The vertical columns are groups
The horizontal rows are periods
Answer: Tin (Sn)
Explanation: The electron configuration for tin (Sn) is shown in the picture. It's last electrons are:
5s^2 4d^10 5p^2
The valence electrons are in the 5th electron shell and include 2 each in the 5s and 5p orbitals.
I think the answer is true.
The one that is observed or measured in the experiment, and it is known as the dependent variable.