Concept:Isotopes are atoms of the same element with the same number of protons but different numbers of neutrons, leading to different mass numbers.
Explanation:Chlorine has atomic number
Z=17, meaning every chlorine atom has 17 protons.
The two common isotopes of chlorine are:
•
1735Cl (Chlorine‑35) — with
35−17=18 neutrons.
•
1737Cl (Chlorine‑37) — with
37−17=20 neutrons.
The correct isotopic notation shows the mass number (top) and atomic number (bottom) both on the left of the element symbol.
Only option D lists the isotopes as
1735Cl and
1737Cl, which matches the required notation.
Options A, B, and C either have incorrect mass numbers or mismatched atomic numbers.
Answer:Option D:
1735Cl and 1737Cl (properly written as
1735Cl and
1737Cl).