Question

a particular atom of an element has 18 protons, 22 neutrons, and 18 electrons. which characteristics determine its identity

Answer 1

The number of protons determine its identity

Answer 2

Number of Protons

explanation: with elements on the periodic table, the number of protons always equals which order it goes in on the table.
e.g, Hydrogen is the first element on the periodic table which means it has one proton.
TL;DR
number of protons determines Element name/identity

i hope that helped :)