Atomic Theories Flashcards

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1
Q

Scientific notation:

  1. 2 X 10^4
  2. 2 X 10^-4
A

62000

0.00062

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2
Q

What is an atom?

A

Smallest Particle of Matter

Cannot be divided chemically

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3
Q

Why do scientist create atomic models

A

To be able to study the atom (too small)

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4
Q

Democritus Discontinuous model

A

First use of word «atom»
Small invisible particles called atoms
Space between atoms
“Like sand on a beach”

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5
Q

Aristotle Continuous model

A

Matter is infinitely divisible

Solid with no space in between

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6
Q

John Dalton’s Atomic theory

A

1) all matter is composed of tiny indivisible particles called atoms (this was proven false as atoms are divisive into protons neutrons and electrons)
2) all atoms of same element are identical
3) different elements are composed of different size atoms which have their own properties
4) atoms combine to make molecules

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7
Q

JJ Thomson discovery

A

Cathode Rays (composed of electrons)

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8
Q

JJ Thomson experiment (setup)

A

Thomson used a cottage ray tube connected to a power supply. On one end was a cathode (negative) and an anode (positive).

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9
Q

JJ Thomson Experiment (result)

A

When connected to a power supply a beam appeared. This beam was either particles or light. When he put a propeller in, it started moving (it was particles). When Thomson out positively charged plates outside the tube, the rays would be attracted to them.

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10
Q

JJ Thomson experiment (conclusion)

A

There are negatively charged particles in an atom called electrons

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11
Q

Thompson’s model

A

Raisin Bun or Plum Pudding

Atom is divisible
Big positive with electrons in the middle

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12
Q

Alpha Particles
Beta Particles
Gamma Rays

A

Alpha=Positive
Beta= negative
Gamma Rays: No charge

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13
Q

Rutherford experiment

A

Aimed alpha particles (positive) at a price of gold with a detecting screen around.

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14
Q

Rutherford Experiemnt (results)

A

Most particles went straight through
Some were deflected
Very few bounced right back

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15
Q

Rutherford experiment (conclusions)

A

Atom is mostly empty space

Contains very dense and small numcleus

Nucleus is positively charged

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16
Q

Properties of protons (3)

A

Positive
Large mass
Found in nucleus (middle)

17
Q

Properties of electrons (3)

A

Negative charge
Small mass
Found on outside of nucleus

18
Q

Neils Bohr’s observation

A

Bohr studied the light emitted by elements when hot. He saw different colours. He figured out that electrons were not randomly distributed but they were put on different orbits of energy. When the electrons are heated, they jump to another level of energy. When they come back down, they emit light.

19
Q

Rutherford Bohr atomic model

A

Number of protons in middle (nucleus)
Number of electron shells surrounding nucleus
Number of electrons placed on shells

20
Q

James Chadwick doscivery

A

He discovered the neutron.

Neutron held the protons from repelling from each other.