Answer:
HELIUM
Explanations;
The smallest element in the periodic table can be categorized based on the value of its atomic radius.
In the periodic table, the atomic radius of elements increases as we move down the table and decreases as we move from left to right.
The increment of the radius from top to bottom is mainly due to the increase in the atomic number due to the increase in the electron shells.
Since the Helium element has the smallest atomic radius, we can categorize it as the smallest element in the periodic table.
In conclusion, the smallest element if categorized based on the atomic radius will be HELIUM