10217 Hyeonseung Song
International Course 1-2
In 1803, John Dalton proposed his atomic model, which described the atom as a very small, solid particles, which could not be further divided into smaller parts.
The main points of Dalton 's atomic theory were:
Matter consists of extremely small particles called atoms, and these atoms are indivisible and indestructible.
All atoms of a given element are identical(size, mass, and many other properties,) but atoms of different elements are different from one another.
Atoms of different elements combine in simple whole-number ratios to form chemical compounds. A compound has the same relative numbers and types of atoms.
In chemical reactions, atoms are reorganized, and the way in which they are bound together change. The atoms themselves remain unchanged.
Among these four main points, two proved to be incorrect.
Contrary to what the first main point of Dalton’s atomic theory asserted, atoms are not indivisible; atoms are made up of neutrons, protons, and electrons, and therefore, an atom can be divided into smaller particles.
Unlike the second main point of Dalton’s atomic theory, not all atoms of the same element are identical in their properties, since there are different variants for a given element, which differ in neutron number, and furthermore weight -- these variants are called the isotopes of the element.
Dalton’s atomic model was followed by Thomson’s atomic model,