Term
| During the eighteenth century, what did scientists discover? |
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Definition
| They found that certain substances couldn't be broken down. Atoms in the same element are all the same. |
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Term
| What did John Dalton propose? |
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Definition
1.) Matter is made up of atoms
2.) Atoms cannot be divided
3.) All atoms of one element are exactly alike
4.) Different elements are made of different kinds of atoms |
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Term
| English scientist William Crookes conducted experiments with cathode ray tubes (CRT's). What did he find? |
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Definition
| Shadow on anode showed Crookes that something was traveling from the cathode to the anode. He hypothesized that the glow was caused by rays (streams of particles). |
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Term
| J.J. Thomson also did experiments with ____'s. He placed a magnet by the tube, and found that the ray _ _ _ _, which proved it wasn't _ _ _ _ _. He concluded that the beam must be made up of charged _ _ _ _ _ _ _ _ _ of _ _ _ _ _ _. |
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Definition
CRT
bent
light
particles
matter |
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Term
Thomson inferred the following about electrons:
1.) they are part of every kind of _ _ _ _.
2.) they are _ _ _ _ _ _ _ _ _ _ charged.
He also discovered that _ _ _ _ _ _ _ _ _ smaller than the atom do exist. |
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Definition
1.) atom
2.) negatively
3.) particles |
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Term
| Describe Ernest Rutherford's experiment. |
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Definition
| He held an experiment with gold foil, where he shot a beam of positively charged particles through a thin sheet of gold foil. To his surprise, some of the beams darted off at large angles. He had only predicted that small angles would be formed (occasionally). |
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Term
| What was Ernest Rutherford's explanation for the unexpected results of his experiment? |
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Definition
| He hypothesized that all the protons in an atom are crammed into a tiny nucleus. Every once in a while, the nucleus would hit the gold foil head-on, and bounce off. Other times, the atom hit the gold foil in its electron cloud. |
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Term
| What was the proposition to the the problem of unexplained mass in atoms? |
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Definition
| Neutrons- they weigh the same as protons. |
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Term
| How did Niels Bohr contribute to the model of the atom? |
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Definition
| He calculated the energy levels the electrons would orbit the nucleus in, and the region in which they would probably move (which is actually probably correct). |
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Term
| Scientists concluded that it is impossible to calculate the exact _ _ _ _ _ _ _ _ of an electron at any point in time. |
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Definition
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Term
Vocabulary:
atomic number |
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Definition
| Number of protons in the nucleus of an atom of one element. |
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Term
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Definition
| Atoms that have different numbers of neutrons in the same element. |
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Term
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Definition
Number of neutrons plus protons.
N + P = M# |
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Term
Vocabulary:
Radioactive Decay |
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Definition
| Release of nuclear particles and energy. |
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Term
Vocabulary:
Transmutation |
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Definition
| Changing of one element into another through radioactive decay. |
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Term
| What is the difference between alpha particle decay and beta particle decay? |
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Definition
| An alpha particle is made up of two neutrons and two protons, and when it is lost, you find the new element by going down two atomic numbers. A beta particle is a high-energy electron that comes from the nucleus. When you lose a beta particle, you go up one atomic number, because you gain one proton when the neutron splits. |
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Term
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Definition
| The half-life of a radioactive isotope is the amount of time it takes for half of the sample to decay. |
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Term
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Definition
| Scientists can hypothesize at what time an animal lived by measuring the amount of carbon the corpse has inside it and comparing it to the amount it would have if it were alive. This only works for matter that has been alive. |
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Term
| Since they can't use carbon dating, how do scientists find the age of rocks? |
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Definition
| Scientists examine the decay of uranium; uranium is replaced by lead, so they compare these quantities. There is some controversy over whether this is an accurate measurement, because some rocks might have had lead in them to start out with. |
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