Atomos

Description of Atomic Model

There is not an official model design, but it is represented as a a simple sphere with no internal structure, representing indivisible particles called atoms. These atoms are eternal, indestructible, and differ in shape, size, and arrangement.

Drawing and Description of Experimental Design
Democritus didn’t conduct experiments to support his theory; instead, his atomic ideas were based on philosophical reasoning and observation. He theorized that if a material were to be divided in halves, both parts would contain the same exact properties as the material as a whole.

Conclusions

He concluded that atoms are solid, indivisible and indestructible, and all matter is made up of small, atoms. These atoms can differ in shape, size, and motion, which leads to the variety of materials we see. Atoms move through empty space and combine in different ways to form everything in the universe.

Pros

It was the first atomic theory and it set a base for all other later theories. Additionally, it provided a simple concept to grasp and understand basic matter and atoms.

Cons

The theory was over simplified and left out the complexities of the atom itself, such as subatomic particles. Also, the theory did not have any experimental basis and it was purely theoretical.

Billiard Ball Model

Description of Atomic Model

Solid spheres representing atoms, envisioned as solid, indestructible units, like billiard balls. Each atom of an element being identical to others of the same element but different from atoms of other elements.

Drawing and Description of Experimental Design

Conducted experiments with gases, observing how they reacted in fixed proportions under controlled conditions. His work supported the Law of Definite Proportions, showing that chemical compounds always contain elements in the same mass proportions. He also proposed the Law of Multiple Proportions, which states that when the same elements form different compounds.

Conclusions

Atoms of the same element are identical in mass and properties, while atoms of different elements have distinct masses and properties. Dalton also explained that atoms combine in specific, whole-number ratios to form compounds and that chemical reactions involve the rearrangement of atoms . However, the atoms themselves are neither created nor destroyed, aligning with the Law of Conservation of Mass.

Pros

Based on real experiments, making it more scientific than earlier ideas. His experiments with gases provided strong evidence for his ideas. Dalton’s work became the foundation of modern chemistry, explaining how gases behave and leading to the periodic table. His theory also explained key chemical laws like the Law of Conservation of Mass, the Law of Definite Proportions, and the Law of Multiple Proportions.

Cons

Theorized that atoms were indivisible, but later discoveries showed they are made of smaller particles protons, neutrons, and electrons. He also believed atoms of the same element were identical in mass which was later disproven.

Plum Pudding Model

Description of Atomic Model

Thomson's model of the atom was completely positively charged, with small specks of electrons scattered around; it reminded him of plum pudding. It looks like a blueberry muffin, the positive charge is the bread and the blueberries are the electrons.

Drawing and Description of Experimental Design
For his experiment, Thomson vacuumed that air and placed a cathode one end of a glass tube and an anode on the other. He applied a high voltage and a light came from the cathode. He then applied an electric field that was perpendicular to the light, they ray deflected towards the positive side.
Conclusions

He came to a conclusion that cathode rays were composed of a subatomic unit called electron. He found that electrons are negatively charged and is smaller than one of the lightest elements.

Pros

He proved that atoms are divisible because there are smaller parts, founded the electron.

Cons

The model is wrong, atoms aren't completely positively charged and electrons are randomly placed.

Nuclear Model

Description of Atomic Model

Rutherford's model of the atom had a 'nucleus'; it had a center that was completely positively charged. Surrounding the nucleus were the electrons floating in empty space.

Drawing and Description of Experimental Design
For Rutherford's experiment, he aimed a stream of positive alpha particles (radiation) at a sheet of metal. His hypothesis is that if Thomson was correct then the particles would travel through the foil without any deflection. They had different deflections, some didn't deflect at all, and some did at a minor angle; But there was a part that deflected at an extreme angle.
Conclusions

He came to the conclusion that the positive charge was concentrated in one area. He thought that the part where it deflected to an extreme, was the positive center, and the part that didn't deflect at all was the negative charge. He proposed the idea that all atoms have a nucleus.

Pros

He not only proved Thomson wrong, but he also discovered another subatomic particles called protons, and presented the fact that all atoms have a nucleus.

Cons

Although he made a great discovery with protons, his model couldn't explain how electrons were arranged and the stability of the structure of an atom.

Bohr's Model

Description of Atomic Model

Bohr's model was based off of Rutherford's model, so he did have protons and a nucleus in his. But, unlike Rutherford, his model and rings around them, these rings held electrons.

Drawing and Description of Experimental Design
Both did not exactly conduct an experiment, he spent most of his time studying. Though he hypothesized that when electrons get "excited" , from an addition electrical energy, they 'jump' form one energy level to another. But, once that energy goes away or continues to die down, the electrons return to their original energy level.
Conclusions

He came to the conclusion that his hypothesis was correct, he proved that electrons can jump from each energy level then return back to its own. He also proved that electrons are just floating around next to the nucleus, but are in energy rings called orbits.

Pros

He was successful in proving that the electrons in the atoms were randomly placed, but were in energy levels call orbits.

Cons

It wasn't consistent when it came to the larger atoms, and it struggled to explain atoms with more than one electron.

Quantum Mechanical Model

Description of Atomic Model

The quantum mechanical model of an atom describes the probability of finding electrons within given orbitals. The quantum model was created when the Bohr model didn't show the wave properties of electrons. By describing electrons as waves and not particles, Schrodinger used a mathematical equation to predict the probability of finding an electron within a specific orbital in the atom.

Drawing and Description of Experimental Design
The quantum model describes the probability of the electrons in the atoms, using Schrodinger's wave equation to determine the likelihood of finding an electron at any given oribtal.

Conclusions

The quantum mechanical model of the atom takes a different view of electrons. This makes us view electrons as particles that are described by wave functions.

Pros

This model consists of mathematical equations that explain the behavior of electrons.

Cons

It was difficult to imagine this model physically.

Quantum mechanical model

Description of Atomic Model

This model consists of positively charged protons and neutral neutrons bound together to create the atom's nucleus, with negatively charged electrons occupying energy levels surrounding the nucleus. James Chadwick's atom includes the neutron placed inside of the nucleus.

Drawing and Description of Experimental Design
Chadwick had performed beryllium bombardment experiments. For his experiment, he placed polonium in a vacuum-sealed box, which radiated alpha particles through a piece of beryllium, which caused the unknown radiation to accelerate out.

Conclusions

Chadwick found out that the radiation was being composed of a mass equal to the protons, but with a neutral charge.

Pros

This helped to better understand atoms.

Cons

It didn't explain the complex behavior at the quantum level.