Step 1: Classical vs quantum mechanics.
- Newton’s laws describe motion of macroscopic objects.
- At atomic scale, particles show wave–particle duality, making Newton’s framework invalid.
Step 2: Quantum framework.
The time-dependent Schrödinger equation:
\[
i \hbar \frac{\partial \Psi}{\partial t} = \hat{H} \Psi
\]
describes how the wavefunction \(\Psi\) evolves in time.
Step 3: Conclusion.
Thus, Newton’s laws are replaced in quantum mechanics by Schrödinger’s equations.
Final Answer:
\[
\boxed{\text{Schrödinger's equations}}
\]