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.)

Nuclear EnergyNuclear Energy

It’s All About the NUCLEUS!It’s All About the NUCLEUS!

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!!

Wrapping It UpWrapping It UpPractice transmutation as you follow the 4.6 Practice transmutation as you follow the 4.6

million year journey of uranium-235 to lead-207million year journey of uranium-235 to lead-207