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period 6
The element that has 86 protons in period 6 is Radon (Rn).
Chromium is the element in period 4 and group 6.
There is no element in period 3 group 6. The element at period 3, group 16 (called on very old periodic tables group VIA) is sulfur (S).
Caesium is a Period 6 element.