History of the Atom Flashcards
What did Mendeleyev do?
Found 60 element
How did Mendeleyev arrange the elements?
By atomic mass and similar c+p properties
What were Dalton’s 5 theories
- All matter is made of atoms
- Chemical reaction is a rearrangement of atoms
- Atoms of the same element are similar in shape/size
- Atoms combined in small whole number rations form compounds
What did Democritus do for the atom?
Created the concept of atomism (all matter is made up of tiny, indivisible particles (atoms))
What did JJ Thomson create
The Cathode Ray (sealed glass tube)
Describe JJ Thomson’s experiment
Put 2 magnets on either side of the sealed glass tube and found that the magnets deflected the cathode ray
What were JJ Thomson’s 3 discoveries?
- Cathode ray is made from negatively charged particles (electrons)
- Particles must exist as part of atom
- The subatomic particles can be found within atoms of all elements
What is JJ Thomson’s model called and what does it look like?
Plum Pudding Model and it looks like a chocolate chip cookie with positive and negative charges, the negative charges are the chocolate chips
What did Goldstein do?
Put the cathode in the middle of the tube instead of at the end
What did Goldstein discover?
Canal rays (positive charge rays (protons))
What did Becquerel discover?
Radioactivity
What was Becquerel’s hypothesis?
The sun made certain things radioactive
Describe Becquerel’s experiment
He put uranium salts on plates and found they turned the plates foggy showing radiation. He put them on windowsills so that they would be exposed to light (he thought that made them radioactive). On a foggy day, he put the salts in a drawer and found that they did make the plate foggy showing radiation (and how it is not related to sunlight) it was an accidental find
What are the 3 kinds of radioactive waves
Alpha, Beta, Gama
Properties of Alpha particles
1. Definition
2. Charge
3. Penetrating strength
4. Stopped by…
- Ionizing radiation with alpha particles
- Positive
- Least
- thick sheet of paper
Why did Curie name Radium that?
It is an element formed from radioactivity
Properties of Beta particles
1. Definition
2. Charge
3. Penetrating strength
4. Stopped by…
- Emitted from nucleus during radioactive decay
- Negative
- Middle
- Thin sheet of paper, aluminum
What advancement did Becquerel make?
The nucleus emits radiation, it transforms the nuclide
Properties of Gama particles
1. Definition
2. Charge
3. Penetrating strength
4. Stopped by…
- Smallest wave lengths- electromagnetic radiation
- no charge
- Most
- Lead only
What did Curie discover?
Radium and Polonium
Why did Curie name Polonium that?
She is from Poland
What did Roentgen do?
Made the first x-ray, wrapped cathode tube in black paper, saw glowing/light. First image was of his wife’s hand and you can see her ring
What experiment did Rutherford do?
The Gold Foil Experiment
Explain the Gold Foil Experiment
He took a piece of golf foil and hit alpha particles (+ charge) at it. Most alpha particles pass right through, but some deflected or were bent at large angles. This can only happen if the atom had a small, heavy region of protons inside it.
Why did Rutherford use Gold Foil
Because it was malleable and wanted the thinnest layer of metal. Also alpha particles can pass through thin things.
What model did Rutherford make and describe it
Planetary Model
- a tiny, dense, positively charged nucleus, mass of atom is concentrated in its nucleus and the electrons orbit around the nucleus
What is the question left after Rutherford’s experiment is completed?
Why are some alpha particles deflected and others aren’t?
Who used the mass spectrometer?
Aston
What did the mass spectrograph discover?
Nonradioactive isotopes (same elements different masses)
How does the spectrograph work?
It converts molecules into ions (the sample is a vapor) by the use of radioactivity which are then manipulated by electric and magnetic fields. The molecules are turned to ions by knocking off 1 or more electrons. The positive ions repel from the + side of the magnet on the bottom and attract to the - side of the magnet on the top causing the protons to curve upwards. When they deflect and his the photographic plate, the lighter ones showed to deflect more and the heavier ones deflected less.
What did the beams lading in certain spots show
Ions have only a certain mass
Who discovered the neutron
James Chadwick
Explain Chadwick’s experiment
He created the Beryllium Bombardment experiment. Alpha particles hit Beryllium and were turned to an unknown charge. They then hit Paraffin wax and turned to protons. He figured out that there are neutrons after the alpha particles hit the Beryllium.
Why does the discovery of Neutrons advance the model of the atom
It explains why protons can be by each other in the nucleus without repelling. The neutrons sperate them and the electrons keep them inside.
Describe the Millikan experiment
He diffused oil particles by the use of a atomizer. Only some passed through the tiny holes in the upper positively charged plate. The radioactive particles knocked off electrons from the air inside. These electrons attached to the oil particles that were falling because of gravity. The electrons repel from the negative charged plate on the bottom and are attracted to the positively charged plate on the top so they go up. Millikan changed the amount of force the plates gave off. Once the particles were in the middle of the container they were at equilibrium and that is when gravity is balanced by the force of the plates.
What is the equation used to find the electron charge
QE=MG
Q= electron charge of droplets
E= electric field
M=mass
G=gravity
the mass of the droplets is found by density (D=m/v) the volume of a spherical drop is v=4/3 pie r^3
What did they find when they solved for Q in the electron charge equation
Q was multiples of 1.06 times 10^-19. This represents 1 charge and it is negative because that shows how many electrons attached to the oil droplet in the experiment
What is light according to Bohr?
Tiny massless particles
What does quantized mean?
The smallest amount of energy that can be emitted or absorbed in the form of electromagnetic radiation
What is a photon
The massless particles found in light
What did Bohr conclude about electrons?
Electrons move around a nucleus, but only in prescribed orbits
Describe Bohr’s model
Rings that contain electrons around a dot (the nucleus)
What happens when electrons drop from the fourth shell of the hydrogen to the first shell of the hydrogen?
It looses energy and emits a photon (massless particles found in light (so it gives off light))
Which color has the shortest wavelength?
violet
Which color has the longest wavelength?
Red
Which color has the lowest energy?
Red
Which color has the highest energy?
Violet
How can light be separated according to its wavelengths?
What light is passed through a prism or spectrograph
