Final answer:
Isotopes of the same element have the same atomic number but different mass numbers. Deuterium (2H or D) and tritium (³H or T) are isotopes of hydrogen with one proton but different numbers of neutrons.
Step-by-step explanation:
To identify which symbols represent isotopes of the same element, we should look for symbols with the same atomic number since isotopes are atoms of the same element with different mass numbers due to a different number of neutrons.
Hydrogen is an example of an element with multiple isotopes and is unique in that its isotopes have specific names: deuterium (symbolized 2H or D) and tritium (symbolized ³H or T). Both deuterium and tritium have the same number of protons (atomic number 1) but differ in their neutron count, which results in different mass numbers.
Isotopes are always the same in the number of protons (atomic number) and always different in the number of neutrons, and therefore the mass number. When we write the symbol for isotopes, we include the mass number as a superscript and the atomic number as a subscript before the element's symbol (e.g., ²H and ³H).