The letter "T" is not the symbol of any chemical element on the periodic table, while "U" is the symbol for Uranium, which is a chemical element. Therefore, "T" is not a chemical element symbol but "U" is. To clarify further:
- There is no element with the symbol "T."
- The symbol "U" stands for Uranium, element number 92.
Hence, the correct answer is "T" is not a chemical element symbol, but "U" is.
