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PHYS852: Radiation Physics > Structure of Matter > Flashcards

Structure of Matter Flashcards

(57 cards)

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1
Q

What is a compound?

A

A group of chemical elements that can be decomposed into simpler substances.

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2
Q

What is an element?

A

Something that cannot be further decomposed by ordinary chemical means.

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3
Q

What is an atom?

A

The smallest quantity of a substance that can exist. Each species of atom is an element.

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4
Q

What is a molecule?

A

The smallest chemical unit of a substance capable of independent existence.

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5
Q

What is the charge of a proton?

A
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6
Q

What is the charge of a neutron?

A

0 C

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7
Q

What is the charge of an electron?

A
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8
Q

Define atomic number

A

The number of electrons or the number of protons.

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9
Q

Give the symbol for atomic number

A

Z

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10
Q

Define neutron number

A

The number of neutrons in a nucleus.

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11
Q

Give the symbol for neutron number

A

N

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12
Q

Define mass number

A

The number of nucleons (protons and neutrons).

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13
Q

Give the symbol for mass number

A

A

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14
Q

How can atoms be ionised?

A

1) By ionising one or more electrons (positive ion).
2) By gaining additional electrons (negative ion).

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15
Q

Define isotope

A

An atom with the same atomic number (Z) but a different number of neutrons (N).

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16
Q

Define isotone

A

Nuclides with the same number of neutrons (N) but a different atomic number (Z).

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17
Q

Define isobar

A

Nuclides with the same mass number (A).

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18
Q

What are the 2 units of energy?

A

SI unit: Joules (J)
Atomic unit: Electron volts (eV)

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19
Q

How are electron volts and joules related?

A
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20
Q

Give the equation that relates mass and energy

A
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21
Q

What is the mass-equivalence of an electron?

A

511 keV

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22
Q

What is the mass-equivalence of a proton?

A

938.27 MeV

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23
Q

What is the mass-equivalence of a neutron?

24
Q

What are atomic mass units?

Study These Flashcards
A

A unit used to express atomic or molecular weights.

25
What are Angstroms?
A unit used to express atomic or molecular distances. 1 Å = 0.1 nm
26
What are barns?
A unit of area, b, that measures the probability that a nuclear reaction will take place. A barn is a probability so isn’t equivalent to the physical cross-section of an atom.
27
What is a mole?
A measurement of the amount of any substance.
28
Define Avogadro’s number
The number of molecules in 1 mole of any substance.
29
Give the equation for the mass of 1 molecule of a substance
M = molecular weight N_A = Avogadro’s number
30
How many atoms per kg are in an element with an atomic mass, A?
N_A = Avogadro’s number
31
Give the equation for the mean volume occupied by one atom
V = volume A = mass number ρ = density N_A = Avogadro’s number
32
What are the 3 postulates of the Bohr model?
1) Electrons orbit the nucleus in stationary states. 2) An atom only emits/absorbs radiation when electrons transition between states. 3) Only certain stationary states are allowed. They have a quantised orbital angular momentum.
33
Give the equation for orbital angular momentum
L = nh / 2π L = angular momentum n = integer ≥ 1 h = Planck’s constant
34
Give the equation for de Broglie wavelength
λ = wavelength h = Planck’s constant p = momentum r = orbital radius
35
Give the equation for the orbital radius of an atom
r = orbital radius n = quantum number ε_0 = permittivity of free space h = Planck’s constant m = mass of the electron e = electron charge a_0 = Bohr radius
36
What is the Bohr radius?
The radius of the innermost (n=1) orbit of the hydrogen atom. It is equal to 0.0529 nm.
37
Give the equation for the total energy of an allowed orbit
E = total energy = PE + KE Term 1 = potential energy Term 2 = kinetic energy Term 3 = binding energy
38
Define binding energy
The energy required to remove an electron from its orbit.
39
Give the equation for the allowed states of an atom
E = energy n = quantum number E_1 = ground state energy
40
Define quantum number
The integer value, n, that determines the allowed orbital radii and total energies of a stationary state.
41
What are energy levels?
The allowed total energies for each stationary state of an atom.
42
What happens when an electron transitions between states?
A photon is absorbed or emitted.
43
Give the equation for the energy of photons absorbed/emitted by electron transitions
E_ph = photon energy h = Planck’s constant v = frequency E_f = final state energy E_i = initial state energy
44
What are characteristic energies?
The energies of photons emitted due to transitions of electrons between energy levels. The highest energy transitions generate characteristic X-rays.
45
What is the difference between an X-ray and a gamma ray?
An X-ray is produced due to electron excitation. A gamma ray is produced due to proton/nuclear excitation.
46
Give the equation that relates nuclear radius to mass number
r = radius r_0 = 1.2 fm A = mass number
47
Give the equation for the volume of a nucleus
r = radius
48
How are nuclear volume and mass number related?
Nuclear volume is proportional to mass number
49
The density of nuclear matter is approximately ________.
Constant
50
Give the equation for nuclear binding energy
B = binding energy Z = atomic number N = neutron number m = mass c = speed of light
51
Describe the graph of binding energy per nucleon against mass number
52
What are magic numbers?
The stable values of binding energy per nucleon for elements with a closed outer shell.
53
What are Q values?
The energy change in any transformation process (such as radioactive decay).
54
Give the equation for Q values
Q = Q value m_i = initial mass m_f = final mass c = speed of light
55
Define strong nuclear force
A short ranged, charge independent force that attracts nucleons towards one another at greater distances and repels them at very close distances, maintaining equilibrium.
56
Define Coulomb force
A long-ranged electric force that repulses subatomic particles with the same sign of charge.
57
The Coulomb force is about 50 times ______ than the strong nuclear force.
Weaker

PHYS852: Radiation Physics (13 decks)

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