Radioactivity

Radioactivity : Is the spontaneous breaking up of unstable nuclei to give one or more type of radiation

Radioactivity Discovered by Henri Becquerel Studying the effects of light on uranium salts Found the uranium salt was giving off some type of radiation Pierre and Marie Curie discovered polonium and radium Were given the Nobel Prize for their work

Antoine Henri Becquerel In 1896, while investigating uranium salts, Becquerel accidentally discovered radioactivity. Becquerel found that the photographic plates were fully exposed when in contact with radioactive salt.

Marie Curie Developed a theory of radioactivity techniques for isolating radioactive isotopes, and discovered two new elements, polonium and radium

Pierre Curie Pierre discovered nuclear energy, by identifying the continuous emission of heat from radium particles. He also investigated the radiation emissions of radioactive substances, which lead to the discovery of alpha, beta and gamma radiation.

Types of Radiation Alpha particles Beta particles Gamma rays

Alpha particles

He Alpha Particles Groups of 2 protons and 2 neutrons (i.e. Same as the nucleus of a helium atom) Represented as Thrown out of the nucleus of a radioactive element as it changes to a more stable nucleus He 4 2

Alpha particles

Beta Particles - Are electrons Neutron in an unstable atom changes into a proton and an electron The electron is ejected from nucleus - Beta Particle

Gamma Rays High energy electromagnetic radiation An unstable nucleus emits gamma rays in order to lose surplus energy Most dangerous of the three types

All three types of radiation detected using a Geiger-Muller Tube Video!

+ - None Type of radiation Nature Charge Example Alpha Penetrating Power Stopped by: Example Alpha Helium nuclei (2protons + 2neutrons) + Paper Americium-241 Beta Electrons - Aluminium 5mm thick Carbon-14 Gamma Waves of high energy None Several cm of lead Cobalt-60

Nuclear reactions A nuclear reaction is a process that alters the composition, structure or energy of an atomic nucleus

Nuclear reactions Alpha radiation When an atom loses an alpha particle it changes into an atom two places before it on the periodic table. The mass number decreases by 4 The atomic number decreases by 2

Nuclear reactions Radium-226  Radon-222 + alpha particle Ra  Rn + He Alpha radiation Radium-226  Radon-222 + alpha particle Mass decreases by 4 [226222] Atomic number decreases by 2 [8886] 226 222 4 Ra  Rn + He 88 86 2

Nuclear reactions - Beta radiation When an atom loses a beta particle it changes into an atom one place after it on the periodic table. The mass number stays the same. Atomic number increases by 1

Nuclear reactions Carbon-14  Nitrogen-14 + beta particle C  N + e Beta radiation Carbon-14  Nitrogen-14 + beta particle Mass number stays the same Atomic number increases by 1 14 14 C  N + e 6 7 -1

Chemical Reactions Nuclear Reactions Involves electrons rather than the nucleus Changes take place in the nucleus No new element formed New element formed No release of nuclear radiation Nuclear radiation released Chemical bonds broken and formed No bond breaking or formation

Half-Life Scientists don’t fully understand why some nuclei spontaneously break up Different radioactive isotopes break up at different rates The rate of decay of an isotope is measured by its half-life. The half-life of an element is the time taken for half of the nuclei in any given sample to decay.

Half-Life

A radioisotope (radionuclide) is an atom with an unstable nucleus. Radioisotopes A radioisotope (radionuclide) is an atom with an unstable nucleus. Uses of radioisotopes Medical– Cobalt-60 kill cancer Smoke alarms- Americium- 241 Archaeological– Carbon-14 used in carbon dating Industrial– radioisotope added to pipes to find leaks

Carbon dating Chernobyl: https://vimeo.com/112681885

Natural Radiation comes from Sources in the earth that contain radioactive isotopes. Sources from space in the form of cosmic rays Sources in the atmosphere, particularly from radon gas that is released from the earth's crust.

Natural Radiation comes from About 15% of background radiation comes from medical x-rays and nuclear medicine. About 3% of background radiation comes from other man-made sources such as: nuclear testing, power plants, and smoke detectors.