Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Foundation Class > Atomic Structure > Flashcards

Atomic Structure Flashcards

1
Q

Describe Protons

A

Located in nucleus
Positive 1 charge (+1)
Mass=1.007277 amu (located in chart of nuclides)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Describe Neutrons

A

Located in nucleus
Neutral charge
Mass=1.08665 amu (located in chart of nuclides)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Describe electrons

A

Orbit the nucleus
Negative 1 charge (-1)
Mass=0.0005486 amu (located in chart of nuclides)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Define Nuclide

A

Atoms with varying combinations of protons and neutrons. (This encompasses all atoms, about 2500 nuclides have been identified)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Define Isotope

A

Atoms of same element (same number of protons, Z) with varying number of neutrons (N). Variants cause the Atomic Mass Number (A, total number of nucleons) to vary.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Define Atomic Number (Z)

A

Total number of protons in an atom.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Define Mass Number (A)

A

Total number of nucleons in a atom.
A=Protons+Neutrons.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What are the 3 forces acting on a nucleus?

A

Gravitational force
Electrostatic force
Nuclear force

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Describe gravitational force in atoms

A

Weak force between nucleons withe a relatively LONG range.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Describe Electrostatic force in a nucleus.

A

Strong repulsive force between like charged particles (protons) with relatively LONG range.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Describe Nuclear force in nucleus of atoms

A

String attractive force between all nucleons with Extremely SHORT range.
(Holds nucleus together against Electrostatic force)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

How does an atoms Neutron/Proton ratio affect stability?

A

Smaller atoms have 1:1 ratio for stability. As atom gets larger, the number of neutrons gradually increases >1 per proton to achieve stability. Ex. U-238 has 92 protons and 146 neutrons for a neutron:proton ratio of 1.587.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Define Atom percent (a/o).

A

% of atoms of an element that are a particular isotope.
Ex. A cup of water has 8.23x10-24 atoms. If O-18 a/o is 0.20%, then there are 1.65x10-24 atoms of O-18 in the cup.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Define Atomic Weight.

A

Average atomic weight of all isotopes of the element.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Define Weight Percent (w/o)

A

% of weight of a particular isotope of an element.
Ex. Sample of U-235 contains 100 kg of uranium. If w/o of U-235 is 28 (28%), then 28 kg of U-235 is present in the sample.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What is Enriched Uranium?

A

Uranium with higher concentration of U-235 than natural Uranium.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

What is Depleted Uranium?

A

By-product of enrichment process.
U-235 concentration is lower than natural Uranium (.72%).

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

Define Mass Defect.

A

Mass of an atom is always slightly less than the sum of the nucleons and electrons.
Difference in mass between a formed atom and the sum of all its components.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

Define Binding Energy (BE)

A

A change in mass occurs from the conversion of mass to energy (BE) during formation of the nucleus. Amount of energy required to separate particles of a nucleus. Also amount released when nucleus is formed.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

Calculate mass defect (delta m)

A

Delta m=[Z(m(p)+m(e))+(A-Z)m(n)]-m(atom)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

Calculate Binding Energy (BE)

A

BE=delta m(931.5MeV/1 amu)
Units=MeV

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

Describe an x-ray and it’s production.

A

Emitted by excited electrons that transition to some lower energy state.
Equal to difference in energy level the electron transitions to. Longer wavelength than gammas.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

Describe Gammas and their production.

A

Excited nucleus transitions to lower energy state by emitting a gamma ray. Shorter wavelength than X-rays.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

What is Ionization?

A

Process of removing an electron from an atom.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

What is Ionization Energy?

A

Energy required to remove an electron from an atom.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

What is Conservation of Electric Charge?

A

Charges are neither created nor destroyed. Positives and negatives can neutralize each other. A neutron can produce positive or negative particle from different processes.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

What is Conservation of Mass Number?

A

Net number of nucleons remains the same. Can change from proton to neutron and vice versa.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
28
Q

What is Conservation of Mass and Energy?

A

Total kinetic energy and energy equivalent of the mass in a system must be conserved in all decays and reactions. Can convert mass to energy and vice versa. Sum of Mass and mass equivalent energy is constant.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
29
Q

What is Conservation of Momentum?

A

Total amount of momentum (distribution of kinetic energy among product nuclei, particles, and/or radiation) is the same before and after a reaction.
Can be distributed differently among entirely different nuclides and/or particles.

30
Q

Describe alpha decay

A

Emission of alpha particle (He nucleus) from an unstable nucleus. Atomic number lowers by 2 and Mass number lowers by 4.

31
Q

What is beta decay?

A

Emission of electrons from the nucleus rather than the electron cloud.

32
Q

What is beta minus decay?

A

Negative electron emitted from nucleus causes atom to be positively charged, as a result a neutron is converted to a proton because it lost a negative. An antineutrino and an electron are emitted.

33
Q

What is beta plus decay?

A

A positively charged electron (positron) emits from a nucleus creating a negatively charged nucleus. A proton converts to a neutron as a result. A Neutrino and a Positron are emitted.

34
Q

What is electron capture?

A

Nucleus of an atom absorbs an electron from inner orbit (k-shell) to combine with a proton to form a neutron. A neutrino is emitted.

35
Q

What is Gamma Emission?

A

Photon radiation emitted from the nucleus that have wave and particle properties.
High Penetrating type of radiation.
Needs several inches of metal or several feet of concrete to shield.

36
Q

What is Internal Conversion?

A

Gamma ray that interacts with innermost electrons of the atom. Energized electron is ejected with KE equal to the gamma energy minus the BE of the electron. Another electron drops to lower energy level to fill the hole and emits an X-ray.

37
Q

What is Isomeric Transition?

A

A nucleus that is excited differs in energy and behavior from other nuclei with identical atomic number/mass number. This transition happens when excited nucleus (isomer) drops to lower energy level, emitting gamma radiation and changing nucleons.

38
Q

What is Neutron Emission?

A

Non stable nuclei May also emit neutrons to become more stable.
Lots of KE. Small size and can penetrate many materials.

39
Q

Predict the type of decay based on nuclides position relative to the Line of Stability.

A

Below and to right-beta minus.
Above and to left-beta plus decay.
Upper right region-alpha decay.

40
Q

How to determine decay chain using chart of nuclides.

A

Chart indicates type of decay for a particular nuclide. Using rules for that decay, move along the chart until stable nuclide is attained.

41
Q

Describe Charged Particle Interaction.

A

Have electrical fields that interact with the atomic structure of material they are passing thru. This slows the particle while accelerating electrons (which then escape) of atoms they pass by.

42
Q

Describe Uncharged Particle Interaction.

A

No electric field. Interact by collisions or scattering.
Photons lose energy by PEE, Compton Scattering, or Pair Production.

43
Q

Describe Specific Ionization.

A

Number of ion pairs formed per centimeter of travel in a given material.
Caused by ionizing radiation.
# ions/cm

44
Q

Describe Alpha particle interactions.

A

From decay of heavy nuclides.
Hi positive charge causes electrons to strip from neighboring atoms to combine with the alpha. Energy is removed as electrons are stripped and Helium atom is result.

45
Q

Describe Beta Interaction.

A

Displaces electrons from orbit. Electron slows more after each collision until it is absorbed by an atom.

46
Q

Describe Positron Interaction.

A

Identical to beta minus particles but with positive charge. Interact similarly with matter as well.
Short lived and quickly annihilate w/negative electrons which produces 2 gamma rays equal to the mass of the electrons. Gammas then interact with matter.

47
Q

Describe Neutron Interactions.

A

From fission or decay. Difficult to stop with no charge and larger size than electron.
Hi penetrating power.
Attenuated by:
1: elastic Scatter
2: Inelastic Scatter
3: Absorption

48
Q

Describe Neutron Elastic Scatter

A

Neutron collides with another nucleus and transfers some or all of its Kinetic Energy to the nucleus. Net Kinetic Energy is conserved.
Neutron slows.

49
Q

Describe Neutron Inelastic Scatter

A

Neutron collides with another nucleus and not all kinetic energy is conserved. Some transfers to internal energy absorbed by the nucleus which becomes excited.
Neutron slows.
Excited nucleus can then emit a gamma ray which can also interact with matter.

50
Q

Describe Neutron Absorption

A

Neutron is absorbed in a nucleus of an atom which leaves it excited.
Can result in radioactive capture-resulting in gamma emission, or fission-atom splits into smaller atoms releasing neutrons and gammas.

51
Q

What are 3 types of gamma interactions?

A

Photoelectric Effect
Compton Scattering
Pair Production

52
Q

Describe Photoelectric Effect

A

Low energy gamma strikes orbital electron. ALL of the gamma’s energy is expended ejecting the electron from orbit resulting in ionization and a hi energy electron.
Rarely occurs w/gammas >1MeV.

53
Q

Describe Compton Scattering

A

Elastic collision between photon and electron. Photon has excess energy required to eject electron and retains some of its energy as it and the electron are scattered.
Atom is ionized. Hi energy beta and lower energy photon result.
From gammas between 1.0-2.0 MeV.

54
Q

Describe Pair Production

A

Hi energy gamma (photon) passes close enough to a HEAVY nucleus and it’s energy is transformed into both an electron and positron. Very little KE is transferred to the nucleus and mostly to the pair.
Gamma must have at least 1.02 MeV to start.

55
Q

How to shield Alpha Radiation.

A

Loses energy quick due to large mass and positive charge.
A few centimeters of air or;
A sheet of paper.

56
Q

How to shield Beta Particles.

A

More penetrating than alphas but still relatively easy to stop.
Thin layer of metal.
Also human skin.

57
Q

How to shield Neutron Radiation.

A

Difficult to stop w/Hi penetrating power.
Use material w/similar mass for elastic scattering.
Hydrogenous material-like water.
12” water is effective.

58
Q

How to shield Gamma Rays.

A

LEAD
No mass, no charge and hi penetrating power.
Heavy nuclei such as lead make large targets for gamma rays.
Several meters concrete or water, or a few inches of lead work.

59
Q

Define Radioactivity

A

Certain nuclides spontaneously emit particle or gamma radiation.
Individual radioactive emissions can’t be predicted, however,
Average behavior of large sample can be accurately determined w/statistics.

60
Q

Define Radioactive Decay Constant (lambda)

A

Probability per unit time that an atom of a specific nuclide will decay.
Units are ‘per’ unit time. (1/time)

61
Q

Define Activity (A)

A

Decay rate of a sample.
Number is disintegrations per second.
Takes into account total mass (number of atoms) of a sample.
A=lambda x N
Where:
A=activity
N=number of atoms

62
Q

Define Radioactive Half-Life.

A

The amount of time required for the activity to decrease to half of its original value.

63
Q

Define a Curie.

A

Rate of radioactive decay.
=3.7x10^10 disintegrations per second.

Equivalent to the number that 1 gram Radium-226 decays in 1 second.

64
Q

Define Becquerel.

A

Also rate of radioactive decay.

=1 disintegration per second.

By this note that 1 Ci=3.7x10^10 Becquerels.

65
Q

Equation for half life using decay constant.

A

t(1/2)=(0.693/lambda)

66
Q

An equation to find final activity when given initial activity, decay constant and half-life.

A

A=A(o)•e^[-lambda(t)]

67
Q

How many half lives does it take before the number of atoms left is negligible?

A

5 to 7

68
Q

Calculation for Activity (number of atoms present) over time.

A

Since A=A(o)•e^[-lambda(t)], and
A=lambda•N, therefore,
N=N(o)•e^[-lambda(t)].

Lambda cancels out.

69
Q

How to figure out Number of atoms

A

N=mass•(1 mole/isotopic mass)•(N(a)/1 mole).
N(a)=Avocado’s number.

70
Q

Define Radioactive Equilibrium

A

Nuclide decay and production rates are equal.
Number of atoms present remain the same over time.

71
Q

Define Secular Equilibrium.

A

Parent has extremely long half-life.
Each descendant in the decay chain is built up to equilibrium except the final stable element which constantly increases.
Equilibrium is established by the half-life of the original parent.

72
Q

Name of a RAD dude.

A

RAY!!!!!

Foundation Class (8 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions