Hypothesis according to Aristotle (350 BC): All matter consists of the elements earth, air, fire, and water.
Experiment: A tree grows from the earth as water is added. The tree is then set on fire in an effort to form new elements.
1. What kind of results would be observed from this experiment? Fire, ash (earth), smoke (air)
2. Would these observations support or reject the hypothesis? Explain. Support. No elements have been produced that are something other than the four elements from the hypothesis.
New information: Hooking up two wires to opposite electrodes of a battery and submerging the free ends of the wires into water causes bubbles to form on each wire. The wire hooked up to the negative electrode always produces exactly twice the volume but only 1/8 of the mass as the gas from the positive electrode.
3. How does this new information support the original hypothesis? Air is formed from the water.
4. How does this new information contradict the original hypothesis? Clearly, we have two different types of air. The smaller volume of air is much heavier than the larger volume of air. Air cannot be a single element.
New hypothesis according to Dalton (1803): All matter is composed of tiny, indivisible, electrically neutral spheres called atoms. Atoms of the same element are all identical. Atoms of different elements have different masses.
Experiment: Neutral atoms sealed in a cathode ray tube produce a beam of particles that are attracted to the positive end of a magnet, but repelled by the negative end.
5. How does this experiment contradict Dalton's hypothesis? Dalton said that atoms are indivisible, meaning they are the smallest particle in existence. The negatively charged beam of particles could only have come from the neutral atoms meaning that there must be particles smaller than the atom itself.
Experiment: A sample of neon gas is passed through a mass spectrometer. The spectrometer records that 82% of the atoms in the sample have a mass of 20 u. The other 18% have a mass of 18 u.
6. What do we call atoms of the same element that have different masses? Isotopes.
7. How does this experiment contradict Dalton's hypothesis? Atoms of the same element are not always identical.
8. Propose a new hypothesis for the structure of an atom. Hint: How can an atom be neutrally charged and contain charged particles at the same time? The atom must be made up of both positively charged and negatively charged particles. Your hypothesis should describe how those particles might be arranged.
9. Compare your model to that of J.J. Thomson (p.110) proposed in 1897. Thomson proposed that the electrons were like chocolate chips embedded in a positively charged ball of cookie dough.
New information: Tiny positively charged alpha particles shot at close to the speed of light at a thin sheet of gold foil passed straight through without being deflected about 99.99% of the time. About 1 in every 20,000 alpha particles was repelled straight back. The only way this could happen is if the alpha particle encountered a very large positive charge in an extremely small region of the atom.
10. Revise your hypothesis from #8 as needed. All of the positively charged particles must be crammed into a really tiny nucleus.
Hypothesis according to Rutherford (1911): An atom consists of a very dense, positively charged nucleus with the electrons roaming through the rest of the atom, which is mostly empty space.
New information: Neils Bohr viewed the bright-line spectra produced by gaseous atoms that were energized. He reasoned that the lines represented specific "jumps" by the excited electrons.
11. How does this information contradict Rutherford's hypothesis? Electrons cannot roam at random. They must have a definite structure (rings).
Hypothesis according to Bohr (1913): The nucleus contains protons and neutrons while the electrons orbit the nucleus in distinct rings. The rings are like rungs on a ladder. The electrons can jump from one ring to another, but can never stay in between adjacent rings.
New information: X-ray diffraction allows us to determine the 3-D shaped of molecules. We know the bonds form when electrons are shared among different atoms. The ring structure described by Bohr cannot account for the shapes of molecules.
New hypothesis (current): Electrons reside in orbitals of a specific shape (electron clouds). These orbitals and their orientations determine the 3-D shape of a molecule.
12. Why do you suppose Aristotle's hypothesis lasted for thousands of years while the more accurate hypotheses have lasted for much shorter periods? We did not have the technology to examine extremely small particles back in 400 B.C.
As technology continues to advance, our ability to peer inside the world of atoms also becomes more advanced.
You May Also Find These Documents Helpful
-
A new atomic theory, in which all atoms of the same element are identical to one another and equal in mass, was proposed by the scientist Dalton. Although the theory had its flaws and was simple, it was revolutionary. Scientists became able to study the actual structure and mass of atoms after the discovery of radioactivity. Soon, isotopes were discovered, as atoms of the same element which have been built up to have different masses.…
- 1323 Words
- 6 Pages
Powerful Essays -
A new atomic theory, in which all atoms of the same element are identical to one another and equal in mass, was proposed by the scientist Dalton. Although the theory had its flaws and was simple, it was revolutionary. Scientists became able to study the actual structure and mass of atoms after the discovery of radioactivity. Soon, isotopes were discovered, as atoms of the same element which have been built up to have different masses.…
- 1188 Words
- 5 Pages
Good Essays -
Democritus was the first man to suggest the existence of atoms and in suggesting their existence he also defined their possible characteristics. “He reasoned that if the stone were to be continually cut into smaller…
- 813 Words
- 4 Pages
Good Essays -
I gathered my materials from the material list and set up my data table. I combined the zinc and HCl, then captured the Hydrogen that was produced and observed the combustion reaction with a flame. I then captured more hydrogen to use later in the experiment. I combined manganese with hydrogen peroxide which bubbled much the same as the zinc and HCl to produce oxygen. I observed the reaction of the oxygen with a burning ember. I then captured more oxygen in the bulb with the hydrogen, and observed itʼs reaction of extinguishing the flame. I then produced carbon dioxide in a few different ways. Put lime water in a well, mixed baking soda and vinegar, and observed the limewater turning murky and grey, an indication of CO2. Then did the same with a well of bromothymol blue which indicated an acid. I exposed this gas to a flame and the flame extinguished immediately. I then combined alka-seltzer and water, and inserted the gas into the lime water again. I then tested the CO2 from my breath with the lime water.…
- 784 Words
- 4 Pages
Good Essays -
f. Light a match, and while holding the hydrogen pipet bulb horizontal and about 1cm from the flame, gently squeeze a small amount of gas towards the flame and watch the reaction.…
- 1568 Words
- 7 Pages
Powerful Essays -
Both John Dalton and Ernest Rutherford, among other great researchers and scientists, assisted in creating the atomic theory that exists today. Dalton's theory was the first modern atomic theory, but a part of it was disproven by Rutherford. Rutherford found atoms were not indivisible and that they consist of smaller parts and particles. Even though one of Dalton's ideas was proved wrong, his other thoughts still apply to today's atomic…
- 272 Words
- 2 Pages
Good Essays -
1. Explain how scientific observations led to the development of, and changes to, the periodic table.…
- 2160 Words
- 7 Pages
Good Essays -
In 1908 Rutherford demonstrated and made an airtight glass tube with very thin walls, and filled it with the radioactive radium emanation. Alpha particles could penetrate the thin walls of the tube and were collected in a second tube. Rutherford was then inspired to investigate more into Alpha Particles.…
- 1488 Words
- 6 Pages
Good Essays -
Democritus was the first scientist to create a model of the atom as well as the first to discover that all matter is made up of indivisible particles called atoms. His belief in atoms was that atoms were small, hard particles that were all made of the same material but were different shapes and sizes. Furthermore he believed that atoms were infinite in shape, in number, always moving and capable if joining together. Unlike Democritus's belief, Aristotle's belief about the atom were completely different. For instance, he disagreed with Democritus's belief and instead believed that there was no smallest part of matter and that different substances were made of earth, fire, air, and water.…
- 859 Words
- 4 Pages
Good Essays -
John Dalton is a chemist who was born on September 6, 1766, in Eaglesfield, England. In 1803 John Dalton created the Dalton’s Atomic Theory. When Dalton’s atomic theory was created chemists believe his ideas were untrue. Even though Dalton’s atomic theory is two centuries old scientist still question to this day whether his theory has been proven correctly or incorrectly. There appear to be many articles out there pointing out what was inaccurate about his theory. However, still to this day chemist/people believe some of his theories are correct. Dalton’s hypothesis tried to prove the matter in the terms of atoms and properties. I discovered two articles that I referred to the first article is called the “Atomic Theory of Matter” This article was last updated on July 20, 2016. The second article I discovered is called “Postulates of Dalton’s Atomic Theory”. This article was last updated on March 21, 2017. The articles describe what is true and false about Dalton’s theory. According to Dalton's atomic theory, it was stated Dalton atomic theory was the first work created that describes the atoms and properties. Dalton discusses four theories. The first part of his theory reads all matter is formed of atoms which are unable to break down. The second part of his theory reads atoms are similar in mass and properties. The third part of his theory reads combinations of two or more different types of…
- 462 Words
- 2 Pages
Good Essays -
Of all of the many scientists who played a major role in the formation of the atomic theory, it is believed that Dalton, Rutherford, Thompson, Bohr, and Planck are the five most influential. The research of this theory has gone on for many years and each and every one of them have brought us closer to our current understanding of the atom today. Each one of them played a special role in the development process of the atom and most importantly, they all reflected on one another. Many influential scientists follow up on one another proving their own theories correct and in time, create challenges for the next scientist to question. This truly, is one of the main reasons we have gotten so far with the atom. These amazing discoveries mostly started…
- 1691 Words
- 7 Pages
Better Essays -
The scientist we chose for our project is John Dalton. Who is John Dalton, you might ask? John Dalton was an English chemist, physicist, and meteorologist. He is best known for the discovery of the modern atomic theory. The rules for the atomic theory are that all matter is made up of tiny particles, or atoms, atoms are always invisible and indestructible, all atoms of a given element are identical in mass and properties, compounds are formed by a combination of two or more different kinds of atoms, and a chemical reaction is a rearrangement of atoms.…
- 1617 Words
- 7 Pages
Better Essays -
These cathode-ray particles are now known as electrons. Soon after the discovery of electrons the proton was discovered. This led Thomson to conclude that ther were an equal number of both particles present in the atom. Twelve years later Lord Ernest Rutherford was experimenting with alpha particles. He shot a stream of them at a piece of gold foil surrounded by zinc-sulfide.…
- 638 Words
- 3 Pages
Good Essays -
Have you ever wondered how the atomic theory came to be? Or have you have wondered who it was that helped in its development? There was not just one man who came up with the atomic theory, but there were many scientists that contributed to its development. One of these scientists was Democritus, a Greek philosopher. Democritus was the son of Hegesistratus, and he was a student of Magians and Chaldaeans. By some authorities he was thought of as the greatest of the Greek physical philosophers. He was born in Abdera in Thrace sometime between 470 and 460 BC. Democritus studied under the Greek philosopher Leucippus, whose system he later on developed further. Democritus visualized atoms; atom is a Greek word for indivisible, which means as moving through space, then colliding to form the universe and the natural objects in it. Democritus was said to have excelled in all the branches of knowledge. “His name was associated with the first exposition of the atomic theory of matter, according to which all matter is composed of single, indivisible atoms exactly alike qualitatively.” (Greek: pg 1)…
- 1801 Words
- 8 Pages
Good Essays -
However, not everyone agreed with his knowledge. Plato and Aristotle, who were philosophical leaders at the time, disagreed with Democritus because they believed there was no explanation or evidence for holding atoms together. They also thought that it countered the ideas of fundamental elemental substances. During the mid to late 1700’s, Antoine Lavoisier had the first discussion about the Law of Conservation of Mass or Matter which stated that matter cannot be created nor destroyed through chemical reaction. This continues to be a law that is followed even today. In the late 1700’s Joseph Proust proved that pure compounds would always be made up of the same elements, and these elements would be proportioned by mass. The Law of Constant Composition stated that pure compounds are always made up of the same elements in the same proportion by mass. John Dalton used this information from those before him to create the Atomic Theory in the early 1800’s. This theory stated that all elements are made up of tiny particles called atoms – taken from Democritus’ idea of “atomos”. These atoms were identical in the same element and could not be created nor destroyed in a chemical reaction. The last part of the Atomic Theory stated that atoms of different elements combine in simple whole number ratios to form pure…
- 700 Words
- 3 Pages
Good Essays