The Evolution of the Atom

His Theory and Contribution

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Democritus believed that atoms were uniform, solid, hard, incompressible, and indestructible and that they moved in infinite numbers through empty space until stopped. Differences in atomic shape and size determined the various properties of matter.

His Exepriment

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Democritus had a thought experiment. The idea was if you took a material and divided it half, you would have a smaller but identical chunk. If you keep dividing your material, there should eventually be a point where you've reached the smallest representative element of your material. That element is the"atom".

His Model

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His work with the Atomic Theory

Antoine Lavoisier's work in defining the law of conservation of mass would help to shape atomic theory. This discovery was influential in atomic theory because it defined that matter was composed of atoms that were not created or destroyed during chemical reactions

What Experiment Did He Do?

His experiment is when he reacted oxygen with inflammable air, obitiang “water in a very pure state” He proved that water was not an element but a compound of oxygen and inflammable air, or hydrogen. To support his hypothesis he decomposed water into oxygen and inflammable air..

Atoine's Model

His Theory

Dalton proposed that every single atom of an element, such as gold, is the same as every other atom of that element. He also noted that the atoms of one element differ from the atoms of all other elements. Today, we still know this to be mostly true.

His Expiriment

In 1803 Dalton discovered that oxygen combined with either one or two volumes of nitric oxide in closed vessels over water and this pioneering observation of integral multiple proportions provided important experimental evidence for his incipient atomic ideas.

Dalton's Model

His Atomic Theory

Thomson’s experiment would use cathode ray tubes which showed that all atoms contain tiny negatively charged subatomic particles or electrons. He is most known for his proposed the plum pudding model of the atom, which had negatively-charged electrons embedded within a positively-charged "soup."

J.J.'s Model

His Contribution

Planck called the packets of energy quanta and he was able to determine that the energy of each quantum is equal to the frequency of the radiation multiplied by a universal constant that he derived, now known as Planck's constant

His Theory

Planck decided to study black body radiation in more detail and found something very interesting. Black bodies always radiated an amount of energy that was proportional to the frequency of the electromagnetic waves they absorbed. He was surprised to find that energy was always emitted in tiny, discrete packets.

Max's Model / Theory

Marie's Contribution to the Atom

She deduced that radioactivity does not depend on how atoms are arranged into molecules, but rather that it originates within the atoms themselves.

Marie tested all the known elements in order to determine if other elements or minerals would make air conduct electricity better, or if uranium alone could do this.

Marie's Theory

His Theory

In 1910 Robert Millikan succeeded in precisely determining the magnitude of the electron's charge. Small electrically charged drops of oil were suspended between two metal plates where they were subjected to the downward force of gravity and the upward attraction of an electrical field.

His Contribution

His contribution to the atomic theory was that In 1910, Robert Millikan discovered the charge of an individual electron. He published his results in 1913. Millikan also made the discovery that all electrons carry the same amount of negative charge.

Robert's Expeirment

His Theory

His model escribed the atom as a tiny, dense, positively charged core called a nucleus, in which nearly all the mass is concentrated, around which the light, negative constituents, called electrons, circulate at some distance, much like planets revolving around the Sun. This proposed that the negatively charged electrons surround the cules of the atom, he also claimed that the electrons surrounding the nucleus revolve around it in an orbit like pattern, calling these orbits.

Ernest's Model

Albert's Contribution and Theory

Einstein also in 1905 mathematically proved the existence of atoms, and thus helped revolutionize all the sciences through the use of statistics and probability. Atomic theory says that any liquid is made up of molecules (invisible in 1905). Furthermore, these molecules are always in random, ceaseless motion

Einstein explained the photoelectric effect. He showed that when quanta of light energy strikes atoms in the metal, the quanta force the atoms to release electrons.

Albert Einstein theory helped revolutionize all the sciences through the use of statistics and probability

The Equation

E=MC^2

His Theory and Contribution

He proposed that the electrons travel around the nucleus of an atom in distinct circular orbits, or shells. The model is also referred to as the planetary model of an atom.

Niels Bohr contribution was the proposals of a theory for the hydrogen atom, based on quantum theory that some physical quantities only take discrete values. Electrons move around a nucleus, but only in prescribed orbits, and If electrons jump to a lower-energy orbit, the difference is sent out as radiation.

His Experiment

Bohr did The Franck-‐Hertz experiment provided support for the Bohr model of the atom. In the Franck-‐Hertz experiment, electrons were accelerated through a low-‐pressure gas. Collisions of the electrons with the gas atoms could provide enough energy for the electrons in the gas atoms to move from one energy level to another.

Neil's Model

His Contribution and Theory of the Atom

The Schrödinger model assumes that the electron is a wave and tries to describe the regions in space, or orbitals, where electrons are most likely to be found.

His Experiment and Equation

Erwin Schrödinger's most famous thought experiment became known as “Schrödinger's cat”: A cat is in a box with a vial of poison. The vial breaks if an atom inside the box decays. The atom is superposed in decay and non-decay states until it is observed, and thus the cat is superposed in alive and dead states

In 1926 Erwin Schrödinger formulated a wave equation that accurately calculated the energy levels of electrons in atoms.

His Model

James' Model

James' Theory and Contribution

The atomic model after Chadwick's discovery consisted of what can be seen below; positively charged protons and neutral neutrons bound together as the atom's nucleus, with negatively charged electrons occupying energy levels surrounding the nucleus.

The atomic model after Chadwick's discovery consisted of positively charged protons and neutral neutrons bound together as the atom's nucleus, with negatively charged electrons occupying energy levels surrounding the nucleus.

Louis' Contribution and Theory

In 1924 Louis de Broglie introduced the idea that particles, such as electrons, could be described not only as particles but also as waves. This was substantiated by the way streams of electrons were reflected against crystals and spread through thin metal foils.

Louis' Model

His Theory on the Atom

Heisenberg developed a mathematical way of expressing the energy levels of electrons in atoms. His theory states that there is uncertainty in measuring such features of a particle as the position and momentum of an electron are hard to predict.

His Experiment

Heisenberg conducted a thought experiment as well. He considered trying to measure the position of an electron with a gamma ray microscope. The high-energy photon used to illuminate the electron would give it a kick, changing its momentum in an uncertain way.

His Model