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A-level Physics- Fields, particles and frontiers > The Nuclear Atom > Flashcards

The Nuclear Atom Flashcards

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1
Q

What was the Plumb pudding model?

A

A model that proposed the atom was a uniform mass of positive charge (the dough) dotted with negative charge (the dried fruit).

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2
Q

Describe the Rutherford experiment?

A

Scientist fired a beam of alpha radiation towards a sheet of gold leaf in a vacuum. They had a crystal of zinc sulfide and every time the zinc sulfide gave out a flash of light they could count and record where the alpha particles were going.

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3
Q

What were the two main observations made about the Rutherford experiment?

A

1) Most of the alpha particles went straight through the gold foil.
2) Some of the alpha particles were scattered through large angles.

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4
Q

What were the two main conclusions made about the Rutherford experiment?

A

1) The gold atoms were mostly empty space (vacuum)
2) Each gold atom has a positive nucleus with a radius less than about 10^-14m (A modern approximation for the radius of the nucleus is about 10^-15).

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5
Q

What is an alpha particle?

A

It is a helium nucleus with a charge of +2e, where e is the elementary charge.

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6
Q

What is the charge on a gold nucleus?

A

+79e

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7
Q

How can we calculate the force on a particle?

A

F = Qq/4π ε0r^2

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8
Q

What would have happened if the plum pudding model was correct?

A

Most of the alpha particles would’ve been stopped by the gold leaf but instead, most of the particles traveled straight through the gold leaf.

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9
Q

What did the plum pudding model results prove?

A

That there is lots of free space inside the atom if the alpha particles were traveling straight through.

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10
Q

What did they find once the alpha particles had been fired at the gold leaf?

A

They tended to deflect.

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11
Q

What did they gather due to the fact the alpha particles tended to deflect back?

A

That there must be a positive nucleaus due to an electrostatic repulsive force when a positive particle comes near to a positve nucleus it rebounds.

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12
Q

What did they conclude from the alpha particle scattering experiement? (2)

A

1) The atom was mostly an empty space.

2) There is a dense positive nucleaus.

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13
Q

What did they find in the later years and why?

A

That there was neutrons in the nucleaus too because the positive protons could not account for the mass of the elements.

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14
Q

How many alpha particles were defpected by the gold leaf?

A

About 1/2000

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15
Q

How many alpha particles were deflected through angles of more than 90 degrees?

A

About 1/1000

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16
Q

What force caused the deflection of alpha particles?

A

The Coulomb force.

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17
Q

What is the equation for the total energy at a point?

A

Et= Ek + Ep.

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18
Q

What is inside the nucleus of an atom?

A

Protons and neutrons.

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19
Q

When reading elements from the periodic table what are the number on the bottom and its given symbol?

A

Z = Proton number or Atomic number.

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20
Q

When reading elements from the periodic table what are the number on the top and its given symbol?

A

A = Nucleon number.

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21
Q

What is an isotope?

A

An element that has a different number of neutrons but the same number of protons.

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22
Q

Name 2 isotopes?

A

1) Tritium is an isotope of hydrogen with the Nucleon number being 3 instead of the normal hydrogen element which has 1.
2) Deuterium is an isotope of hydrogen with the Nucleon number being 2 instead of the normal hydrogen element which has 1.

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23
Q

What distinguishes what type of element something is?

A

The number of protons.

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24
Q

What does alpha radiation consist of?

A

Helium-4

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25
Q

What charge do neutrons have?

A

0

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26
Q

The number of electrons is the same number of?

A

Protons

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27
Q

The number of neutrons is given by?

A

A-Z, where A is the nucleon number and Z is the Protons number

28
Q

What is the rest mass of a proton?

A

1.673x10^-27kg

29
Q

What is the rest mass of a neutron?

A

1.675x10^-27kg

30
Q

What is the rest mass of an electron?

A

9.11x10^-31kg

31
Q

What is the Atomic mass unit symbol and value?

A

u=1.661x10^-27kg

32
Q

What is the atomic mass of a proton?

A

1u

33
Q

What is the atomic mass of a neutron?

A

1u

34
Q

What is the atomic mass of an electron?

A

1/2000u

35
Q

What is the diameter of a nucleus?

A

10^-15m

36
Q

What is the diameter of the atom?

A

10^-10m

37
Q

What is the equation for the radius of a nucleus?

A

R = r0A^1/3 where A is the nucleaon number and r0 is 1.2x10^-15.

38
Q

What is 1u defined as?

A

1/12 the mass of a carbon-12 atom.

39
Q

How many times smaller is the volume of a nucleus to the volume of the atom?

A

The volume of the nucleus is x10^15 smaller than the volume of the atom.

40
Q

What is the density of nuclear matter?

A

The density of nuclear matter is about 10^17kgm^-3

41
Q

What is happening when electrons are circling the nucleus of an atom?

A

The electron is being attracted inwards moving with circular motion due to the force being 90 degrees with its velcoity, it’s direction is only changing not it’s velocity and that’s why electrons don’t go into the nucleus itself.

42
Q

Why is a proton able to sit next to another proton?

A

Because of the strong nuclear force that acts over a very short distance and if you place the two positive particles close enough together the strong nuclear force will allow the two particles to exist next to each other.

43
Q

What is the repulsive force felt by two positive charges?

A

An electromagnetic force (electrostatic force).

44
Q

The shorter the distance between the two positive charges?

A

The greater the electromagnetic force.

45
Q

What carries the strong nuclear force between all nucleons in the nucleus?

A

A boson.

46
Q

What is a bosons half-life like?

A

Very short.

47
Q

Even if a boson was traveling close to the speed of light what could it still only do?

A

Can only transfer that force over a very short distance.

48
Q

What happens when two positive charges are very close to each other?

A

They feel a repulsive force.

49
Q

In the nucleus what is the strong force equal to?

A

The electrostatic force repulsive force.

50
Q

The heavier the element…?

A

The more unstable and therefore more radioactive and therefore don’t exist for a very long time because a boson can’t travel around the whole element holding it all together.

51
Q

What does the strong nuclear force act on?

A

Protons and neutrons.

52
Q

Sketch a graph showing how the nuclear force F varies with the separation r for two nucleons?

A

Look at answer page 210 texbook.

53
Q

Name 3 properties of the strong nuclear force.

A

1) It is repulsive at very short distances (<0.5fm)
2) It is attractive for r>0.5fm
3) It is attractive up to 0.3fm

54
Q

Name the 4 fundamental forces in order starting with the strongest to weakest.

A

1) Strong nuclear force
2) Electromagnetic force
3) Weak nuclear force
4) Gravity

55
Q

What do the strong nuclear and weak nuclear have in common?

A

They have a very shot range.

56
Q

What do electromagnetic and gravitational forces have in common?

A

They can act over infinite ranges.

57
Q

Define the Plum-pudding model.

A

A disproved theoretical model of the atom in which the neagtive charges were embedded in a uniform volume of positive charge.

58
Q

Define the proton number.

A

How many protons are in a nucleaus. Also called the atomic number. For atom X, the proton number is labelled at psoition Z: where A is the top number of X and Z is the bottom number.

59
Q

Define the nucleon number.

A

The total number of nucleons (protons + neutrons) in a nucleaus. For atom X, the proton number is labelled at position A: where A is the top number of X and Z is the bottom number.

60
Q

Define an isotope.

A

Nuclei of the same element that have the same proton number, but different nucleon numbers. The different nucleon numbers are caused by the different number of neutrons in each nucleus.

61
Q

Define Atomic mass.

A

1u=1.661x10^-27kg. 1u is one-12th the mass of a carbon-12 atom.

62
Q

Define the Strong nuclear force.

A

One of the fundamental forces. Holds the nucleus of an atom together. Repulsive below 0.5fm, and attractive between 0.5fm and 3fm.

63
Q

What do protons within a nucleus experience?

A

Large electrostatic repulsive forces.

64
Q

What is too small to explain why the protons remain in the nucleus?

A

The attractive gravitational force between the protons.

65
Q

What do all nucleons in the nucleus experience?

A

The strong nuclear force.

A-level Physics- Fields, particles and frontiers (1 decks)

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