Electronic Structure and History of the Periodic Table

• Who discovered that the plum pudding model was wrong?

  Ernest Rutherford
• Who first devised an experiment that proved the existence of the neutron?

  James Chadwick
• What is the electronic structure of sodium?

  [2, 8, 1]
• Why did Mendeleev leave gaps in his Table of Elements?


  Mendeleev left gaps in his table to place elements not known at the time