Radiation and Nuclear Stability Flashcards
What is the structure of an atom?
Dense nucleus: +vely charge protons and neutral neutrons
Surrounded by -vely charged electron cloud (very little mass)
What do mass number and atomic number define?
Mass number: P + n
Atomic number: e and P (same amount)
What is the atomic structure of uranium?
Isotopes: U-238 and U-235
92e-
number of neutrons much greater than number of protons.
When is a nucleus stable?
If the attractive forces holding the nucleus together balance or outweigh the repulsive forces acting to force the nucleus apart = stability.
When is a nucleus unstable?
If the repulsive forces acting to force the nucleus apart outweigh the attractive forces holding the nucleus together then the nucleus loses stability.
Nucleus spontaneous disintegrates, will emit particles and EM radiation = radioactive.
What is nuclear stability quantified by?
Nuclear binding energy
What is nuclear binding energy?
The energy required to split a nucleus into its component protons and neutrons.
Generally, >83 protons means nucleus is unstable (band of stability).
Nuclei of light elements less stable than heavier elements up to mass number of 56.
Nuclei of heavier elements less stable than elements that have a mass number of 56.
Definition of radioactivity
The spontaneous emission of energy and particles by atoms of certain elements producing new elements.
Definition of ionising radiation?
Has enough energy to to ionise atoms or molecules (eject e- from an atom)
What are the 7 types of ionising radiation?
Alpha decay Beta decay Gamma rays Positron emission Electron capture Proton emission Neutron emission
Describe alpha decay
Nucleus emits high speed doubly charged helium nuclei He(4 2)2+ (alpha).
Cause an atom to lose 2 protons and 2 neutrons.
Mass no will decrease by 4, atomic no will decrease by 2.
Describe beta decay
Nucleus emits high speed electron - e(0 -1)-
n -> P + e-
Associated with neutron decay:
- Decreases number of neutrons by 1
- Increases number of protons by 1
Atomic number increases by 1, mass number remains the same.
Describe gamma rays
- EM radiation
- Short wavelength, high energy
- No change in atomic mass or atomic number as gamma rays are photons of light.
Describe positron emission
Nucleus emits a particle similar to an electron, but has a positive charge - e(0 +1)
P -> n + e(+1)
Converting a proton to a neutron
- Protons decrease by 1, neutrons increase by 1
- Atomic mass remains the same
- Atomic number decreases by 1
Describe electron capture
Nucleus captures and electron.
P + e- -> n
Converting a proton to a neutron
