Can someone explain the evolving of the atom?

Question

like dalton's theory and Bohrs theory and stuff like that

Answer 1

Atoms haven't evolved but our understanding of them has :)

Atom, from the Greek "indivisible," was a philosophical notion that there was a smallest unit of a material. In Western thought, this idea arose in about 450 BCE in ancient Greece. The notion of both atoms and how they combined to form more complex compounds arose about a century earlier in India.

It was not until 1803 that Dalton took atoms from the philosophical into the scientific with his experiments in chemical proportions. He proposed that each element was composed of atoms and that atoms combined in various proportions to form compounds.

The size of atoms was investigated through experimenters ranging from Benjamin Franklin (who used oil films on water to establish an upper bound on the size of the smallest particles of oil) to Robert Brown, who observed the erratic motion of dust particles in fluid under a microscope. Albert Einstein later attributed this "Brownian Motion" to collisions with individual water molecules.

Upon the discovery of "cathode rays" efforts were made to describe the structure of the atom. An early effort by J.J. Thompson described the atom as a "plum pudding" with charged but nearly massless electrons embedded in a heavy positive fluid. The scattering experiments of Ernest Rutherford and his students Geiger (of Geiger counter fame) and Marsden established the "nuclear model" of the atom, in which all of the positive charge and virtually all of the mass were confined to a tiny nucleus. Further theory and experiments led to the "Bohr Model" of the atom, which is almost entirely incorrect but explains some aspects of the atom so well that it is still taught today in introductory-level science classes.

The modern model of the atom is one in which the electrons are described by their quantum-mechanical wave functions.