Question

Isotopes and isobars are two important concepts in nuclear chemistry that help us understand the behaviour of elements. Isotopes are variants of the same element that have the same number of protons but different numbers of neutrons, resulting in different atomic masses. For example, carbon-12 and carbon-14 are isotopes of carbon, with six protons but different neutron counts. In contrast, isobars are atoms of different elements that have the same mass number but different atomic numbers, meaning they contain different numbers of protons and neutrons. An example of isobars includes argon-40 and calcium-40, both having a mass number of 40 but differing in their elemental identity. Understanding isotopes and isobars is crucial in fields such as radiocarbon dating, nuclear medicine, and understanding the stability of atomic nuclei.

In a sample of ethyl ethanoate (CH₃COOC₂H₅) the two oxygen atoms have the same number of electrons but different number of neutrons. Which of the following is the correct reason for it?