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C HAPTER N INE : N UCLEAR C HANGES Section One: What is Radioactivity?

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Presentation on theme: "C HAPTER N INE : N UCLEAR C HANGES Section One: What is Radioactivity?"— Presentation transcript:

1 C HAPTER N INE : N UCLEAR C HANGES Section One: What is Radioactivity?

2 N UCLEAR R ADIATION Radioactivity is when particles or energy are emitted from an unstable nucleus. Nuclear radiation is the particles released.

3 T YPES OF N UCLEAR R ADIATION Radiation TypeSymbolMass (kg)Charge Alpha Particle6.646x10 -27 +2 Beta Particle9.109x10 -31 Gamma Raynone0 Neutron1.675x10 -27 0

4 T YPES OF N UCLEAR R ADIATION ( CONT.) Alpha particles are two protons and two neutrons. Beta particles are an electron. Gamma particles are energy. If a nucleus is unstable, neutron emission may occur. Half-life is the time it takes for half of the substance to decay. Carbon-14 decays to carbon-12, so the amount of carbon-14 left determines the time it decayed in

5 C HAPTER N INE Section Two: Nuclear Fission and Fusion

6 N UCLEAR F ORCES Protons and neutrons are packed tightly in the nucleus. The stability of the nucleus depends on the nuclear forces between the protons and neutrons. Neutrons contribute to the stability of the nucleus by not causing two positive charges to be directly next to each other.

7 N UCLEAR F ISSION When heavier nuclei are split into lighter nuclei. Energy is released. The neutrons released can cause a chain reaction. More and more nuclei may split. These reactions can be controlled.

8 N UCLEAR F USION Lighter nuclei are combined to form heavier nuclei. Requires energy. Typically occurs on the sun where hydrogen combines to form helium.

9 C HAPTER N INE Section Three: Nuclear Radiation Today

10 W HERE IS R ADIATION ? Background radiation occurs everywhere. Radiation is measured in rems. 5rems/yr limit Levels of exposure depend on location. Some activities increase nuclear radiation exposure. Smoking 1 ½packs of cigarettes/day = 8rems/yr Flying for 720hrs = 0.267rems Giving or receiving medical Xrays = 0.1rems/yr

11 B ENEFICIAL N UCLEAR R ADIATION Smoke detectors CT scanning PET and MRI Cancer treatment Agriculture

12 P OSSIBLE R ISKS Can ionize and harm tissue. High levels of radiation can cause: Cancer Radiation sickness

13 R EAL -W ORLD Person TestedRadiation Exposure Increased Cancer Risk Hiroshima Survivor27rem at once6% WWII radiologist50rem over 2 yrs0% Chernobyl visitor0.025rem0%

14 N UCLEAR P OWER Nuclear Fission: when a nuclei splits. Creates nuclear radiation. Difficult to control. Nuclear waste is costly and difficult to store. Nuclear Fusion: join two nuclei. Very difficult to provide energy for. Very little waste or pollution. Uses hydrogen which is very common. Could form radiation.


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