Cstclairdrake.net -

Assignments --> Scientists and also Organization the atoms


look here listed below for questions and info

Atomic theory Models evaluation Questions



1. That was Democritus?

2. Exactly how did Democritus reason for the visibility of atoms?

3. Just how did Democritus define atoms?

4. Discuss how fine Democritus’ ideas around atoms have sustained the test of time.

You are watching: John dalton reasoned that atoms exist from the evidence that

5. Iron and also lead are bothmetals, yet iron is lot harder than lead. Just how do girlfriend think Democritus could have described this difference?



1. Who was man Dalton?

2. What proof did Dalton usage to argue because that the visibility of atoms?

3. State Dalton’s atomic theory.

4. Explain how Dalton modeled atoms and also compounds.

Thomson’s atom Model


1. Who was J. J. Thomson?

2. Define how Thomson uncovered negatively fee particles smaller sized than atoms.

3. Thomson compared his idea ofatomic structureto a plum pudding. Create an original analogy because that Thomson’s plum pudding model of the atom.

4. Why to be Thomson’s model soon rejected?

Rutherford’s atom Model


1. Exactly how did Ernest Rutherford discover the cell core of the atom?

2. Place Rutherford’s exploration in the wider history that the atom. (Hint:See the timeline at the complying with URL for much more information:http://www.clickandlearn.org/gr9_sci/atoms/modelsoftheatom.html.)

3. Describe how you could make a three-dimensional version of Rutherford’s planetary version of the atom.

Bohr'sAtomic Model


1. Just how does Bohr’s atomic model construct on Rutherford’s model?

2. Explain the connection between energy quanta and energy levels.

3. How does Bohr’s work demonstrate the prestige ofcommunication in science?

Electron Cloud atom Model


1. What is the trouble with Bohr’s version of the atom?

2. Exactly how did Schrödinger resolve this problem?

3. Define orbitals.

4. Rundown the electron cloud version of the atom.

Democritus' Idea the the Atom

Introduces the idea of the atom together the basic, indivisible building block matter.

· testimonial how and when Democritus arrived at his idea the the atom.

· describe the atom as Democritus taken it.

· State how Democritus defined the diversity of matter.

· describe why Democritus’ idea was ignored until about 1800.


The guy shown over has been dubbed the “laughing philosopher” since of his please disposition. He absolutely looks you re welcome in this picture. Why is a philosopher featured in a science text? that made an remarkable contribution to science, return it to be ridiculed by others and also then ignored for an ext than 2000 years. His surname was Democritus, and he presented the idea that the atom as the an easy building block of all matter. You have the right to learn about Democritus’ location in the background of the atom in ~ this URL:


Cutting the Cheese

Democritus resided in Greece from around 460 to 370 B.C.E. Like countless other old Greek philosophers, he spent a most time wondering about the organic world. Democritus wondered, for example, what would happen if you reduced a chunk the matter—such together a piece of cheese into smaller and also smaller pieces. He believed that a allude would be got to at which the cheese might not be reduced into still smaller sized pieces. He dubbed these piecesatomos, which method “uncuttable” in Greek. This is whereby the modern-day termatomcomes from. In the video at the adhering to URL, bill Nye the Science guy demonstrates just how Democritus came down on his idea that the atom.



Just a Guess

Democritus’ idea that the atom has been referred to as “the ideal guess in antiquity.” That’s due to the fact that it to be correct in countless ways, yet it was based on pure speculation. It yes, really was just a guess. Here’s what Democritus thought about the atom:

· all matter consists ofatoms, which cannot be further subdivided right into smaller particles.

· atoms are very small—too little to see.

· Atoms are solid corpuscle that room indestructible.

· Atoms space separated indigenous one another by emptiness, or “void.”

Q:How room Democritus’ ideas aboutatomssimilar to modern-day ideas around atoms?

A:Modern ideas agree the all issue is made up of extremely tiny building block calledatoms.

Q:How are Democritus’ principles different from contemporary ideas?

A:Although atom are incredibly small, it is now feasible to see them with very powerfulmicroscopes. Atoms also aren’t the solid, uncuttable particles Democritus thought. Instead, lock consist of numerous kinds the smaller, easier particles as well as a many empty space. In addition, atoms aren’t yes, really indestructible because they can be adjusted to other creates of issue orenergy.

Keep top top Moving

Did girlfriend ever an alert dust motes relocating in tho air whereby a beam of sunshine passes with it? You deserve to see an instance in the woodland scene in theFigurebelow. This kind ofobservationgave Democritus the idea the atoms are in constant, arbitrarily motion. If this were true, Democritus thought, climate atoms must constantly be bumping right into each other. As soon as they do, that surmised, they one of two people bounce personal or stick with each other to form clumps the atoms. Eventually, the clumps could grow large enough come be visible matter.


Q:Which contemporary theory of matter is similar to Democritus’ ideas about the activity of atoms?

A:The modernkinetic concept of matteris remarkably similar to Democritus’ ideas around the motion of atoms. According to this theory, atom of issue are in continuous random motion. This activity is better ingasesthan inliquids, and also it is higher in liquids 보다 insolids. But even in solids, atoms room constantly vibrating in place.

Why issue Varies

Democritus believed that various kinds of issue vary because of the size, shape, and also arrangement of your atoms. For example, he suggested that sweetsubstancesare make of smooth atoms and also bitter substances room made of sharp atoms. That speculated the atoms ofliquidsare slippery, which permits them to slide over each other and liquids come flow. Atoms ofsolids, in contrast, stick together, therefore they cannot move apart. Distinctions in the weight of matter, that argued, could be described by the closeness that atoms. Atoms of lighter matter, he thought, were an ext spread out and separated by an ext empty space.

Q:Democritus thought that different kinds the atoms consist of different species of matter. How is this comparable to modern ideas about atoms?

A:The modern view is the atoms that differentelementsdiffer in their numbers ofprotonsandelectronsand this gives them different physical and chemical properties.

That’s Ridiculous!

Democritus was an important philosopher, however he to be less prominent than another Greek philosopher called Aristotle, who lived around 100 year after Democritus. Aristotle rubbish Democritus’ idea that the atom. In fact, Aristotle assumed the idea to be ridiculous. Unfortunately, Aristotle’s opinion was embraced for more than 2000 years, and Democritus’ idea was much more or much less forgotten. However, the idea the the atom was revitalized around 1800 by the English scientist man Dalton. Dalton developed an entire theory around the atom, lot of i m sorry is still welcomed today. That based his theory on experimental evidence, not on lucky guesses.


· about 400 B.C.E., the Greek thinker Democritus introduced the idea of the atom together the simple building block matter.

· Democritus assumed that atoms room tiny, uncuttable, solid particles that space surrounded by empty space and constantly moving at random.

· Democritus surmised that different kinds of issue consist the different species or arrangements of atoms.

Explore More

Watch the video at the adhering to URL, and also then develop ahypothesisto define the outcomes of the 2 experiments. Relate your hypothesis to Democritus’ ideas around atoms.



1. That was Democritus?

How go Democritus factor for the presence of atoms?How go Democritus describe atoms?Discuss exactly how well Democritus’ ideas about atoms have sustained the test of time.

Dalton's atom Theory

Pioneering job-related in the advance of modern understanding that the atom.

· define why Dalton reintroduced the idea the the atom.

· State Dalton’s atom theory.

· describe Dalton’s billiard ball version of the atom.


You probably recognize what this lay out represents. It’s a design of one atom, among the miniscule particles that consist of all matter. The idea that matter consists of incredibly tiny corpuscle calledatomswas first introduced around 2500 years earlier by a Greek philosopher called Democritus. However, other philosophers thought about Democritus’ idea ridiculous, and it was more or less forgotten for much more than 2000 years.

Reintroducing the Atom

Around 1800, the English chemist john Dalton brought back Democritus’ ancient idea that the atom. You have the right to see a snapshot of Daltonbelow. Dalton prospered up in a working-class family. Together an adult, that made a living by teaching and also just did research study in his preventive time. Nonetheless, from his research he emerged one of the most vital theories in every one of science. Based on his research results, he to be able to demonstrate thatatomsactually do exist, something that Democritus had only guessed.


Dalton’s Experiments

Dalton did plenty of experiments that detailed evidence for the visibility ofatoms. For example:

· the investigated pressure and also other nature ofgases, indigenous which that inferred that gases must consist of tiny, individual corpuscle that room in constant, arbitrarily motion.

· that researched the properties ofcompounds, i beg your pardon aresubstancesthat consist of much more than one element. He verified that a provided compound is always comprised that the sameelementsin the exact same whole-number ratio and that different compounds consist of different aspects or ratios. This can happen, Dalton reasoned, only if elements are make of separate, discrete particles the cannot it is in subdivided.

Atomic Theory

From his research, Dalton arisen a theory about atoms. Dalton’s atom theory consists of three simple ideas:

· Allsubstancesare do of atoms. Atoms are the smallest particles the matter. They cannot be split into smaller sized particles, created, or destroyed.

· every atoms of the same element are alike and have the very same mass. Atoms of differentelementsare different and also have different masses.

· Atoms join together come formcompounds, and also a offered compound constantly consists that the exact same kinds of atoms in the exact same proportions.

Dalton’s atomic theory was accepted by countless scientists almost immediately. Many of the is still embraced today. However, researchers now know that atoms are not the smallest particles of matter. Atoms consist the several types of smaller particles, includingprotons,neutrons, andelectrons. Because that the earlier story ~ above Dalton’s ideas about atoms and his ar in the background of the atom, clock this video:http://www.youtube.com/watch?v=BhWgv0STLZs(9:03).

For a musical version of the background of the atom, listen to “Atom Song” at this URL:http://www.youtube.com/watch?v=0P3m_L-myog(3:29).

The Billiard sphere Model

Because Dalton thought atoms were the the smallest particles the matter, he envisioned them as solid, difficult spheres, favor billiard (pool) balls, for this reason he used wooden balls to model them. Three of his design atoms space pictured in theFigurebelow. Do you check out the holes in the balls? Dalton added these therefore the design atoms can be joined together with hooks and also used come modelcompounds.


Q:When scientists found smaller particles within the atom, they realized the Dalton’s atom models were also simple. Exactly how do contemporary atomic models differ from Dalton’s models?

A:Modern atom models, choose the one pictured in ~ the top of this article, usually stand for subatomic particles, includingelectrons,protons, andneutrons. Because that a fuller compare of Dalton’s concepts and modern-day ideas, walk to this URL:



· around 1800, the English chemist john Dalton reintroduced the idea that the atom, i beg your pardon was an initial introduced by the old Greek philosopher named Democritus.

· Dalton did plenty of experiments withgasesand compounds that provided evidence because that the visibility of atoms.

· Dalton developed an atomic concept that is still mostly embraced today. It is just one of the most essential theories in all of science.

· Dalton believed individual atoms to be solid, hard spheres, so he modeled them with wooden balls.

Explore More

Read the article about Dalton’s atomic concept at the complying with URL. Climate take the online quiz. Be certain to inspect your answers and also read the explanations for any kind of incorrect answers.



5. That was man Dalton?

6. What evidence did Dalton usage to argue because that the visibility of atoms?

7. State Dalton’s atomic theory.

8. Define how Dalton modeled atoms and also compounds.

Thomson's atomic Model

Discovery the the electron and the plum pudding design of the atom.

· define how J. J. Thomson uncovered the electron.

· explain Thomson’s plum pudding model of the atom.


You probably recognize that the wires strung in between these high towers lug electricity. Yet do you recognize what electricity is? it actually is composed of a constant stream of small particles calledelectrons. Electrons space negatively chargedfundamental particlesinsideatoms. Atoms to be discovered roughly 1800, but virtually 100 years went by before electrons were discovered.  

Thomson DiscoversElectrons

John Dalton discoveredatomsin 1804. He assumed they to be the the smallest particles that matter, which might not be damaged down right into smaller particles. That envisioned them together solid, difficult spheres. The wasn’t till 1897 that a scientist named Joseph john (J. J.) Thomson uncovered that over there are smaller sized particles in ~ the atom. Thomson to be born in England and also studied at Cambridge University, wherein he later came to be a professor. In 1906, he won the Nobel prize in physics because that his research on howgasesconduct electricity. This research likewise led come his discovery of the electron. You can see a snapshot of Thomsonbelow. You can take a museum tour of his discovery at this virtual exhibit:http://www.aip.org/history/electron/.


Thomson’s Experiments

In his research, Thomson passed present through acathode ray tube, similar to the one seen in theFigurebelow. Acathode ray tubeis a glass pipe from i beg your pardon virtually every one of the air has been removed. It has a item of metal referred to as an electrode at each end. One electrode is negative charged and also known as a cathode. The various other electrode is positively charged and also known together an anode. Once high-voltageelectric currentis used to the end plates, a cathode beam travels from the cathode to the anode.

What is a cathode ray? That’s what Thomson wanted to know. Is it just a beam ofenergythat travel in waves choose a ray of light? the was one popularhypothesisat the time. Or was a cathode beam a present of relocating particles? that was the other popular hypothesis. Thomson tested these concepts by placing negative and hopeful plates follow me the political parties of thecathode ray tubeto see how the cathode ray would be affected. The cathode ray appeared to it is in repelled by the negative plate and also attracted through the optimistic plate. This intended that the beam was an unfavorable in charge and that is should consist of corpuscle that have actually mass. He dubbed the corpuscle “corpuscles,” but they were later on renamedelectrons. For a video clip demonstration of Thomson’s experiment, go to this URL:http://ericsaltchemistry.blogspot.com/2010/10/jj-thomsons-experiments-with-cathode.html.


Thomson likewise measured the mass of the particles he had identified. That did this by determining just how much the cathode rays to be bent as soon as he varied thevoltage. He uncovered that the mass of the particles was 2000 times smaller sized than the massive of the smallest atom, the hydrogen atom. In short, Thomson had uncovered the existence of particles smaller sized thanatoms. This disproved Dalton’s case that atoms room the the smallest particles the matter. From his discovery, Thomson likewise inferred the electrons arefundamental particleswithin atoms.

Q:Atoms are neutral in electrical charge. How can they it is in neutral if lock contain negatively charged electrons?

A:Atoms additionally contain positively charged particles that cancel the end the an adverse charge of the electrons. However, these optimistic particles weren’t discovered until a pair of years after Thomson found electrons.

The Plum Pudding Model

Thomson likewise knew that atoms space neutral in electric charge, for this reason he request the exact same question: How have the right to atoms contain an adverse particles and also still it is in neutral? he hypothesized that the remainder of the atom should be positively charged in order come cancel the end the negative charge the the electrons. He envisioned the atom as being similar to a plum pudding, prefer the one pictured in theFigurebelow—mostly positive in fee (the pudding) with negative electrons (the plums) scattered through it.


Q:How is our modern understanding ofatomic structuredifferent indigenous Thomson’s plum pudding model?

A:Today we know that all of the optimistic charge in one atom is concentrated in a tiny main area dubbed the nucleus, v the electrons swirling v empty room around it, together in theFigurebelow. The cell core was uncovered just a few years ~ Thomson uncovered the electron, for this reason the plum pudding design was soon rejected.



· In 1897, J. J. Thomson discovered the first subatomic particle, the electron, while researching cathode rays.

· To describe the neutrality of atoms, Thomson propose a version of the atom in which an adverse electrons are scattered throughout a sphere of hopeful charge. He referred to as his atom the plum pudding model.

Explore More

Watch this comprehensive presentation about J. J. Thomson’s exploration of the electron, and also then prize the inquiry below.


1. Thomson not only discovered that a cathode ray consists of flow negatively charged particles the are smaller sized than atoms. He likewise made the logical leap the these particles help make increase atoms. What thinking did Thomson usage to do this inference?


5. Who was J. J. Thomson?

6. Define how Thomson uncovered negatively charged particles smaller than atoms.

7. Thomson compared his idea ofatomic structureto a plum pudding. Create an initial analogy for Thomson’s plum pudding model of the atom.

8. Why was Thomson’s design soon rejected?

Rutherford's atomic Model

Discovery of the nucleus and also the planetary design of the atom.

· define how Ernest Rutherford found the cell core of the atom.

· describe Rutherford’s planetary version of the atom.


Thom is shooting baskets. He’s trying to hit the backboard therefore the sphere will bounce off it and into the basket. If only the backboard was bigger! It would be a lot less complicated to hit. If the ball misses the backboard, that will simply keep going and Thom will need to run after it. Believe it or not, the research that caused the discovery of the nucleus of the atom to be a tiny like shooting baskets.  

Narrowing under the Nucleus

In 1804, practically a century prior to the nucleus was discovered, the English scientist john Dalton noted evidence because that the existence of the atom. Dalton assumed thatatomswere the the smallest particles of matter, i m sorry couldn't be separated into smaller particles. That modeled atoms with solid wood balls. In 1897, an additional English scientist, named J. J. Thomson, found the electron. The was first subatomic fragment to it is in identified. Since atoms space neutral in electrical charge, Thomson assumed that atoms must also contain areas of positive charge to cancel out the negatively chargedelectrons. He thought that one atom was choose a plum pudding, consisting mainly of positive charged matter with an unfavorable electrons scattered v it.

The cell core of the atom was found next. It was found in 1911 by a scientist from brand-new Zealand called Ernest Rutherford, that is pictured inFigurebelow. With his clever research, Rutherford confirmed that the hopeful charge of one atom is confined come a tiny massive region at the facility of the atom, rather than being spread evenly throughout the “pudding” of the atom together Thomson had suggested. You can watch a video about Rutherford and also his exploration at this URL:



Go for the Gold!

The method Rutherford uncovered theatomic nucleusis a great example of the duty of imagination in science. His search actually began in 1899 once he found that someelementsgive off positively fee particles that deserve to penetrate just around anything. He called these particles alpha (α) corpuscle (we now recognize they to be helium nuclei). Like all an excellent scientists, Rutherford was curious. That wondered just how he could use alpha corpuscle to learn around the framework of the atom. He decided to target a beam the alpha corpuscle at a paper of an extremely thin gold foil. He chose gold since it can be pounded into sheets that are just 0.00004 cm thick. Neighboring the sheet of gold foil, he inserted a screen that glowed when alpha corpuscle struck it. It would certainly be offered to detect the alpha corpuscle after they passed through the foil. A little slit in the screen enabled the beam that alpha particles to with the silver paper from the bit emitter. You have the right to see the setup because that Rutherford’s experiment in theFigurebelow.

Q:What would you suppose to happen when the alpha corpuscle strike the gold foil?

A:The alpha corpuscle would permeate the gold foil. Alpha particles room positive, so they could be repelled by any kind of areas of positive charge within the goldatoms.


Assuming a plum pudding design of the atom, Rutherford predicted the the areas of positive charge in the goldatomswould deflect, or bend, the path of every the alpha particles together they pass through. You deserve to see what really occurred in theFigureabove. Many of the alpha particles passed straight through the yellow foil together though that wasn’t there. The particles appeared to it is in passing with empty space. Only a couple of of the alpha particles to be deflected from their straight path, together Rutherford had actually predicted. Surprisingly, a tiny portion of the corpuscle bounced back from the foil prefer a basketball bouncing turn off a backboard! You can see an animation of this experiment at the following URL:http://www.clickandlearn.org/gr9_sci/atoms/modelsoftheatom.html.

Q:What deserve to you infer from this observations?

A:You deserve to infer that many of the alpha particles were no repelled by any positive charge, conversely, a few were repelled by a solid positive charge.

The cell nucleus Takes facility Stage

Rutherford made the exact same inferences. He concluded that every one of the hopeful charge and also virtually all of the massive of one atom are focused in one tiny area and also the remainder of the atom is mostly empty space. Rutherford referred to as the area of concentrated positive fee the nucleus. The predicted—and shortly discovered—that the nucleus contains positively fee particles, which that namedprotons. Rutherford additionally predicted the visibility of neutral nuclear particles calledneutrons, however he failed to discover them. However, his student James Chadwick discovered them numerous years later. You have the right to learn how at this URL:http://www.light-science.com/chadwick.html.

The Planetary Model

Rutherford’s explorations meant the Thomson’s plum pudding model was incorrect. Optimistic charge is not spread out evenly transparent an atom. Instead, the is all concentrated in the small nucleus. The remainder of the atom is empty room except because that theelectronsscattered with it. In Rutherford’s design of the atom, i m sorry is presented in theFigurebelow, theelectronsmove around the huge nucleus favor planets orbiting thesun. That’s why his version is referred to as the planetary model. Rutherford didn’t know specifically where or just how electrons orbit the nucleus. That study would be undertaken by later scientists, start with Niels Bohr in 1913. New and boosted atomic models would also be developed. Nonetheless, Rutherford’s model is still often used to stand for the atom. You can see an animated variation of the model at this URL:http://www.clickandlearn.org/gr9_sci/atoms/modelsoftheatom.html.



· Ernest Rutherford found the cell nucleus of the atom in 1910. He sent a beam of alpha particles toward gold foil and also observed the method the particles were deflected by the yellow atoms. Indigenous his results, that concluded that all of the hopeful charge and virtually every one of the mass of an atom are concentrated in one tiny area, called the nucleus, and also the rest of the atom is greatly empty space.

· In Rutherford’s planetary design of the atom, the electrons move through empty space around the tiny optimistic nucleus like planets orbiting thesun.

Explore More

Watch this video about Rutherford’s gold foil experiment, and also then price the inquiries below.


1. Exactly how did Rutherford watch alpha particles in his experiment? In the modern version that Rutherford’s experiment, i m sorry is presented in the video, exactly how are alpha corpuscle observed? Which method do you think is an ext accurate?

2. Based upon the computer animation in the video, attract a sketch showing what wake up to alpha particles as they pass through gold atoms.

3. How has actually Rutherford’s gold foil experiment been adopted by modern researchers?


4. Just how did Ernest Rutherford uncover the nucleus of the atom?

5. Ar Rutherford’s discovery in the more comprehensive history the the atom. (Hint:See the timeline in ~ the complying with URL for more information:http://www.clickandlearn.org/gr9_sci/atoms/modelsoftheatom.html.)

6. Explain how you could make a three-dimensional variation of Rutherford’s planetary model of the atom.

Bohr's atomic Model

Model that the atom that introduces power levels where electrons are found.

· explain how Bohr modification Rutherford’s atom model.

· describe energy level inatomsin terms of energy quanta.


Look at the human being in the picture. Execute you see how they room standing on various rungs the the ladder? once you was standing on a ladder, you can stand on one rung or another, however you deserve to never stand in in between two rungs. A ladder deserve to be supplied to design parts of an atom. Perform you recognize how? review on to discover out.  

Modeling the Atom

The visibility of the atom was very first demonstrated approximately 1800 by john Dalton. Then, close come a century went by before J.J. Thomson discovered the an initial subatomic particle, the negatively charged electron. Becauseatomsare neutral in charge, Thomson thought that they must consist the a sphere of optimistic charge withelectronsscattered with it. In 1910, Ernest Rutherford confirmed that this idea to be incorrect. He prove that every one of the hopeful charge of an atom is actually concentrated in a tiny central region called the nucleus. Rutherford surmised the electrons move about the nucleus like planets about thesun. Rutherford’s idea ofatomic structurewas an innovation on Thomson’s model, however it wasn’t the last word. Rutherford focused on the nucleus and also didn’t really clarify whereby the electrons were in the empty an are surrounding the nucleus.

The next major advance in atomic background occurred in 1913, once the Danish scientist Niels Bohr published a description of a an ext detailed model of the atom. His model established more clearly whereelectronscould be found. Although later scientists would develop more refined atom models, Bohr’s model was basically correct and also much of it is still accepted today. It is also a very useful model due to the fact that it defines the properties of differentelements. Bohr received the 1922 Nobel prize in physics for his contribution to our expertise of the structure of the atom. You have the right to see a photo of Bohrbelow.

See more: How Tall Is 68 Inches In Ft, 68 In To Ft 68 Inches To Feet


On the Level

As a young man, Bohr operated in Rutherford’s lab in England. Since Rutherford’s model was weak ~ above the place of theelectrons, Bohr focused on them. He hypothesized the electrons deserve to move around the nucleus just at fixed distances from the nucleus based upon the amount of energy they have. He referred to as these fixed distances energy levels, or electron shells. He assumed of them as concentric spheres, with the nucleus in ~ the center of every sphere. In various other words, the shells consisted of sphere within round within sphere. Furthermore, electrons with less energy would be discovered at lower power levels, closer come the nucleus. Those with an ext energy would be discovered at higher energy levels, farther from the nucleus. Bohr likewise hypothesized that if one electron took in just the ideal amount that energy, it would jump to the following higherenergy level. Whereas if it lost the exact same amount that energy, it would jump earlier to that original power level. However, one electron could never exist in between two energy levels. These principles are shown in theFigurebelow.