1. Inspite of the fact that the third energy level in an atom contains a d- -orbital. why does the "d-- -block" start in the fourth row of the periodic table? 2. For the elements of the s---block, how is the row number related to the principal energy level or principal quantum number (n) in their electron configuration?
3. Explain why the "f-- -block" does not appear until the 6^th row, though the fourth energy level in an atom contains a "f---orbital"?
4. For the elements of the f-- -block, how is the row number related to the principal energy level or principal quantum number (n) in the electron configuration?