Which of the following statement(s) is/are correct about the isotopes of an elements? They have the same I…

Analyze the question: We need to decide which statements are true about isotopes of the same element.

Concept: Isotopes are atoms of the same element with the same number of protons (atomic/proton number) but different numbers of neutrons. Because the neutron number differs, their mass numbers (nucleon numbers) differ.

Checking each statement:

• I. Same chemical properties: TRUE. Chemical behaviour depends on the number and arrangement of electrons, which equals the number of protons in a neutral atom. Isotopes have the same electron configuration, so they react chemically in the same way.
• II. Same nucleon number: FALSE. Nucleon number = protons + neutrons. Isotopes have different numbers of neutrons, so their nucleon numbers differ. (For example, carbon-12 and carbon-14 have nucleon numbers 12 and 14.)
• III. Same proton number: TRUE. This is what defines an element, so all isotopes of it share the same proton number.

Conclusion: Statements I and III are correct, so the answer is D. I and III only.

Tip: Remember "Isotopes = Isotopic protons": same Proton number and same Chemical properties, but different Neutron and nucleon numbers. Think "P and C same, N different."