Post on 30-Dec-2015
Sc Standards PS 2.2
Illustrate the fact that the atoms of elements exist as stable or unstable isotopes.
Universal ForcesUniversal Forces
Gravitational Force-Gravitational Force- Force of attraction between two masses.Force of attraction between two masses.
Electro-magnetic Force-Electro-magnetic Force- Force of attraction between two opposite charges Force of attraction between two opposite charges
(force of repulsion between two like charges).(force of repulsion between two like charges). Weak Nuclear Force-Weak Nuclear Force-
A force found within the nucleus which is responsible A force found within the nucleus which is responsible for certain types of nuclear decay.for certain types of nuclear decay.
Strong Nuclear Force-Strong Nuclear Force- A force found within the nucleus which helps hold the A force found within the nucleus which helps hold the
nucleus together. (The glue that keeps the protons nucleus together. (The glue that keeps the protons and neutrons close together.)and neutrons close together.)
RadiationRadiation
Think back to the egg lab. What Think back to the egg lab. What would happen if there were too would happen if there were too many protons and neutrons to fit many protons and neutrons to fit in the egg?in the egg?
RadiationRadiation
Particles and Energy emitted from Particles and Energy emitted from the breakdown of the the breakdown of the nucleusnucleus of an of an atom.atom.
History LessonHistory Lesson
Henri Becquerel (1852 Henri Becquerel (1852 - 1908)- 1908)
Father of RadioactivityFather of Radioactivity Discovered nuclear Discovered nuclear
radiation in 1896.radiation in 1896. Shared his findings Shared his findings
with Marie and with Marie and Pierre Currie in Pierre Currie in Paris, France.Paris, France.
Marie and Pierre Marie and Pierre CurieCurie
Discovered the Discovered the radioactive elements radioactive elements Radium and Polonium.Radium and Polonium.
Radioactive ElementsRadioactive Elements
Look at the periodic tableLook at the periodic tableWhich elements do you think have Which elements do you think have
too many too many protons and neutrons to fit protons and neutrons to fit in their nucleus without leaking out?in their nucleus without leaking out?
Are there any other elements that Are there any other elements that might have radioactive ISOTOPES?might have radioactive ISOTOPES?
How does radiation occur?How does radiation occur?
Atoms are radioactive only if there is Atoms are radioactive only if there is not enough strong force (binding not enough strong force (binding energy) to hold the nucleus together. energy) to hold the nucleus together.
DecayDecay
When particles leak out and the When particles leak out and the number of protons change……the number of protons change……the atom changes into a different atom changes into a different element.element.
When will my nucleus overflow?When will my nucleus overflow?
For ‘smaller’ elements the nucleus is For ‘smaller’ elements the nucleus is stablestable when the when the neutron to proton ratio neutron to proton ratio is 1:1. (In other words, for every one is 1:1. (In other words, for every one neutron there is one proton.) When this neutron there is one proton.) When this balance is upset, too many neutrons, the balance is upset, too many neutrons, the nucleus will become nucleus will become unstableunstable and it and it overflows... overflows... decaysdecays..
For ‘larger’ elements the ratio is stable at For ‘larger’ elements the ratio is stable at 3:2; and unstable when too many or too 3:2; and unstable when too many or too few neutrons are present.few neutrons are present.
3 Types of Radiation3 Types of Radiation
1.1. Alpha particlesAlpha particles
2.2. Beta particlesBeta particles
3.3. Gamma RaysGamma Rays
Alpha ParticlesAlpha Particles
Made of 2 protons Made of 2 protons and 2 neutronsand 2 neutrons
+2 charge+2 chargeLike a Helium Like a Helium
nucleusnucleus Slow movingSlow movingStopped by paperStopped by paper
Beta ParticlesBeta Particles
High speed electronHigh speed electronCharge of –1Charge of –1No massNo massStopped by plastic or Stopped by plastic or
woodwood
Formed when a neutron breaks down Formed when a neutron breaks down into a new proton and new electroninto a new proton and new electron
Gamma RaysGamma Rays
Most penetrating Most penetrating form of radiationform of radiation
Pure energyPure energyCan damage Can damage
human tissueshuman tissuesStopped by lead Stopped by lead
or concreteor concrete
Uses of RadiationUses of RadiationSmoke alarms Smoke alarms contain a weak contain a weak source made of source made of Americium-241Americium-241. . AlphaAlpha particles are particles are emitted from here. emitted from here.
In nuclear medicine, Beta particles are used in PET scans to image the brain to detect abnormalities.
Gamma radiation is also used to sterilize hospital equipment, especially plastic syringes that would be damaged if heated. They are also used in treatment of cancerous tumors.
Fun Science Word of the DayFun Science Word of the Day
TransmutationTransmutation
An atom of one element changing An atom of one element changing (mutating) into another element (mutating) into another element during radioactive decay.during radioactive decay.
Nuclear DecayNuclear Decay
Alpha EmissionAlpha Emission
He Th U 42
23490
23892
parentnuclide
daughternuclide
alphaparticle
Numbers must balance!!