An ion with the mass number 37 possesses one unit of negative charge. If the ion contains 11.1% more neutrons than protons, what is the symbol of the ion?

Let x be the number of protons.
The number of neutrons is x + 0.111x = 1.111x.
The number of electrons is x + 1 (since it has one unit of negative charge).
The mass number is 37. It is equal to the sum of the number of protons and the number of neutrons.
x + 1.111x = 37
2.111x = 37
x = 17.52 ≈ 17
The number of protons is approximately 17.
The number of neutrons is approximately 1.111 * 17 = 18.887 ≈ 19
The number of electrons is 17 + 1 = 18.
Hence, the symbol of the ion is $^{37}_{17}Cl⁻$.