2.24 Describe how the model of the atom changed from Dalton through Thompson, Rutherford, and Bohr to Schrodinger. Explain why each model changed and point out the problems with the previous model.

How did the atomic model change from Dalton to Thompson?

Dalton’s Model (1803):

Description: The atom is a solid, indivisible sphere.

Problem: This model couldn’t explain the existence of subatomic particles or chemical behavior in detail.

Thomson’s Model (1897):

Description: Known as the "plum pudding model," where the atom is a positively charged sphere with negatively charged electrons scattered within.

Change: Discovery of the electron through cathode ray experiments.

Problem: Didn’t explain how the positive charge was distributed or how electrons were held in the atom.

How did the atomic model change from Thompson to Rutherford?

Rutherford’s Model (1911):

Description: The atom consists of a small, dense, positively charged nucleus, with electrons orbiting around it.

Change: Rutherford’s gold foil experiment showed that most of the atom is empty space and that the positive charge is concentrated in the nucleus.

Problem: Couldn’t explain why electrons didn’t spiral into the nucleus due to attraction by the positive charge.

How did the atomic model change from Rutherford to Bohr?

Bohr’s Model (1913):

Description: Electrons orbit the nucleus in fixed, quantized orbits.

Change: Bohr used quantum theory to explain that electrons have specific energy levels and can only exist in these levels.

Problem: Worked for hydrogen, but failed to explain multi-electron atoms and the behavior of electrons in complex atoms.

How did the atomic model change from Bohr to Schrödinger?

Schrödinger’s Model (1926):

Description: The electron is treated as a wave, not a particle, and its position is described in terms of probability distributions (orbitals).

Change: The development of quantum mechanics and the Schrödinger equation, which accounts for the wave nature of electrons.

Problem: Solved many issues from previous models, but still cannot provide an exact location of an electron, only its probability.