Atomic and Nuclear Structure

Question 1

Which of the decay process is due to a deficit of neutrons?

• Internal conversion
• Electron capture
• Alpha particles
• Beta -

Answer 1

Electron capture

Electron capture decay is a result of a deficit of neutrons (low neutron to proton n/p ratio).

Question 2

How does the low neutron to proton ratio increase?

Answer 2

Via electron capture by the nucleus to transform proton to neutron, often called K capture

Question 3

What are the two decay processes that produce emission of Auger electrons?

Answer 3

• Internal conversion
• Electron capture

Question 4

Define Beta minus decay

Answer 4

In beta minus (β−) decay, a neutron is converted to a proton, and the process creates an electron and an electron antineutrino; while in beta plus (β+) decay, a proton is converted to a neutron and the process creates a positron and an electron neutrino. β+ decay is also known as positron emission.

Question 5

Define Auger electron emission

Answer 5

a vacancy in an inner shell is filled by an electron in an outer shell, and another outer shell electron is ejected from the atom by the result of the characteristic X-ray being admitted by an electron filling the lower shell vacancy.

Question 6

As part of the Auger electron emission/process an electron in the K shell is vacant and filled by an electron from L shell, as a result what is being emitted?

Answer 6

K shell characteristic X-ray

Question 7

What is another name for gamma ray emission?

Answer 7

Nuclear de-excitation

Question 8

What is internal conversion?

Answer 8

The nucleus transferring its excess energy directly to the atomic electron which is then ejected from the atom.

Usually the ejected electron is a K shell electron though L&M shell electrons can be ejected as well with lower probability. These electrons have discrete energies and the emitted electron results in either

Fluorescence or characteristic x-rays or Auger electron emission

Question 9

What is fluorescence or characteristic x-rays?

Answer 9

Electrons cascade “down” to lower-energy unoccupied shells emitting x-rays with well defined discrete energies

Question 10

What is Auger electron emission?

Answer 10

A vacancy in an inner shells is filled by an electron in an outer shell, and another outer shell electron is ejected from the atom

Question 11

What is isomeric transition?

Answer 11

When the nucleus retains its stored energy and becomes “metastable” and is the state that 99mTc exists in before it releases a gamma ray and becomes 99Tc.

Question 12

The ratio of neutron / proton increases with

Answer 12

Z (atomic number)

Question 13

Element with more than Z > 83 is considered

Answer 13

unstable

Question 14

The mass of a nucleus is always less than the rest mass of that nucleus, why?

Answer 14

Binding energy

Question 15

What are the two ways to extract energy via nuclear decay?

Answer 15

1. Fission
2. Fusion

Question 16

Give an example of fission

Answer 16

235 Uranium fission

235U + neutron –> 236U –> 141Ba + 92Kr + 3n + energy

Question 17

Give an example of fusion

Answer 17

fusion of the low Z nuclei

2H + 2H –> 2He + n + energy (3.27 Mev)

2H: deuterium (hydrogen + neutron)

Question 18

Beta - (minus) decay occurs in

Answer 18

neutron-rich nuclei

Question 19

Describe electron caputre.

Answer 19

In electron capture, an inner-shell electron interacts with the nucleus and the result is that a proton is lost.

As a result, a neutron is made.

Question 20

Example of the electron capture?

Answer 20

125 Iodine decaying into 125mT (Tellurium) in a metastable state

Question 21

As a result of the electron capture what is being produced?

Answer 21

After electron capture, there is a vacancy in an inner shell electron and an outer shell electron can transition into this state, producing a characteristic photon.

Auger electron can also be emitted.