Medium
The table shows four species:
W: 6 protons, 6 neutrons
X: 7 protons, 7 neutrons
Y: 6 protons, 8 neutrons
Z: 8 protons, 8 neutrons
Which two species are isotopes of the same element?
Explanation
Explanation
Step 1: The identity of an element is fixed by its number of protons (atomic number).
Step 2: Isotopes are atoms of the same element, so they have the same number of protons but different numbers of neutrons (different mass numbers).
Step 3: Compare: W and Y both have 6 protons (carbon), but W has 6 neutrons (mass number 12) and Y has 8 neutrons (mass number 14).
Step 4: X (7 protons) and Z (8 protons) differ in protons, so they belong to different elements.
Answer: W and Y.
PRO TIP
Re-check your working by substituting the answer back into the original question.