7.2-Half-Life7.2-Half-Life7.3- Nuclear Rx 7.3- Nuclear Rx

Hulk smash! GRR! I’m going to teach you about half-life and nuclear Rx!

What is a half-life?What is a half-life?

The rate of radioactive decay can be The rate of radioactive decay can be compared using a quantity called compared using a quantity called half-lifehalf-life

Ex. The half-life of strontium-90 is 29 Ex. The half-life of strontium-90 is 29 years. If you have 10.0g strontium-years. If you have 10.0g strontium-90 today, 29 years from now, you will 90 today, 29 years from now, you will have 5.0g left. have 5.0g left.

Isotopes Isotopes

An An isotope isotope of an element have nuclei of an element have nuclei with the same number of protons (the with the same number of protons (the same "same "atomic numberatomic number") but different ") but different numbers of neutrons. Therefore numbers of neutrons. Therefore isotopes have different "isotopes have different "mass mass numbersnumbers", which is the total number ", which is the total number of nucleons (protons plus neutrons).  of nucleons (protons plus neutrons). 

Mass number= atomic number+ Mass number= atomic number+ neutronsneutrons

Isotopes(pg2)Isotopes(pg2)

Parent isotopeParent isotope: the isotope that : the isotope that undergoes radioactive decayundergoes radioactive decay

Daughter isotopeDaughter isotope: The stable : The stable product of radioactive decayproduct of radioactive decay

Subatomic Particles Subatomic Particles

Quiz Time!!! Quiz Time!!!

1.1. What is an isotope?What is an isotope?

2.2. What are the two types of isotopes?What are the two types of isotopes?

3.3. What is a half-life? What is a half-life?

4.4. Name 3 subatomic particles and Name 3 subatomic particles and their symbols. their symbols.

Carbon DatingCarbon Dating

We can measure how the radioactivity We can measure how the radioactivity in plant or animal remains has changed in plant or animal remains has changed over time and calculate the age.over time and calculate the age.

All organisms on Earth contain carbon.All organisms on Earth contain carbon. Radiocarbon dating Radiocarbon dating is the process of is the process of

determining the age of an object by determining the age of an object by measuring the amount of carbon-14 in measuring the amount of carbon-14 in that object. that object.

Carbon Dating(pg.2) Carbon Dating(pg.2)

Carbon’s isotopes include carbon-12 Carbon’s isotopes include carbon-12 and carbon-14and carbon-14

When an organism is alive, the ratio When an organism is alive, the ratio of carbon-14 atoms to carbon-12 of carbon-14 atoms to carbon-12 atoms remains nearly constant.atoms remains nearly constant.

When an organism dies, that ratio When an organism dies, that ratio decreases with time. decreases with time.

Hence, radiocarbon dating was born. Hence, radiocarbon dating was born.

Decay Curve Decay Curve

A A decay curvedecay curve is a curved line on a is a curved line on a graph that shows the rate at which graph that shows the rate at which radioisotopes decay. radioisotopes decay.

Ex. Ex.

Radioactive DecayRadioactive Decay

Radioactive decay is the process in Radioactive decay is the process in which unstable nuclei lose energy by which unstable nuclei lose energy by emitting radiation. emitting radiation.

Isotopes that are capable of Isotopes that are capable of radioactive decay are called radioactive decay are called radioisotopes. radioisotopes.

Radioactive DecayRadioactive Decay

Alpha Radiation Alpha Radiation An alpha particle is a positively charge atomic An alpha particle is a positively charge atomic

particle that has the same combination of particle that has the same combination of particles as the nucleus of a helium atom. particles as the nucleus of a helium atom.

It has an electrical charge of 2+It has an electrical charge of 2+ A single sheet of paper stops alpha particlesA single sheet of paper stops alpha particles

Symbol:Symbol:

Video Time!!! Video Time!!!

http://www.youtube.com/watch?v=je9_http://www.youtube.com/watch?v=je9_RtwhjWgRtwhjWg

Radioactive DecayRadioactive Decay

Beta RadiationBeta Radiation A beta particle is an electron.A beta particle is an electron. It has an electrical charge of -1. It has an electrical charge of -1. It requires a thin sheet of aluminum foil to block. It requires a thin sheet of aluminum foil to block. Symbol: Symbol:

Video Time!! Video Time!!

http://www.youtube.com/watch?v=t-NDhttp://www.youtube.com/watch?v=t-NDf2JY6Pkf2JY6Pk

Radioactive DecayRadioactive Decay

Gamma RadiationGamma Radiation It consists of high-energy, short-It consists of high-energy, short-

wavelength radiation.wavelength radiation. Blocked by thick blocks of dense Blocked by thick blocks of dense

materials i.e. lead and concrete. materials i.e. lead and concrete. Gamma decay Gamma decay results from a results from a

redistribution of energy within the redistribution of energy within the nucleus.nucleus.

Symbol: Symbol:

Video Time!!! Video Time!!!

http://www.youtube.com/watch?v=PW_http://www.youtube.com/watch?v=PW_KNP3gllsKNP3glls

Can you think of an example of a product of gamma radiation?

Fission vs FusionFission vs Fusion FissionFission is the splitting of a large is the splitting of a large

atom into two or more smaller ones. atom into two or more smaller ones. FusionFusion is the fusing of two or more is the fusing of two or more

lighter atoms into a larger one. lighter atoms into a larger one.

QUIZ TIME!!! QUIZ TIME!!!

Name the 3 different radiation types.Name the 3 different radiation types. Define fission.Define fission. Define fusion. Define fusion. True or false: Gamma radiation is a True or false: Gamma radiation is a

stream of gamma particles.stream of gamma particles.