RADIOACTIVITY

Question 1

What is radioactivity?

Answer 1

The process by which certain types of unstable matter (e.g., atoms) emit energy and/or subatomic particles

An unstable or radioactive atom occurs if these forces are unbalanced (e.g., an excess of protons or neutrons), the atom will attempt to achieve stability by releasing energy called radiation. This radiation can be in the form of particles, beams, or rays.

Question 2

Where does radioactivity originate from?

Answer 2

Radioactivity originates form the nucleus, not from the electron cloud.

Any atom which emits radiation is called a radionuclide

Question 3

Why does a radioactive atom release energy?

Answer 3

Upon the release of energy (radiation), the nucleus is changed to form a more stable nucleus. Since this release of energy involves changes to the number of neutrons, protons, and electrons, the respective atom will decay into a new element

Question 4

What is transmutation?

Answer 4

The process of forming a new element

Question 5

How are the weights of elements related to stability?

Answer 5

Among the lighter elements, stable isotopes have approximately the same number of protons and neutrons

Among the heavier elements, stability requires more neutrons than protons

As an elements gets heavier, the prevalence for an element to be naturally radioactive increases

Question 6

Define ionising radiation

Answer 6

any type of radiation that possesses sufficient energy to detach electrons from atoms or molecules (ionising them)

Examples: high energy alpha and beta, as well as gamma and x-rays are examples of ionising radiation

Question 7

Define non-ionising radiation

Answer 7

Forms of radiation of lower energy and does not result in the ionisation of atoms or molecules

Examples: those in the electromagnetic spectrum with longer wavelengths/lower frequencies: UV, visible, infrared, microwaves, and radio waves

Question 8

What are the 4 discovered types of radiation?

Answer 8

1. Gamma particles
2. Alpha particles
3. Beta particles
4. Positrons

Question 9

What are the 5 main types of radioactive decay?

Answer 9

1. Alpha emission
2. Beta emission
3. Positron emission
4. Gamma emission
5. Electron capture

Question 10

Define alpha emission

Answer 10

Occurs when a particle equal to a helium nucleus is emitted from the nucleus of a radioactive isotope, results in a ‘daughter’ nuclide (transmutation) and an alpha particle

A new element or daughter nuclide is formed (transmutation occurs) which has a mass number 4 units lower, and an atomic number 2 units lower than the parent nuclide

Alpha particles are a form of ionising radiation, have low penetration and are slow moving. They can remove electrons from atoms or molecules die to their positive charge

Question 11

Define beta emission

Answer 11

Occurs when a neutron is converted to a proton and an electron, and the electron is emitted from the nucleus of a radioactive isotope

Results in ‘daughter’ nuclide and an electron

A new element is formed (transmutation occurs) where the daughter nuclide formed has the same mass number, and atomic number one unit greater than the parent nuclide

Have moderate penetrating power

Question 12

Define positron emission

Answer 12

Occurs when a positron emission (‘positive electron’) is emitted from the nucleus of a radioactive isotope

Beta emission results in a ‘daughter’ nuclide and a positron

A new element is formed (transmutation occurs) where the daughter nuclide formed has the same mass number, and an atomic number 1 unit lower than the parent nuclide

It is another form of beta decay

Question 13

Define gamma emission

Answer 13

In pure gamma emission there is no change in either the atomic number of the mass of the element. Rather, a nucleus in a higher (excited) state emits gamma radiation as it returns to its ground (most stable) state

During gamma emission, a new element is not formed (transmutation does not occur)

Asterisks (or the letter m) are used to indicate the element is in an excited state

Gamma rays have high penetrating power

Note gamma emission often accompanies alpha and beta emission and pure gamma emission, where the only radiation is gamma (and transmutation doesn’t occur), is rare

Question 14

Define electron capture

Answer 14

In electron capture, an electron is captured by a nucleus reacting with a proton to form a neutron

A new element is formed (transmutation occurs) where the daughter nuclide formed has the same mass number, and an atomic number is 1 unit lower than the parent nuclide

The transmutation end result is the same as for positron emission

Question 15

What is the half life of a radioactive isotope

Answer 15

The time it takes for one half of a radioactive isotope to decay is called its half-life, t½

An isotopes half-life is a convenient measure of the concentration or mass of a radioactive substance over time

Decay is exponential

Question 16

How do you use ionising radiation in X-rays, CT/CAT/PET scans

Answer 16

To create an image, radioactive isotope is administered which becomes concentrated in the targeted tissue

Radioisotope is detected and the intensity and location recorded

A computer is used to transform the intensity location data from the detector into a useful image

Question 17

What is a transuranic element?

Answer 17

Elements beyond uranium in the periodic table (atomic number greater than 92)

Do not occur naturally

To prepare these elements, heavy nuclei are bombarded with lighter ones

They are unstable and have very short half-lives; that of lawrencium-257, for example is only 0.65 seconds

Question 18

What is nuclear fusion?

Answer 18

the process of joining atomic nuclei to form a new, heavier nucleus