Which of the following is not a possible empirical formula? vis P_(2)O_(6) C_(5)H_(11) NO_(2)

The correct answer is: vis<br /><br />Explanation: An empirical formula represents the simplest whole-number ratio of atoms in a compound. Among the given options, $P_{2}O_{6}$, $C_{5}H_{11}$, and $NO_{2}$ are all valid empirical formulas as they represent the simplest whole-number ratios of atoms. However, "vis" is not a valid empirical formula because it does not represent a recognizable chemical compound or a valid combination of elements.