2. SOLID SPHERE MODEL
The Solid Sphere Model was the first atomic model and was developed by
John Dalton in the early 19th century. He hypothesized that an
atom is a solid sphere that could not be divided into smaller particles.
He came up with his theory as a result of his research into gases.
He realized that certain gases only combined in specific proportions.
He recognized atoms of a particular element differ than the other element.
3. PLUM PUDDING MODEL
The plum pudding model is one of several historical scientific models of
the atom. First proposed by J. J. Thomson in 1904 soon after the discovery
of the electron, but before the discovery of the atomic nucleus, the model
tried to explain two properties of atoms then known: that electrons are
negatively charged particles and that atoms have no net electric charge. The
plum pudding model has electrons surrounded by a volume of positive
charge, like negatively charged "plums" embedded in a positively charged
"pudding".
4. NUCLEAR MODEL
Rutherford's atomic model became known as
the nuclear model. In the nuclear atom, the
protons and neutrons, which comprise nearly
all of the mass of the atom, are located in the
nucleus at the center of the atom. The electrons
are distributed around the nucleus and occupy
most of the volume of the atom.
5. PLANETARY MODEL
Following the discoveries of hydrogen emission spectra and the
photoelectric effect, the Danish physicist Niels Bohr
(1885-1962) proposed a new model of the atom in 1915.
Bohr proposed that electrons do not radiate energy as they orbit the
nucleus,
but exist in states of constant energy that he called stationary states.
This means that the electrons orbit at fixed distances from the nucleus
(see below).
Bohr's work was primarily based on the emission spectra of hydrogen.
This is also referred to as the planetary model of the atom.
It explained the inner workings of the hydrogen atom.
Bohr was awarded the Nobel Prize in physics in 1922 for his work.
6. QUANTUM MODEL
A powerful model of the atom was developed by Erwin Schrödinger
in 1926. Schrödinger combined the equations for the
behavior of waves with the de Broglie equation
to generate a mathematical model for the distribution of electrons in
an atom.
