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Chem > Chem test #2 > Flashcards

Chem test #2 Flashcards

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1
Q

What were Democritus’ two earliest ideas about the atom?

A
  1. Atoms can not be cut (indivisible)
  2. An atom is the smallest particle of an element that retains the chemical identity of that element
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2
Q

What are the five main points in Dalton’s atomic theory?

A
  1. Matter is composed of tiny particles called atoms
  2. Atoms are indivisible and idestructable. In a reaction, they are combined or rearranged but never broken apart (later disproved)
  3. Atoms of a given element are identical in size, mass, and chemical properties (later disproved)
  4. Atoms of one element are different from those of another element
  5. Different atoms combine in simple, whole number ratios to form compounds.

Dalton is responsible for the billiard ball model of the atom.

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3
Q

How did J.J. Thompson contribute to the development of modern atomic theory?

A

Cathode Ray Tube experiment -
Experiment: Add an electric field and measure the deflection of particles
Conclusion: The negatively charged particles are electrons and atoms are not indivisible

Plum Pudding Model of the Atom:
- Showed that negatively charged electrons are embedded in a core of positive charge
- Overall, atoms have no charge

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4
Q

How did Robert Andrews Milikan contribute to the development of modern atomic theory?

A

The Oil Drop Experiment:
- Conclusion: The charge of an electron
e- = 1.6 x 10^-19 coulombs

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5
Q

How did Ernest Rutherford contribute to the development of modern atomic theory?

A

The Gold Foil Experiment:
Experiment - send alpha particles through a piece of gold foil inside a flourescent screen
Result - Some alpha particles passed straight through the foil while others deflected.
Conclusion - The atom is mostly empty space. There must be a dense area of positive charge inside an atom. The small, dense, positive area is known as the nucleus.

Rutherford’s model of the atom:
- Showed that atoms have a small, dense nucleus of positive charge
- Showed that negatively charged electrons exist around the nucleus

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6
Q

What is an atom?

A

The smallest form of matter retains the element’s properties

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7
Q

What is the nucleus?

A

Small, positively charged, dense center of an atom; contains protons and neutrons

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8
Q

What is a proton?

A

Symbol: p+
Where are they located: The nucleus
Relative charge: 1
Mass: 1 amu (1.673 x 10^-24)

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9
Q

What is a neutron?

A

Symbol: n0
Where are they located: The nucleus
Relative charge: 0
Mass: 1 amu (1.675 x 10^-24)

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10
Q

What is an electron?

A

Symbol: e-
Where are they located: In the space around the nucleus
Relative charge : 1-
Mass: 1/840 amu (9.11 x 10^-28)

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11
Q

What is an atom’s atomic number?

A

The number of protons in an atom; determines the identity of an element

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12
Q

What is an atom’s mass number?

A

The total number of protons and neutrons in the nucleus, whole #

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13
Q

What are isotopes?

A

Atoms of the same element with the same number of protons and a different number of neutrons

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14
Q

What is an atom’s atomic mass?

A

The weighted average mass of the isotopes of an element

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15
Q

What is radioactivity?

A

The spontaneous emission of particles from an atom’s nucleus

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16
Q

What is the different between an element being stable or unstable?

A

Stable - Nucleus stays together, good proton to neutron ratio

Unstable - Nucleus breaks down and emits radiation, not ideal proton to neutron ratio

17
Q

What is radioactive decay?

A
  • Unstable nuclei emit particles in order to become stable
    -Decay continues until a stable proton to neutron ratio is achieved
  • There are different types of decay that can occur
18
Q

What is an alpha particle?

A

Mass (amu): 4 amu
Charge: 2+
Penetrating power: paper
Composition : 4 HE 2+
2

19
Q

What is a beta particle?

A

Mass: No mass
Charge: 1-
Penetrating power: Aluminum
Composition: 0 e -
-1

20
Q

What is a gamma particle?

A

Mass: No mass
Charge: No charge
Penetrating power: Lead
Composition: Photons

21
Q

Main difference between alpha particles, beta particles, and gamma particles

A

Beta: 1- charge
Gamma: No charge
Alpha: 2+ charge

22
Q

What is a nuclear reaction (transmutation)?

A

Any reaction that involves a change to an atom’s nucleus?

23
Q

What’s the difference between a nuclear reaction and a chemical reaction?

A

Chemical - Elements are combined or rearranged but their identity stays the same

Nuclear - Elements are formed (does not obey law of conservation of matter)

24
Q

What is a half life?

A
  • The time it takes for a radioactive sample to decay by 1/2
  • Constant for a particular element
  • Unique for different elements (ranges from fractions of seconds to billions of years)
  • Counteracted by fusion in the starts as well as decay of larger species and synthesis in the lab
25
Q

What is induced transmutation?

A

The process of striking the nucleus of an atom with a high velocity particle to begin the nuclear reaction

26
Q

What is fission?

A
  • One large atom breaks apart into 2 smaller atoms
  • Mass of the products is slightly less than the mass of the reactants
  • E = mc2
  • Neutrons produced feed chain reaction
27
Q

What is a chain reaction?

A

Neutrons released during a fission reaction go on to hit additional nuclei and induce more fission reactions

28
Q

What is fusion?

A
  • Two smallers atoms combine to form 1 larger atom
  • Releases a lot of energy
  • How heavier elements are formed
29
Q

What is a thermonuclear reaction?

A

A nuclear fusion reaction that requires an enormous amount of heat to start

30
Q

What are some practical uses of nuclear reactions?

A

PET scans: Scan used to detect cancer and thyroid function

Radiation treatment: High energy readiation used to shrink cancer cells

Radioisotope dating: Helps determine how old fossils are

31
Q

How does a nuclear reactor produce electrical power?

A
  1. Enriched uranium fuel rods undergo a fission reaction
  2. The fission reaction produces a lot of thermal energy (heat)
  3. Heat is used to turn water into steam
  4. Steam then turns a turbine
  5. The turning turbine creates friction to create a stream of electrons (electricity)
  6. Electric current feeds into power grid
32
Q

What are safety considerations in a nuclear power plant?

A
  • Low levels of radiation even during normal operation
  • Domestic and international terrorism (soft target)
  • Leaks and contamination to the surrounding area
  • Regulations/limits on nuclear power
33
Q

What are the pros and cons of nuclear power in terms of its affect on the environment?

A

Pros: Does not produce CO2 or methane, much more energy efficient than any other power source

Cons: Produces radoactive wastes, not renewable

Chem (5 decks)

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