Final answer:
The missing particle in the nuclear equation is 140Ba.
Step-by-step explanation:
The missing particle in the nuclear equation is 140Ba.
In the equation 235U → 90Sr + ? + 210n + 400γ, the missing particle is the product of the nuclear reaction. In this case, the product is 140Ba, which is represented by the symbol Ba and the mass number 140.
When balancing a nuclear equation, it is important to ensure that both the total number of protons and the total number of mass units are conserved on both sides of the equation. Balancing nuclear equations is crucial not only for conserving the total number of protons and mass units but also for maintaining the overall integrity of the nuclear reaction, ensuring it adheres to the principles of conservation of energy and mass.