The perodic table is divided into 18 columns and 7 rows. The columns are called groups and the rows are called periods.
Then, if we see a periodic table, we have to search first the group, in this case 18.
This is the group that we are looking for, it is called the noble gases group.
Then, we only have to count which one is the number 4.
If we count, we will have that our element is Kr (krypton).