Answer:
B) 85
Explanation:
In the nuclear fission of uranium-235, a nucleus of uranium-235 absorbs a slow-moving neutron and then decays into a nucleus of Kripton-92, a nucleus of Barium-141 (which is the missing nucleus in the figure) and three more neutrons.
Knowing that:
- Uranium has atomic number 92, so it has 92 protons
- Kripton has atomic number 36, so it has 36 protons
- Barium has atomic number 56, so it has 56 protons
We can calculate the number of neutrons in the nucleus of barium, since we know that the total number of neutrons must be conserved. We have:
- On the left side of the reaction: (235-92) neutrons of the uranium + 1 neutron absorbed = 144 neutrons
- On the right side of the reaction: (92-36) neutrons of the krypton + X neutrons of the barium + 3 neutrons = 144
So we get:
56 + X + 3 = 144
X = 85
So, the nucleus of barium has 85 neutrons.
