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Chemistry > History Of The Atom > Flashcards

History Of The Atom Flashcards

1
Q

What is a atom

A

The smallest part of an element which still has the properties of that element

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2
Q

What is an Element

A

substance that cannot be broken down into anything simpler by chemical means

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3
Q

Matter

A

Anything which takes up space and has mass

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4
Q

What did the Greek philosophers propose

A

Matter was composed of small particles, these particles were so small they couldn’t be broken down into smaller particles

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5
Q

What did John Dalton develop

A

John Dalton developed the atomic theory

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6
Q

What is the atomic theory

A

All matter is made up of tiny invisible particles called atoms that can be neither created nor destroyed

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7
Q

Who conducted the first experiments on cathode rays

A

William crookes

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8
Q

What are the properties of cathode rays

A

Cathode rays travel in straight lines (sharp shadow)
Cathode rays cause glass to fluoresce when they strike it
Cathode rays have enough energy to move a paddle wheel

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9
Q

Who discovered electrons

A

JJ Thomson

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10
Q

What did JJ Thompson discover (in relation to the electron)

A

The charge to mass ratio

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11
Q

What model did JJ Thomson propose

A

The plum pudding model

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12
Q

Who discovered the exact charge of an electron

A

Robert Milikan

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13
Q

What experiment did Robert Milikan do to determine the exact charge of an electron ?

A

Oil droplet experiment

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14
Q

Who discovered the nucleus

A

Ernest Rutherford

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15
Q

Describe the golf foil experiment

A

Thin beam of alpha particles from a lead box with a sample of radium
Gold foil that acted as a thin layer of atoms
Detector screen
Very unexpected results

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16
Q

What model did Rutherford propose

A

Nuclear model

17
Q

Who discovered neutrons?

A

James Chadwick

18
Q

How did James Chadwick discover neutrons

A

By bombarding a beryllium sample with alpha particles, the neutrons were released at a detector / counter for protons

19
Q

What is the atomic mass of an electron

A

1/1840

20
Q

What are cathode rays

A

They are an electrical current coming from the negative end of a power supply

21
Q

What are alpha particles

A

Positivity charged particles from a radioactive source

22
Q

What was William Crookes investigating in the cathode ray expeirment

A

Investigate what happens when an electric current is passed through a gas tube containing air at low pressure (vacuum tube)

23
Q

Describe the cathode ray experiment done by crookes

A

Cathode rays came from the cathode end of a power source. He showed the existence of this radiation

24
Q

What was JJ Thompson investigating in his cathode ray expeirment

A

Investigated if the cathode rays discovered by crooked consisted of charged particles

25
Q

Describe the cathode ray expeirment done by JJ Thompson

A

Obtained a narrow beam of cathode rays by passing them through a small hole in the anode.
If there was no charge on the magnetic plates the beam passed in a straight line.
But since the cathode rays were attracted so the positive plate, he concluded they consisted of negatively charged particles

26
Q

Describe Thomsons plum pudding model

A

An atom is a sphere is positive charge. Electrons are embedded in the sphere at random. No evidence to prove

27
Q

Describe the oil drop experiment by Robert Millikan

A

Sprayed tiny droplets of oil between two charged metal plates.
Ionised air( molecules in air lost electrons). The oil drops picked up the electrons. The oils droplets became attracted to the positive plate. Adjusted charge until stationary

28
Q

Describe the expected results of the Gold foil by Ernest Rutherford

A

Based on Thomson’s plum pudding model, he predicted most of the atoms would pass straight through the gold foil. The positive charge would be too weak to affect the electrons

29
Q

Explain the expected results of the gold foil experiment

A

Based on the plum pudding model by JJ Thompson, he predicted most of the atoms would pass straight through the gold foil. The positive charge would be too weak to affect the electrons

30
Q

Describe the actual results of the gold foil experiment

A

While most of the alpha particles pass straight through the gold foil, a few alpha particles were deflected more than 90 degrees, and even smaller amount were deflected along the path they came from

31
Q

What conclusion did Ernest Rutherford derive from the results

A

The positive charge must be localised over a tiny volume of the atom, which contains most of the atoms mass.
Since most of the alpha particles pass straight through , the atoms must be mostly made up of empty space

32
Q

Describe the nuclear model

A

Positive nucleus with an electron cloud

Chemistry (15 decks)

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