of isotopes help to validate Mendeleev‘s periodic table ?

  • Some isotopes had different masses, but the same chemical properties - he was correct in putting them in groups with other elements that had the same chemical properties.
• Name is given to the elements in group 7 ?

  Halogens
• How did Mendeleev arrange his periodic table ?

  1. Increasing atomic mass
  2. Had similar properties into rows ( periods ), and Columns ( groups )
  3. He left gaps.
• Name given to the elements in group 1

  Alkali Metals
• Why do we use the word ‘periodic’ in the periodic table ?

  
  

  • Scientists noticed a ‘periodic‘ pattern in the properties of elements e.g a pattern that repeats
• Why are elements put into groups ?

  Group together the elements that have similar properties.
• What does the period tell you about the atoms of an element ?

  Number of shells
• What name is given to the elements in group 0 ?

  Noble gases.
• What does the group number tell you about the atoms of an element ?

  Number of electrons on outer shell.
• How are elements arranged in the modern periodic table ?

  • By increasing atomic number.
  • Patterns of chemical and physical properties ( periods/groups)