Atomic Theory

1.)Who were the main characters in the development of the atom?

• Democritus- Stated that all matter is composed of atoms, of small indestructible particles. The atoms themselves remain unchanged, but move about in space to combine in various ways to form all macroscopic objects. Early atomic theory stated that the characteristics of an object are determined by the shape of its atoms. So, for example, sweet things are made of smooth atoms, bitter things are made of sharp atoms.
• John Dalton-Along with the original atomic theory, he stated that atoms of the same element are alike in weight and other properties and atoms of different elements are different in weight and other properties, that compounds are formed by the union or separation of definite numbers of atoms, and that atoms don't divide in chemical reactions, only whole atoms unite with other atoms. His version of the atomic theory is a theory due to the fact that it has been proved false.

• J.J. Thomson- Discovered the electron during his explorations of the properties of cathode rays.

• Ernest Rutherford- Discovered the proton by means of the gold foil experiment.

• Neils Bohr- Stated that electrons moved around the nucleus and also absorbed radiation as they changed state.

• Chadwhick- Discovered the neutron. Chadwick used scattering data to calculate the mass of this neutral particle.

• Otto Hahn- Discovered nuclear fission where the nucleus of the atom breaks up into different nuclei.

2.)Why were they vital to the development of the atom?

All the scientist's individual contributions were key in the perfecting of the atomic theory. The original was proposed by Democritus and it was left for the rest to find errors in each others and prove other parts right in order to improve it.

3.)What made them different if anything?

Some of the theories were based on correction of others and the other ones were based on the individuals own ideas mixed with the prior scientists knowledge.

4.)Think about your lessons in history and discuss how the time period that they lived in determined the outcome of their discovery/ or how it influenced those individuals to be the names that we know today (aka did it matter where they grew up or if they had money?)

Most people would say that it would be easier for the scientist if he had more money an therefore better equiptment, but i believe that its based more on the intellegence of the individual and what they make of their own situation. Their ideas were probly not even accepted as soon as the discovered it and therefore they would not become wealthy from it.

5.)Why do we consider the atomic theory still a theory? What are the new developments- would love for you to share new sources here about what you find?

We consider it a theory due to the fact that half of it has been proved incorrect, such as that atoms are indivisible. The atomic bomb is based on the spliting of an atom.

6.)Why does it matter that we understand the structure of the atom?

To better understand the world we live in and how or why things happen, we need to understand atoms, which are the basic building blocks of all matter.

The Atomic Theory

The Theory of the atom, or Atomic Theory, is the theory that all states of matter were composed of tiny particles called atoms. It was formulated by Democritus, and later worked on by Lavoisier and Dalton.


1.
The main people behind the development in the atom was Antoine Lavoisier who developed the law of conservation of mass which states mass cannot be lost through reactions. The other person who helped the development was John Dalton who said that one can combine two elements to create a more than one compound. He also said that each chemical element is composed of atoms that cannot be altered or changed. Another is J.J. Thompson who was the man who discovered the electron. Then Ernest Rutherford said that most of the atoms mass comes from the middle part of the atom also known as the nucleus.


2.
They all developed parts that others could not find or did not think of. They also helped proved that there was actually a small particle the composed all states of matter. They also showed that it wasn't just a whole particle but three different types of sub-particle inside the atom. They also describe how the atom worked so they could work further into learning about how the atom helped piece the world together.


3.
The only thing that made them different from each was how they went about and did the experiments, and what they thought the atom was composed of other than that nothing. Maybe a motive or a cause.

Development of the atom!!!!!!!!!!!

The atomic theory, was proposed in the 5th century. B.C. by the Greek philosophers Leucippus and Democritus and was adopted by the Roman Lucretius. But it was ignored for many centuries. Interest in the atomic theory was revived during the 18th century following work on the nature and behavior of gases.

1. Who were the main characters in the development of the atom?

Modern atomic theory begins with John Dalton. He held that all the atoms of an element are of exactly the same size and weight and are in these two respects unlike the atoms of any other element. He stated that atoms of the elements unite chemically in simple numbers to form compounds. The best evidence for his theory was the experimentally verified law of simple multiple proportions, which gives a relation between the weights of two elements that combine to form different compounds.

Evidence for Dalton's theory also came from Michael Faraday's law of electrolysis. A major development was the periodic table, devised simultaneously by Dmitri Mendeleev and J. L. Meyer, which arranged atoms of different elements in order of increasing atomic weight so that elements with similar chemical properties fell into groups. By the end of the 19th century it was generally accepted that matter is composed of atoms that combine to form molecules.

In 1911, Ernest Rutherford developed the first explanation of the structure of an atom. Using alpha particles emitted by radioactive atoms, he showed that the atom consists of a central core, called the nucleus, and negatively charged particles called electrons that orbit the nucleus. There was one serious obstacle to acceptance of the nuclear atom. According to classical theory, as the electrons orbit around the nucleus, they are continuously being accelerated, and all accelerated charges radiate electromagnetic energy. which, they should lose their energy and spiral into the nucleus.

This difficulty was solved by Niels Bohr (1913), who applied the quantum theory developed by Max Planck and Albert Einstein to the problem of atomic structure. Bohr proposed that electrons could circle a nucleus without radiating energy only in orbits for which their orbital angular momentum was an integral multiple of Planck's constant, divided by 2π. The discrete spectral lines emitted by each element were produced by electrons dropping from allowed orbits of higher energy to those of lower energy, the frequency of the photon of light emitted being proportional to the energy difference between the orbits.

Around the same time, experiments on x-ray's by H. G. J. Moseley showed that each nucleus was characterized by an atomic number, equal to the number of unit positive charges associated with it. By rearranging the periodic table according to atomic number rather than atomic weight, a more systematic arrangement was obtained. The development of quantum mechanics during the 1920s resulted in a satisfactory explanation for all phenomena related to the role of electrons in atoms and all aspects of their associated spectra. With the discovery of the neutron in 1932 the modern picture of the atom was complete.

2. Why were they vital to the development?

Each one of them put in there own thought and ideas into the atom at different time in life. They were all from different parts of the world at different times and different technology. With all of there ideas it eventually brought us to what the atom is today.

3. What made them different if anything?

They all didnt think the one before them was right, they believed there was more to the atom and kept testing ideas to make a better understanding of the atom and how it works. They all had different technology at the time they were alive making some things more testable and possible than others

.

The atom By Briana Lina

The idea that matter is made up of infinitely small, absolutely simple, indivisible pieces is hardly new. The Greek thinkers Leucippus and Democritus suggested the idea a good 100 years before Aristotle declared it was nonsense. However, the idea has only carried scientific weight for the past 200 years, and it only really took off in the past century.
Thompson’s “Plum Pudding” Model
The first major discovery that set off modern atomic theory was that atoms aren’t in fact the smallest things that exist. J. J. Thompson discovered the electron in 1897, which led him to posit a “plum pudding” model (a.k.a. the “raisin pudding” model) for the atom. Electrons are small negative charges, and Thompson suggested that these negative charges are distributed about a positively charged medium like plums in a plum pudding. The negatively charged electrons would balance out the positively charged medium so that each atom would be of neutral charge.

Rutherford’s Gold Foil Experiment
In a series of experiments from 1909 to 1911, Ernest Rutherford established that atoms have nuclei. His discovery came by accident and as a total surprise. His experiment consisted of firing alpha particles, which we will examine in more detail shortly, at a very thin sheet of gold foil. Alpha particles consist of two protons and two neutrons: they are relatively massive (about 8000 times as massive as an electron), positively charged particles. The idea of the experiment was to measure how much the alpha particles were deflected from their original course when they passed through the gold foil. Because alpha particles are positively charged and electrons are negatively charged, the electrons were expected to alter slightly the trajectory of the alpha particles. The experiment would be like rolling a basketball across a court full of marbles: when the basketball hits a marble, it might deflect a bit to the side, but, because it is much bigger than the marbles, its overall trajectory will not be affected very much. Rutherford expected the deflection to be relatively small, but sufficient to indicate how electrons are distributed throughout the “plum pudding” atom.
To Rutherford’s surprise, most of the alpha particles were hardly deflected at all: they passed through the gold foil as if it were just empty space. Even more surprising was that a small number of the alpha particles were deflected at 180º, right back in the direction they came from. This unexpected result shows that the mass of an atom is not as evenly distributed as Thompson and others had formerly assumed. Rutherford’s conclusion, known as the Rutherford nuclear model, was that the mass of an atom is mostly concentrated in a nucleus made up of tightly bonded protons and neutrons, which are then orbited by electrons. The electromagnetic force pulls the electrons into orbit around the nucleus in just the way that the gravitational force pulls planets into orbit around the sun.
The radius of an atom’s nucleus is about 1⁄10,000 the radius of the atom itself. As a result, most of the alpha particles in Rutherford’s gold foil experiment passed right through the sheet of gold foil without making contact with anything. A small number, however, bumped into the nucleus of one of the gold atoms and bounced right back.

Atom

In my opinion there were five main contributors to the evolution of the atom model. Without all these great researchers we would not have a great understanding of atoms.

Democritus- He was a Greek philosopher who developed the atomic theory of the universe. He also was the first one to come up with the term "Atom" from two Greek words meaning invincible.

John Dalton- A British physicist and chemist and contributed greatly to the development of the atomic theory. His theory stipulated that matter was made up of atoms of different weights and combine in simple ratios by weight. This idea is the basis of modern physical science.

Pierre and Maria Currie are well known in the area of science. Their contribution was that radioactive materials cause atoms to break down spontaneously and release radiation in the form of subatomic particles and energy.

Ernest Rutherford, in my opinion, is the scientist that contrubted the most. He was fundamental in the area of nuclear physics by discovering alpha and beta radiation, naming the nucleus and proton and predicted the presence of the neutron. His model of the atomic structure became the accepted model. He won the Nobel Prize in chemistry for explaining radioactivity as disintegration of atoms.

Niels Bohr was also fundamental in atomic work. He contributed explanations of the nuclear model by discovering that electrons orbited around an atom's nucleus and that they emitted or abosorbed energy. He was a student and then colleague of Ernest Rutherford and also won a Nobel prize.

Basic Unit of Matter

Who were the main characters in the development of the atom? Why were they vital to the development of the atom? What made them different if anything?

1.

Not until around 460 B.C., did a Greek philosopher, Democritus, develop the idea of atoms.

In the 1800's an English chemist, John Dalton performed experiments with various chemicals that showed that matter, indeed, seem to consist of elementary lumpy particles (atoms). Although he did not know about their structure, he knew that the evidence pointed to something fundamental.

In 1897, the English physicist J.J. Thomson discovered the electron and proposed a model for the structure of the atom. Thomson knew that electrons had a negative charge and thought that matter must have a positive charge.

In 1912 a Danish physicist, Neils Bohr came up with a theory that said the electrons do not spiral into the nucleus and came up with some rules for what does happen. (This began a new approach to science because for the first time rules had to fit the observation regardless of how they conflicted with the theories of the time.)

2.

Every person had a role in coming up with developments to the atom we know today.

Some more than others just cause the time period people were involved in creating their ideas.

3.

Every scientist is different; from where they come from or the way they thought about things. They all had different ideas about the atom.

THE ATOM!!! DUM DUM DUM.............

So yea, the atom, what is it? I could use fancy smancy words for it, or i could just tell you how it goes. Everything is made up of small things, which are called atoms. The first to discover the atom, and publish there findings were. Even though it is thought that Lavoisier was the first discoverer of atoms, i believe that in 1803 Dalton discovered that atoms were indivisible undiscrtutable balls.
The next part to the atom discovery is this: in 1897 J.J. Thompson measured the the charge to the mass ratio for a stream of electrons. He did this by using a cathode ray tube apparatus.
Thompson was able to determine the charge to mass ratio, BUT WAS NOT ABLE TO DETERMINE THE ACTUAL MASS OF AN ELECTRON.
In 1909 Robert Millikan dicovered the the charge of a single electron.
In about a difference of about 10 years, there was 2 different examples of how 2 different people thought the atom may have looked like.
J.J. Thompson's atom: " the plumb pudding model ", The whole atom was a circle of positive charge cloud like things, with little negetively charged electrons all in it.
Rutherford's idea of an atom was a little different: it was understood to be a little small dense ball in the center, and and all around it just empty space, and then with a little negative charged ring around it all.
In 1919 Rutherford discovered the posotively charged thing in the nucleus, protons
In 1932 Chadwick discovered the neutral particles in the nucleus, neutrons.