1. Discuss problems of building models of atoms
The main problem with Bohr's model is that it works very well for atoms with only one electron, like H or He+, but not at all for multi-electron atoms. Bohr was able to predict the difference in energy between each energy level, allowing us to predict the energies of each line in the emission spectrum of hydrogen, and understand why electron energies are quantized.
Bohr's model breaks down when applied to multi-electron atoms. It does not account for sublevels (s,p,d,f), orbitals or elecrtron spin. Bohr's model allows classical behavior of an electron (orbiting the nucleus at discrete distances from the nucleus.
The application of Schrodinger's equation to atoms is able to explain the nature of electrons in atoms more accurately.
The main problem with Rutherford's model was that he couldn't explain why negatively charged electrons remain in orbit when they should instantly fall into the positively charged nucleus.
The problems with dalton's model were:
The indivisibility of an atom was proved wrong: an atom can be further subdivided into protons, neutrons and electrons. However an atom is the smallest particle that takes part in chemical reactions.
According to Dalton, the atoms of same element are similar in all respects. However, atoms of some elements vary in their masses and densities. These atoms of different masses are called isotopes. For example, chlorine has two isotopes with mass numbers 35 and 37.
Dalton also claimed that atoms of different elements are different in all respects. This has been proven wrong in certain cases: argon and calcium atoms each have an atomic mass of 40 amu. These atoms are known as isobars.
According to Dalton, atoms of different elements combine in simple whole number ratios to form compounds. This is not observed in complex organic compounds like sugar (C12H22O11).
The theory fails to explain the existence of allotropes; it does not account for differences in properties of charcoal, graphite, diamond.
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