Radioactivity: The release of nuclear radiation in the form of particles and rays
from a radioactive element
Scientists to remember for their contributions:
 Henri Becquerel (1896): French scientist, Provided evidence of x-rays
and Uranium “nuclear radiation”
 Marie Curie (Polish): She and her husband (Pierre) discovered
radioactive elements and named them Polonium (after Poland) and
Radium (shining element). Coined the term “radioactivity”.
 Ernest Rutherford: Produced the first artificial transmutation (an element
changing into another), A particle accelerator uses magnets and electric
fields to speed up particles
What happens during radioactivity?
•Particles and rays are emitted when a radioactive element or isotope breaks
down.
•The reason they break down has to do with stability.
•All atoms want to be stable and sometimes radioactive ones aren’t resulting in
radioactive decay.
Nuclear Stability
•Binding energy is needed for the stability of a nucleus. The binding energy
keeps the nucleus together, it’s like glue
•High: stable
•Low: unstable
•Many elements have radioactive isotopes.
Ex. Carbon 12: nonradioactive (coal, diamond, graphite) Carbon 14: radioactive
(used for carbon dating)
* a nucleus that is unstable can become stable by undergoing a nuclear
reaction or change *
Radioactive Decay
•The spontaneous breakdown of an unstable atomic nucleus. The unstable
nucleus breaks apart.
•When it breaks apart it emits particles or rays to become lighter and become
more stable
DECAY SERIES
•The series of steps by which a radioactive nucleus decays into a non-radioactive
nucleus. The element goes from radioactive to non-radioactive.
Alpha Decay
•Occurs when a nucleus releases an alpha particle
•Alpha particles result from the decay of relatively heavy radioisotopes. They
consist of two neutrons and two protons, bound together (a Helium nucleus).
•Example: Americium is commonly found in household smoke detectors.
Alpha Particles
(made of 2 protons and 2 neutrons)
•Comes from the nucleus of a He (Helium) atom, It is the weakest type of particle
•Has a positive charge (+), Can burn flesh but is stopped by a sheet of paper
Beta Decay
•Loses a beta particle (an electron) and the # of protons increases by 1, In beta
decay, a neutron converts (changes) to a proton emitting a beta particle
(electron) in the process. The beta particle is identical to an ordinary electron.
•Example: Carbon-14 (C-14) is a radioisotope of carbon, which undergoes beta
decay and may be familiar for its use to establish the age of ancient artifacts
("carbon dating").
•Remember isotopes are when you have more neutrons than protons
Transmutation: Where one element changes into another as a result of
changes in the nucleus (beta decay).
Beta Particles (the same as an electron)
•An electron is formed in the nucleus of an atom when a neutron breaks apart, It
is 10x stronger than an alpha particle, It can pass through 3 mm of solid
aluminum
Gamma Decay
•Release of a gamma ray
•The nucleus is not changed only lowered to a different energy level
•Gamma rays are emitted (released) if a nucleus still has more energy after
decay. The energy is electromagnetic in nature and has a unique energy.
•Gamma rays are not physical particles, but their interactions with matter are
described by assigning them particle-like properties.
Gamma Rays (Actually a burst of high frequency waves)
•An electromagnetic wave of high frequency and short wave length, Strongest
type, very harmful, Can pass through several cm of solid lead
Radioactive Half-Life
•The halflife is the amount of time it takes for half of the atoms in a sample to
decay.
•The halflife for a given isotope is always the same ; it doesn't depend on how
many atoms you have or on how long they've been sitting around.
The halflife is always the same, but the half (the sample) gets smaller and
smaller.
Nuclear Fission: Splitting of an atomic nucleus into 2 smaller nuclei of
approximately equal mass. A nucleus breaks into 2 pieces.
“I BREAK” “I break a nucleus in 2”
Nuclear Fusion
•Joining of 2 atomic nuclei of smaller mass to form a single nucleus of a larger
mass.
•Temperature must be well over a million degrees Celsius
•Fusion produces less radioactive waste
–Ex: the sun & atomic bombs
“U MAKE” “you make a nucleus”
Radioisotopes and tracers
Used for detecting chemical leaks, diagnosing disease, Killing cancers cells
Effects: Can actually cause the very disease that it fights, Can damage DNA
Devices that detect radioactivity:
•Cloud Chambers: detects alpha and beta particle radiation, leaves a trail of ions
in the water or ethanol vapor (gas) in the chamber
•Bubble Chamber: detects alpha and beta particle radiation, holds a superheated
liquid in which particles leave a path of bubbles if they are present
•Electroscopes: Has leaves that repel or attract each other depending on the
charge in the air
•Geiger Counter: measures radioactivity by producing an electric current when
radiation is present, detects alpha, beta and gamma radiation
Radiation Sickness Symptoms:
1. Nausea
2. Fatigue
3. Loss of hair
4. Can cause death