NCERT Class XII Chapter
Nuclei
Questions With Solutions

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Question : 14
Total: 31
The nucleus
23
10
Ne
decays by β emission. Write down the β decay equation and determine the maximum kinetic energy of the electrons emitted. Given that:
m (
23
10
Ne
)
= 22.994466 amu, m (
23
11
Na
)
= 22.989770 amu
Solution:  
The β decay of
23
10
Ne
may be explained as
23
10
Ne
23
11
Na
+
0
1
e
+
v
+Q

The expression or the kinetic energy released may be written as
Q = [m(
23
10
Ne
)
m(
23
11
Na
)
me
]
c2
= [m(
23
10
Ne
)
m(
23
11
Na
)
]
c2

≈ [22.994466 – 22.989770] × 931.5 MeV
≈ 0.004696 × 931.5 MeV = 4.374 MeV
As
23
11
Na
is massive, the kinetic energy released is mainly shared by electron-positron pair. When the neutrino carries no energy, the electron has a maximum kinetic energy equal to 4.374 MeV.
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