Radioactivity

Question 1

What is radioactivity?

Answer 1

Material that contains unstable nuclei so will spontaneously lose energy by radiation

Question 2

What makes an atom unstable?

Answer 2

Incorrect balance of protons and neutrons

Isotope: same number of protons but different number of neutrons (some are stable, some are not)

Unstable isotopes: radioisotopes (disintegrate to a lower energy state)

Naming isotopes: put the mass number next to the element name eg. Carbon-12, carbon-14

Question 3

What is the valley of stability?

Answer 3

=indicates those atoms that are stable

For atoms with fewer protons you need the same number of protons as neutrons for stability

As number of protons increases you need more neutrons than protons for stability

Question 4

What are the 5 radioactive decay processes?

Answer 4

Alpha emission: emission of alpha particles with KE

Beta emission: emission of beta negative particles + KE

Positron emission: emission of beta positive particles + KE

Electron capture: no particles emitted; followed by gamma emission

Gamma emission: emission of gamma photons of EMR, immediately follows decay process in some radionuclides

Question 5

what is alpha decay?

Answer 5

emission of helium nucleus (2 neutrons, 2 protons)

Question 6

what is beta decay?

Answer 6

emission of electron or positron

Question 7

How does a neutron become a proton?

Answer 7

Neutron to proton= beta decay (a neutron (made of one up quark and two down quarks) can transform into a proton (made of two up quarks and one down quark), an electron, and an electron antineutrino)

Question 8

what is positron emission?

Answer 8

Flourine-18 decays to oxygen-18 in T1/2 109 mins and this emits a positron which when combined with fludeoxyglucose will travel to areas of high metabolism e.g. tumors

Question 9

What is electron capture?

Answer 9

nucleus captures one of the orbiting electrons resulting the proton being transformed into a neutron

Question 10

What is gamma decay?

Answer 10

occurs when nucleus is in an excited state eg. pure gamma emission, electron capture, internal conversion, gamma ray emission

Question 11

What is the decay chain?

Answer 11

a nuclide may undergo several decays before it becomes stable. eg. uranium (parent) has 14 decays to form stable lead (daughter)

Question 12

What is activity?

Answer 12

The rate of decay. Number of disintegrations per second.
eg. 1 Bq = 1 disintegration/ second
1 curie= 3.7 x 10^10 disintegrations/second (1mCi=37MBq)