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Chemistry > The Evolution of the Atomic Model > Flashcards

The Evolution of the Atomic Model Flashcards

1
Q

What did the atomic model look like in 400BC?

A

like a billiard ball

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2
Q

What was Democritus’s theory about the atom?

A

Matter cannot be divided into smaller pieces forever. Eventually the smallest piece would be obtained, which would be indivisisble.

Atoms have different sizes, are in constant motion, and separated by empty space.

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3
Q

Democritus named the smallest piece of matter ________ meaning ______________

A

atomos, not to be cut

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4
Q

What did Aristotle propose?

A

that all matter is composed of four essential substances

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5
Q

What are the four essential substances Aristotle proposed?

A

Earth
Air
Water
Fire

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6
Q

What was John Dalton’s theory?

A
  • All matter is made up of tiny particles called atoms.
  • An atom cannot be created, destroyed or divided into smaller particles
  • The atoms of one element cannot be converted into the atoms of any other element
  • All the atoms of one element have the same properties, such as mass and size. These properties are different from the properties of the atoms of any other element
  • Atoms of different elements combine in specific proportions to form compounds
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7
Q

What was the experimental proof for Dalton’s Model?

A

Lavoisier - Law of conservation of mass
Proust - Law of constant composition

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8
Q

What is the law of conservation of mass?

A

mass of reactants must equal the mass of products - balanced equations

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9
Q

What is Proust’s Law of constant composition.

A

each atom has a particular combining capacity

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10
Q

Dalton believed atoms are not indivisiable

A

false

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11
Q

When were the series of experiments that demonstrated the atoms is made of smaller components performed?

A

betwee the 1850s to 1900

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12
Q

What were the three atom components discovered between the 1850s to 1900s?

A
  • electrons
  • protons
  • neutrons
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13
Q

What did J.J THomson study? What did he discover?

A

the passage of an electric current through a gas. As the current passed through the gas, it gave off rays of negatively charged particles.

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14
Q

Who discovered electrons? What were they called at the time?

A

J.H Thomson, they were called corpuscles.

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15
Q

What did J.J Thomson conclude from his experiments?

A

that negative charges come from within the atom so a smaller particle than the atom had to exist. The gas was also known to be neutral so there had to be something positive balancing out the negative particles.

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16
Q

What was Thomson’s model? And what year was it presented in?

A

“plum pudding” model in 1897

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17
Q

Describe the structure of the plum pudding model.

A

atoms were made of a positively charged substance with negatively charged electrons scattered about like raising in a pudding

18
Q

What was Ernest Rutherford’s experiment? What was it’s purpose?

A

The Gold Foil Experiment - to test Thomson’s model

19
Q

Describe the Gold Foil Experiment.

A

alpha particle was shot through a small hole in lead at gold foil.
- measured how much the gold foil deflected the alpha particles. The surrounding screens glowed where the alpha particles hit.

20
Q

What were the expectations of the gold foil experiment?

A
  • If electrons were equally distributed throughout the atom, the positively charged alpha particles should pass straight through the gold foil
  • there would be little to no deflection
21
Q

What were the experimental findings of the gold foil experiment?

A
  • Most of the positively charged ‘bullets’ passed right through the gold foi without changing course at all
  • sme of the alpha particles bounced away from the gold sheet as if they had hit something solid.
  • Rutherford knew that positive charges repel positive charges
22
Q

What were the conclusions of the gold foil experiment?

A
  • glod atoms in the sheet were mostly open space
  • an atom had a small, dense, positively charged center that repelled positively charged alpha particles
  • center of the atom is the ‘nucleus’
  • the nucleus is tiny compared to the rest of the atom
  • the nuclear model/planetary model - 1920
23
Q

What are the limitations of Rutherford’s model?

A
  • an atomic nucleus composed entirely of positive charges should break apart as a result of electrostatic forces of repulsion
  • could not adequately explain the total mass of the atom (neutrons hadn’t been discovered yet)
  • accodring to scientific laws and understandings of the time an electron in motion around a central body must conticously emit radiation (as the electron loses energy it should sprial into obliterate the nucleus)
24
Q

What was James Chadwick experiment?

A
  • he bombarded beryllium with fast mocing alpha particles, a beam of particles was given off
  • the beam was not affected by magnest or charged objects. It must have been made of uncharged particles - neutrons
25
Q

What did Neils Bohr propose?

A
  • electrons exist in circular orbits with electrostatic force from the nucleus holding them in place
  • electrons can exist in only a series of allowed orbits (energy levels) that can hold a certain number of electrons. Therefore the energy of electrons are quantized
  • while an electron is in one orbit it does not radiate energy
  • electrons can “jump” between energy evels by absorbing and emmitting photons (packets of energy) carrying an amount of energy that equals the difference in energy levels of electrons
26
Q

How many ways can an atom absorbe energy and become excited in one of two ways?

A

2

27
Q

What are the ways an atom can absorb energy and become excited in?

A
  1. atom can collide with a highly energit particle (e.g. electron) in an electric current passing through a gas)
  2. Atom can absorb a phton that has an amount of energy equal to the difference betweent he energy of the orbit it occupies and energy of a higher orbit
28
Q

How does the Atomic LIne (Emission) Spectrum exist?

A
  • electrons excited to higher enrgy levels emit light when they fall back down
  • when passed through a prism, the pattern of light emitted is shown to be unique for each element
29
Q

What colour has the most energy?

A

violet

30
Q

What colour was the least energy?

A

red

31
Q

What happens when it is a hot gas that goes through the prism?

A

you get mostly black with the colours involved visible

32
Q

What happens when the high density hot matter goes through cold gas?

A

the absorption spectrum is the entire rainbow with the involved colours blacked out.

33
Q

When is the absoprtion spectra produced?

A

when atoms absorbe energy

34
Q

What is the absorption spectra comprised of?

A

dark lines or gaps in the line spectrum

35
Q

When is the emission spectra produced?

A

when atoms release energy

36
Q

What does the emission spectra comprise?

A

coloured lines in the spectrum

37
Q

How can the emission spectra be helpful?

A

in figuring out the composition of certain matter and the type of photoms emitted is helpful in figuring out the kind of elements the substance is made of as each element radiates a different amount of energy and has a unique emission level

38
Q

How can the absorption spectra be used?

A

to figure out the ability of certain objects to retain heat and its absorption level and in figuring out the number os substances in the sample

39
Q

How are emission and absorption spectra used in the real world?

A
  • anywhere where there are coloured lights
  • fireworks
  • neon signs
  • street lights
40
Q

What is the modern atomic theory?

A
  • all matter is made up of tiny particles called atoms, which are made up of smaller subatomic particles: protons, neutrons and electrons
  • the atoms of one element cannot be converted into the atoms of any other element by a chemical reaction (doesn’t include nuclear reactions)
  • atoms of one element have the same properties which are different from other elements - different isotopes of an element have different numbers of neutrons and thus different masses.
  • atoms of different elements combine in specific proportions to form compounds
41
Q

although an atom is divisble, it is still the smallest particle of an element that has the properties and indentity of the element

A

Chemistry (17 decks)

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