Atomic structure and nuclear chemistry

Question 1

what is the atomic number

Answer 1

number of protons in the nucleus of an atom

Question 2

what is the mass number

Answer 2

sum of protons and neutrons in the nucleus

Question 3

what is an isotope

Answer 3

atoms with the same atomic number but different mass number (same number of protons, different number of neutrons

Question 4

what happens to stable isotopes

Answer 4

they remain unchanged indefinitely

Question 5

what happens to unstable isotopes

Answer 5

• undergoes spontaneous disintegration in order to become a stable nucleus
• disintegration results in emissions of small particles and/or radiation
• also called radioactive isotopes

Question 6

what does mass spectrometry measure

Answer 6

measures the molecular weight of atoms or compounds by observing the mass to charge ratio (m/z) of ions

• the position of the peaks identifies
• peak intensity gives relative abundance

Question 7

process of mass spec

Answer 7

• atoms and molecules are converted into ions, which can be separated on the basis of their masses and motions in magnetic or electrical fields
• works for both stable and unstable isotopes

Question 8

what happens during radioactive decay

Answer 8

during radioactive decay, the nucleus of an unstable radioisotope seeks energetic stability by emitting particles/radiation (alpha, beta, gamma photons)

Question 9

what is half-life of a radioactive isotope

Answer 9

the time taken for the activity of a given amount of a radioactive substance to decay to half of its initial value

Question 10

What is Alpha radiation?

Answer 10

• emission of an alpha particle
• helium nuclei
• positively charged

Question 11

What is Gamma rays?

Answer 11

• emissions of a gamma photon
• high frequency EM radiation
• neutral
• no effect on atomic or mass number
• often produced along with alpha or beta particles - a or B decay leaves the nucleus in an excited state and then it loses energy by gamma emission

Question 12

how to write the generic alpha decay equation

Answer 12

A/Z X = A-4/Z-2 X + 4/2a

radiation emitted = 4/2a

Question 13

what is alpha’s penetrating capability

Answer 13

paper

Question 14

what is Beta’s penetrating capability

Answer 14

aluminum

Question 15

what is Gamma’s penetrating capability

Answer 15

Lead

Question 16

where can unstable isotopes be used

Answer 16

INDUSTRY 
- energy generation 
sterilization of food and medical supplies (60Co)
- imaging and gauging 
DOMESTIC 
- smoke detectors using 241Am
MEDICAL 
- diagnostic
- therapeutic - weakening or destroying particular targeted cells

Question 17

what is required for unstable isotopes to be used in imaging
- give common examples

Answer 17

a radioisotope used for diagnosis must emit gamma rays of sufficient energy to escape from the body.
it must have a half-life short enough for it to decay away soon after the imaging is completed
EXAMPLES
- 99Tc - half-life = 6 hours, emits gamma and low beta particles
- myocardial perfusion imaging uses 20TICL, 82Rb, or 99Tc - it is for the detection and prognosis of coronary artery disease
- PET imaging often uses 18F-Fluoro-deoxyglucose (FDG) - half-life 110 minutes - measures cell metabolism