John Dalton
A theory of chemical combination, first stated by John Dalton in 1803. It involves the following postulates: (1) Elements consist of indivisible small particles (atoms). (2) All atoms of the same element are identical; different elements have different types of atom.

Dalton
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.

John Dalton was an English chemist. His ideas form the atomic theory of matter.

No. Two atoms of the same chemical element are typically not identical. Since the states of the electrons in an atom are what determine the nature of the chemical bonding that the atom experiences, two atoms of the same element can react differently if they are in different states.

plum pudding model
J. J. Thomson, who discovered the electron in 1897, proposed the plum pudding model of the atom in 1904 before the discovery of the atomic nucleus in order to include the electron in the atomic model. In Thomson’s model, the atom is composed of electrons (which Thomson still called “corpuscles,” though G. J.

Thomson announced his discovery that atoms were made up of smaller components. This finding revolutionized the way scientists thought about the atom and had major ramifications for the field of physics. Though Thompson referred to them as “corpuscles,” what he found is more commonly known today as the electron.

460 BCE
According to most reports, Democritus was born circa 460 BCE and died some 90 years later, about 370 BCE.

Dalton’s Atomic Theory postulates Atoms are small, indivisible particles that make up all matter. A particular element’s atoms have the same mass, size, and other properties. Atoms of different elements can combine. Compounds are made up of atoms from various elements that combine in defined whole-number ratios.