Democritus' model of the atom was simply a round, solid ball. Democritus knew nothing of separate protons, neutrons and electrons; all he knew was that everything physical was composed of atoms, according to Boise State ... More »

Although the early Greek philosopher Democritus hypothesized the existence of atoms, it was not until the late 1800s that English physician J.J. Thomson proposed a model for the atom. J.J. Thomson discovered the atom bec... More »

John Dalton's atomic model's name is the "billiard ball" model. This is because, according to Dalton, there are many different atoms and they cannot be broken into smaller pieces. More »

Democritus, an ancient Greek philosopher, was not the first to propose an atomic theory, as his mentor Leucippus originally proposed it. Democritus adopted the theory, developed it further, and provided a more detailed a... More »

Because ancient Greek thinkers such as Democritus lacked sophisticated technology and tools such as the microscope, his theory of the atom was due more to thought experimentation than to hard empirical observation, as us... More »

The term "atomic radius" refers to the measured distance between the nucleus of an atom and the furthest orbiting electron. The outermost electron is referred to as a valance electron. The effective nuclear charge of an ... More »

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Atomic mass is the mass of a single atom or an individual isotope. The atomic weight is the average mass of all naturally occurring isotopes of an element. More »