Poetry of Physics and the Physics of Poetry

The Structure of the Atom 161

Soon after Thomson’s discovery of the electron, two models of the
atom arose. According to the proponents of one point of view, the atom
was a miniature solar system. There was a positively charged nucleus
at the centre of the atom around which orbited the negatively charged
electrons, as pictured in Fig. 17.1. This model, which eventually
developed into our present-day notion of the atom, was in fierce
competition with a model proposed by Thomson himself, which he
called “the plum pudding model” of the atom. He assumed that the atom
was a sphere of positive charge in which the electrons were embedded
like plums in a pudding as pictured in Fig. 17.2. In both models, the atom
was basically neutral. The atom became a positive or negative ion as
electrons were either lost or gained. Both models explained the results of
the electrolysis and gas discharge experiments.

154 The Poetry of Physics and The Physics of Poetry

Soon after Thomson's discovery of the electron, two models of the

atom arose. According to the proponents of one point of view, the atom

was a miniature solar system. There was a positively charged nucleus at

the centre of the atom around which orbited the negatively charged

electrons, as pictured in Fig. 17.1. This model, which eventually

developed into our present-day notion of the atom, was in fierce

competition with a model proposed by Thomson himself, which he

called "the plum pudding model" of the atom. He assumed that the atom

was a sphere of positive charge in which the electrons were embedded

like plums in a pudding as pictured in Fig. 17.2. In both models, the atom

was basically neutral. The atom became a positive or negative ion as

electrons were either lost or gained. Both models explained the results of

the electrolysis and gas discharge experiments.

Fig. 17.1 Fig. 17.2

The plum pudding atom, however, gained favour over the miniature solar

system atom because it provided a more satisfactory description of the

electromagnetic radiation emitted by matter. The light emitted by various

materials was examined by passing it through a prism before it fell upon

a photographic plate. This enabled the experimentalists to determine the

spectral distribution of the light being radiated by a particular material.

They found that the spectra from the closely-packed solids and liquids

are continuous, but, that the spectra from the gases are distinguished by

discreet lines. Apparently, the continuous spectra were due to the

external motion of the atom as a whole, due to heat. This was verified by

the fact that the distribution of frequencies changed with the temperature,

so that the higher the temperature the higher the frequency of the

radiation. This is to be expected since the frequency of the light emitted,

according to Maxwell's theory of radiation, is related to the frequency of

the charged particles emitting the radiation. As the solid or liquid is

heated, the atoms move faster and, hence, one expects a shift to higher

Fig. 17.1

154 The Poetry of Physics and The Physics of Poetry

Soon after Thomson's discovery of the electron, two models of the

atom arose. According to the proponents of one point of view, the atom

was a miniature solar system. There was a positively charged nucleus at

the centre of the atom around which orbited the negatively charged

electrons, as pictured in Fig. 17.1. This model, which eventually

developed into our present-day notion of the atom, was in fierce

competition with a model proposed by Thomson himself, which he

called "the plum pudding model" of the atom. He assumed that the atom

was a sphere of positive charge in which the electrons were embedded

like plums in a pudding as pictured in Fig. 17.2. In both models, the atom

was basically neutral. The atom became a positive or negative ion as

electrons were either lost or gained. Both models explained the results of

the electrolysis and gas discharge experiments.

Fig. 17.1 Fig. 17.2

The plum pudding atom, however, gained favour over the miniature solar

system atom because it provided a more satisfactory description of the

electromagnetic radiation emitted by matter. The light emitted by various

materials was examined by passing it through a prism before it fell upon

a photographic plate. This enabled the experimentalists to determine the

spectral distribution of the light being radiated by a particular material.

They found that the spectra from the closely-packed solids and liquids

are continuous, but, that the spectra from the gases are distinguished by

discreet lines. Apparently, the continuous spectra were due to the

external motion of the atom as a whole, due to heat. This was verified by

the fact that the distribution of frequencies changed with the temperature,

so that the higher the temperature the higher the frequency of the

radiation. This is to be expected since the frequency of the light emitted,

according to Maxwell's theory of radiation, is related to the frequency of

the charged particles emitting the radiation. As the solid or liquid is

heated, the atoms move faster and, hence, one expects a shift to higher

Fig. 17.2

The plum pudding atom, however, gained favour over the miniature
solar system atom because it provided a more satisfactory description of
the electromagnetic radiation emitted by matter. The light emitted by
various materials was examined by passing it through a prism before it
fell upon a photographic plate. This enabled the experimentalists to
determine the spectral distribution of the light being radiated by a
particular material. They found that the spectra from the closely-packed
solids and liquids are continuous, but, that the spectra from the gases are
distinguished by discreet lines. Apparently, the continuous spectra were
due to the external motion of the atom as a whole, due to heat. This was
verified by the fact that the distribution of frequencies changed with the
temperature, so that the higher the temperature the higher the frequency
of the radiation. This is to be expected since the frequency of the light
emitted, according to Maxwell’s theory of radiation, is related to the
frequency of the charged particles emitting the radiation. As the solid or