In the reaction above, X is
The sum of the mass numbers on the right-hand side = that on the left-hand side
Also, the sum of the atomic numbers on the right-hand side = that on the left-hand side.
Sum of mass numbers on the left-hand side = 235 + 1 = 236
Hence, 236 = 144 + 90 + 2X
So, the mass number of 2X = 236 – 144 – 90 = 2
Therefore, mass number of X = 2/2 = 1
Also, sum of atomic numbers on the left-hand side = 92 + 0 = 92
Hence, 92 = 56 + 36 + 2X
2X = 92 – 56 – 36
2X = 0
X = 0
This means X = 1 mass number, and 0 atomic number
X = neutron.
Now for the right answer to the above question:
- Option A is incorrect. electron would have 0 mass number and -1 atomic number.
- Option B is correct. neutron have these features.
- C is incorrect. neutrinos are special kind of sub-atomic particles with almost zero mass, they are seldom represented in nuclear equations.
- D is not the correct answer. A proton would have 1 mass number and 1 atomic number.
You may please note these/this:
- Neutrons are not the same as neutrinos.
- Neutrons have a notation in small letter n, with subscript as 0 and superscript as 1.
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/ culled from 2016 JAMB-UTME physics past question 14 /