In my school planner (where our homework and our detentions are written) there is a periodic table of elements and 4

Question: In my school planner (where our homework and our detentions are written) there is a periodic table of elements and 4 elements do NOT have an atomic number. The 4 elements are Polonium, Astatine, Radon and Francium. is it a printing mistake or is there a REAL logic towards it?
- Keywords:
  elements,
  subatomic
Asked by p09bilalo to Emma, Jimmy, Janet, Niall, Simon on 18 Mar 2013.
- Niall Crawford answered on 18 Mar 2013:
  
  They all have atomic numbers – Po 84, At 85, Rn 86, and Fr 87. Sounds like a mistake…
  
  http://en.wikipedia.org/wiki/File:Periodic_table.svg

Question: In my school planner (where our homework and our detentions are written) there is a periodic table of elements and 4 elements do NOT have an atomic number. The 4 elements are Polonium, Astatine, Radon and Francium. is it a printing mistake or is there a REAL logic towards it?