Question

Atomic masses of ${}_7^{14}N$ and ${}_8^{16}O$ are $14.008$ amu and $16.000$ amu respectively. The mass of ${}_1^{1}H$ atom is 1.007825 amu and the mass of neutron is $1.008665$ amu. Pick the correct option

• A. ${}_7^{14}N$ is more stable than ${}_8^{16}O$
• B. ${}_8^{16}O$ is more stable than ${}_7^{14}N$
• C. Both are not stable
• D. Both are equally stable

Answer 1

The correct option is B ${}_8^{16}O$ is more stable than ${}_7^{14}N$

Mass of 7 protons and 7 neutrons=$7(1.007825+1.008665)=14.11543amu$

Mass of ${}_7^{14}N=14.008amu$

Hence mass lost as energy in formation of nitrogen atom=$0.10743amu$

Mass of 8 protons and 8 neutrons=$8(1.007825+1.008665)amu=16.13192amu$

Mass of ${}_8^{16}O=16.000amu$

Hence mass lost as energy in formation of oxygen atom=$0.13192amu$

Since more mass has been lost in formation of oxygen atom, oxygen atom is more stable.