If an orbital could contain3 electron total number of groups in periodic table would have been :
a. 20
b. 27
c. 36
d. 42

In existing periodic table there are 2 s orbital 6 p orbital and 10 d orbital constituting the 18 grps ( f is outside) .So when one electron increases s block grps become 3 p block become 9 and d block become 15 . ...Therefore total is 27