Question

In a sample of ethyl ethanoate $\left(C{H}_{3}COO{C}_2{H}_5\right),$ 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?

• A. One of the oxygen atoms has gained electrons
• B. One of the oxygen atoms has gained two neutrons
• C. The two oxygen atoms are isotopes
• D. The two oxygen atoms are isobars.

Answer 1

Answer: (C)

The two oxygen atoms are isotopes

Isotopes are atoms of the same element having same atomic number but different mass number.

As number of electrons and number of protons are equal in an atom, different mass number means different number of neutrons.

Oxygen has three isotopes namely, ${}_8^{16}O$ ${}_8^{17}O$ ${}_8^{18}O$. In $C{H}_{3}COO{C}_2{H}_5$, both have same number of electrons therefore atomic number is same so they are isotopes.

Both have different number of neutrons so the atomic mass of both are different. This also shows that they are isotopes of each other.

Hence the correct options are B and C.