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Dalton's atomic theory was the first complete attempt to describe all matter in terms of atoms and their properties. Dalton based his theory on the law of conservation of mass and the law of constant composition. The first part of his theory states that all matter is made of atoms, which are indivisible.

Atoms have protons and neutrons in the center, making the nucleus, while the electrons orbit the nucleus. The modern atomic theory states that atoms of one element are the same, while atoms of different elements are different. ... Atoms of the same element can have different numbers of neutrons, however.

Description. Atoms are made of tiny particles called protons, neutrons and electrons. ... Stable. Most atoms are stable. ... Isotopes. Every atom is a chemical element, like hydrogen, iron or chlorine. ... Radioactive. Some atoms have too many neutrons in the nucleus, which makes them unstable. ... Ions. ... Antimatter.

Plum-pudding model (1904) Nuclear model (1911) Planetary model (1913) Quantum mechanical model (1926-present)

In chemistry and physics, the atomic theory explains how our understanding of the atom has changed over time. Atoms were once thought to be the smallest pieces of matter. However, it is now known that atoms are made up of protons, neutrons, and electrons. These subatomic particles are made up of quarks.

Ancient Greek Beliefs. Leucippus and Democritus were the first to propose, in the fifth century B.C., that all matter is made of tiny units called atoms. ... Dalton's Theory. ... J.J. ... Rutherford's Hypothesis. ... Bohr's Theory. ... Einstein, Heisenberg and Quantum Mechanics. ... Quark Theory.

Dalton's Atomic Theory (1804) All matter is composed of extremely small particles called atoms. Atoms of a given element are identical in size, mass, and other properties. Atoms of different elements differ in size, mass, and other properties. Atoms cannot be subdivided, created, or destroyed.

460 370 BC. History of the Atom - Timeline. Antoine Lavoisier. makes a substantial. ... 1766 1844. John Dalton. proposes his. ... 1743 1794. ... 1856 1940. J.J. Thomson. discovers the. ... 1871 1937. Ernest Rutherford. performs the Gold Foil. ... 1885 1962. Niels Bohr. proposes. ... 1887 1961. Erwin. Schrodinger. ... 1891 1974. James. Chadwick.

All matter is made of atoms. Atoms are indivisible and indestructible. All atoms of a given element are identical in mass and properties. Compounds are formed by a combination of two or more different kinds of atoms. A chemical reaction is a rearrangement of atoms.