Chapter 4. The Atom – Part 1. What is the atom?. Sulfur. What is the atom?. Lead. An atom is the smallest particle of an element that retains that element’s properties. From the Greek “a-tomos” which means “not divisible”.
The Atom – Part 1
Dalton's model was that the atoms were tiny, indivisible, indestructible particles and that each one had a certain mass, size, and chemical behavior that was determined by what kind of element they were.
J. J. Thomson was one of the great scientists of the 19th century; his inspired and innovative cathode ray experiment greatly contributed to our understanding of the modern world.
Thomson concluded from these two experiments, "I can see no escape from the conclusion that [cathode rays] are charges of negative electricity carried by particles of matter." But, he continued, "What are these particles? are they atoms, or molecules, or matter in a still finer state of subdivision?"
The atom as tiny, spherical and neutral body, which made up of positive and negative charged particles. These positively charged particles which later termed as proton, distributed in equally in atom and negatively charged particles (electron) embedded in these particles just like plum-pudding.