Doubt from atomic structure

atomic-structure
find-group-period
periodic-properties
easy
unsolved
pp
#1

In an atom the last electron is present in f-orbital and for its outermost shell the graph of (Psi) ^2 has 6 maximas. What is the sum of group and period of that element?
Ans =9

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#2

The last electron is present in f orbital
=> group number = 3

Since the last electron is in f-orbital
=>the penultimate shell will be s-orbital

psi^2 graph for Outermost shell (here s) gives 6 maxima
=> Number of nodes = 6-1 = 5

now apply the formula
n-l-1 =number of nodes,
l = 0 for S-orbital

=> n-l-1 = 5
=> n-1=5
=> n=6

So answer is 6+3= 9

#3