Question

In a sample of ethyl ethanoate $\left({\mathrm{CH}}_3{\mathrm{COOC}}_2{\mathrm{H}}_5\right)$ 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

The correct option is C

The two oxygen atoms are isotopes.

Explanation for correct option:

Option C: The two oxygen atoms are isotopes:

1. In a sample of ethyl ethanoate $\left({\mathrm{CH}}_3{\mathrm{COOC}}_2{\mathrm{H}}_5\right)$, the two oxygen atoms have the same number of electrons but different number of neutrons.
2. Forms of same element that have same number of electrons but different number of neutrons are known as isotopes.
3. Thus, the two oxygen atoms are isotopes.

Explanation for incorrect options:

Option A: One of the oxygen atoms has gained electrons:

1. If an oxygen atom will gain electron, the number of electrons will change.
2. But both the oxygen atoms have same number of electrons.

Option B: One of the oxygen atoms has gained two neutrons:

1. An atom cannot gain neutrons.
2. This is because for the neutron to enter the nucleus high amount of energy is required.

Option D: The two oxygen atoms are isobars:

1. Isobars have same number of nucleons i.e. protons and neutrons together.
2. But here the number of neutrons are different.

The correct option is Option C.