Chapter 43-Models of the Atom

See representative 3D models, images, Video, animations to grasp clearly the various theories given by various scientists about Atoms (how things work, inside atoms).

They suggested what they thought would be the best explanation, BUT they had a huge constraint :- they could only infer from various experiments but could’nt physically look at atoms and molecules. Certainly they could not see inside an atom at protons, electrons, and neutrons. That’s why scientists called each theory as a ‘model’ , a construct of something they thought must be happening inside all thinsg, all substances, an “inference” based on experiments but not directly seen with their own eyes.

This is a story of scientists’ search for the smallest particles of nature.

Following topics are covered:

1) Introduction: what exactly is meant by ‘Atomic Model’ ?

2) Rutherford model

• Alpha Particle Scattering Experiment
• Idea of Nucleus as the center of an atom
• Which phenomena the model could explain
• Which phenomena the model could NOT explain

3) Hydrogen Atom and its spectrum

4) Bohr model

• Which phenomena it could NOT explain

5) Valence Shell Theory :- s,p,d and f orbitals

6) Electron Cloud model : “electrons are waves”

7) AVOGADRO Constant – Number of “Elementary Entities” in 1 mole of substance (Atoms or Molecules)

Some substances like Carbon exist as atoms in nature. Some others like Water, Oxygen, exist as molecules in nature.