1. Erwin Schrödinger
The many problems with the Bohr model were corrected by Erwin Schrödinger, an Austrian physicist.
The Schrödinger Equation:

2. Erwin Schrödinger
Schrödinger introduced the wave function, a function of position and time whose absolute value squared is related to the probability of finding an electron near a specific point in space and time.

3. Erwin Schrödinger
In this theory, the electron can be thought of as being spread out over a large volume and there are places where it is more likely to be found than others! This can be thought of as an electron cloud.

4. Heisenberg Uncertainty Principle
It is not possible to measure simultaneously the position AND momentum of a particle with absolute precision.
ΔxΔp ≥ h/4π
Also ΔEΔt ≥ h/4π