The stability of Sc with respect to alpha, β+, and β- decay is to be determined. Do not consider the possibility of decay by electron capture. The following atomic masses are known:
He: 4.002603 u
K: 42.960717 u
Ca: 46.954543 u
Sc 46.952409 u
Ti: 46.951764 u
The
Sc nuclide is
A) not subject to alpha, β+, or β- decay.
B) subject to alpha decay only.
C) subject to β+ decay only.
D) subject to β- decay only.
E) subject to β+ or β- decay, but not to alpha decay.

Question

The stability of  Sc with respect to alpha, β+, and β- decay is to be determined. Do not consider the possibility of decay by electron capture. The following atomic masses are known: 
He: 4.002603 u 
K: 42.960717 u 
Ca: 46.954543 u 
Sc 46.952409 u 
Ti: 46.951764 u
The 
Sc nuclide is
A) not subject to alpha, β+, or β- decay. 
B) subject to alpha decay only. 
C) subject to β+ decay only. 
D) subject to β- decay only. 
E) subject to β+ or β- decay, but not to alpha decay.

Quizplus · Accepted Answer

The atomic mass of 11ea98f3_0ff8_0a33_99aa_03368f8d9837_TB2997_11
Ti is slightly less than the atomic mass of 11ea98f3_0ff8_0a34_99aa_cb15342032f4_TB2997_11
Sc. This indicates that beta minus decay is favourable, as a neutron is converted into a proton and an electron, which is emitted. Alpha decay is not possible as the nuclide is not heavy enough. Beta plus decay is also not possible as it would require the existence of a lighter and stable isotope of Sc, which does not exist. Therefore, the correct answer is D, which states that the nuclide is subject to beta minus decay only.

The Stability of Sc with Respect to Alpha, β