Periodic Table

• Why is the periodic table called the periodic table?

  Because similar properties occur at regular intervals.
• What are the names of the columns in the peiodic table and why elements are placed in the same column?

  Elements in the same group in the periodic table have the same number of electrons in their outer shell (outer electrons) and this gives them similar chemical properties.
• How is the position of an element in the periodic table related to the arrangement of electrons in its atoms and its atomic number.

  An element's position on the periodic table is directly related to its atomic number, which represents the number of protons in its nucleus, and consequently, the arrangement of electrons in its electron shells.
• State how scientists initially classified elements.

  Scientists attempted to classify the elements by aranging them in order of their atomic weights.
• Describe problems with the early periodic table

  • They were incomplete
  • Some elements were placed in inappropriate groups if the strict order of atomic weights was folllowed
• How did Mendeleev overcome initial problems with the early periodic table?

  • Left gaps for elements he thought had not been discovered
  • In some places, changed the order of the periodic table based on atomic weights.
• How was Mendeleev's new periodic table proved to be right?

  Elements with properties predicted by Mendeleev were discovered and filled the gaps.
• Why was the initial order of the periodic table, based on atomic weight, proved to not always be correct?

  • Isotopes
  • which are atoms of the same element with different atomic masses, meaning that sometimes an element with a lower atomic number could have a higher atomic mass than an element with a higher atomic number, causing a mismatch in the order.