An element with 16 electrons means it has an atomic number of 16, which corresponds to the element sulfur (S). The nucleon number (mass number) of 37 indicates that this specific isotope of sulfur has 21 neutrons, since the number of neutrons can be found by subtracting the atomic number from the mass number:
\[ \text{Number of neutrons} = \text{Nucleon number} - \text{Atomic number} = 37 - 16 = 21 \]
Thus, the element you are referring to is sulfur-37 (\(^{37}\text{S}\)).