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440
The beginning of Atomic Theory
440 BCE, A Greek philosopher named Democritus thought that there would be something called particle which would be impossible to be broken down. The particle was called atom which is from a Greek word atomos, meaning "not able to be divided". He also thought that atoms were made of a single material formed into different shapes and sizes. -
Dalton's Atomic Theory
A British chemist and schoolteacher, John Dalton experimented with different substances and his results suggested that elements combine in certain proportions because they are made of single atoms. He also published his atomic theory in 1803. He also made a model of atom called the solid ball. -
Thomson's Discovery of Electrons
A British Scientist named J.J Thomson discovered that there are small particles inside an atom and also that they can also be divided into smaller parts. Thomson experimented with a cathode-ray tube and discovered that the positively charged plate attracted to the beam and he also concluded that the beam was made of negative electric charges and they are called electrons. -
Thomson's model
After learning about the atoms, he proposed a new model of the atom called the Plum Pudding. It was named after a desert that was popular in Thomson's day. -
Rutherford's Atomic Experiment
Thomson's student named Ernest Rutherford designed an experiment to study the parts of atom. His experiment was called The Gold Foil Experiment. He expected that the light would cross the gold in a straight line. But his great surprise was that some of particles were deflected and some bounced straight back. -
Far from the Nucleus
Rutherford revised the atomic theory again and made a new model of the atom. He proposed that in the center of the atom there is a tiny, extremely dense and small, positively charged part called nucleus. -
Bohr's Electron Levels
A Danish scientist who worked with Rutherford, studied the way that atoms react to light. He proposed that electrons move around the nucleus in certain paths, or energy levels. Electrons can jump from a path in one level to another level. He also made a model called the planetary model explaining about the way atoms react to light. -
The Modern Atomic Theory
An Austrian physicist named Erwin Schrodinger and a German physicist named Werner Heisenberg further explained the nature of electrons. According to the current theory there are reigns inside the atom where electrons are likely to be found and these reigns are called electron clouds. Erwin Schrodinger also a model called the Electron cloud model which explains all about electrons surrounded the nucleus in electron cloud.