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Date of Discovery/Contribution:
430 BCE

Description/explanation of their contribution/model:
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Democritus described atoms as indivisible, small, uniform, and hard. He named it “Atomos”. There were many atoms discovered and they were formed in different shapes and sizes. He also believed that atoms have collided in an empty space causing them to repel or to connect.
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🔘

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Date of Discovery/Contribution:
1800

Name of Atomic Model:
Solid Sphere Model

Description/explanation of their contribution/model:
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Dalton had 4 parts in his theory. First, he believed that all matter is made up of atoms in which the particles are indivisible. Second, all of the given elements are the same in mass and properties. Third, compounds are composed of two or more atoms. Lastly, a chemical reaction is a rearrangement of atoms.
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🔵

# data[].attributes.body
Date of Discovery/Contribution:
1897

Name of Atomic Model:
Plum Pudding Model

Description/explanation of their contribution/model:
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J.J. Thomson first had an experiment named “the Cathode Ray Experiment”. He applied a high electric voltage at the end of the tube between the electrodes. A beam of particles was shown and it can be visible by passing through first at the cathode (negatively charged electrode) to the anode (positively charged electrode), this beam of particles was named cathode ray. The phosphor should be at the far end of the tube and it is responsible for detecting the ray. To start the experiment, he placed the negative and positive charged plates around the cathode ray. The experiment showed that the cathode ray was passing towards the positively charged plates and the negatively charged plate was blocked. At this experiment, he discovered that the ray is composed of negatively charged particles. He believed then that the atom has a positively charged model and inside were the negatively charged electrons scattered around it just like a plum pudding.
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🟤

# data[].attributes.body
Date of Discovery/Contribution:
1908

Name of Atomic Model:
Nuclear Model

Description/explanation of their contribution/model:
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Rutherford performed an experiment called “the Gold Foil Experiment”. In this experiment, he used alpha particles and fired a thin sheet of gold composed of tiny positively-charged particles. He examined that most of the alpha particles passed through and absorbed the gold foil, some were  slightly deflected, and others bounced back. After the experiment, Rutherford concluded that an atom must have an empty space since most of the alpha particles passed through the gold foil. In his nuclear model, protons and neutrons are believed to be at the center of an atom and in the nucleus, and electrons are found outside the nucleus occupying the empty space.
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🟢

# data[].attributes.body
Date of Discovery/Contribution:
1913

Name of Atomic Model:
Planetary Model

Description/explanation of their contribution/model:
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Bohr’s planetary model was an adaptation of Rutherford’s model. What makes Bohr’s model different is that he used quantum mechanics to determine the energy level of an electron. The atomic model is composed of electrons orbiting around the nucleus. The energy of the orbit is related to its size meaning the lowest energy is supposedly at the smallest orbit. He believed that his model is similar to planets orbiting the sun.
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⚫

# data[].attributes.body
Date of Discovery/Contribution:
1926

Name of Atomic Model:
Quantum Mechanical Model

Description/explanation of their contribution/model:
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Schrodinger used mathematical equations to solve the position of an electron. Unlike in Bohr’s model, finding the exact path of electrons is based on orbits around the nucleus. The only solution to find the possible answers for Schrodinger’s theory is called “Wave Functions”. Wave functions can only give you the probability of finding an electron around the nucleus.
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🟣

# data[].attributes.body
Date of Discovery/Contribution:
1932

Description/explanation of their contribution/model:
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Chadwick discovered more about the subatomic particle neutron. He, later on, measured the mass of the neutron;

He observed that neutrons are neutrally-charged and have the same mass as the protons.
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🟡