Explain the concept of 'electron cloud' in the modern atomic model, contrasting it with Bohr's fixed orbits.

In the modern atomic model (quantum mechanical model), the 'electron cloud' represents the region around the nucleus where an electron is most likely to be found. It's a probabilistic model, meaning we cannot pinpoint an electron's exact location but can describe its probable distribution. This contrasts with Bohr's model, which depicted electrons orbiting the nucleus in fixed, well-defined circular paths or orbits.