Nuclear Chemistry Nuclear Chemistry can be used to produce electrical power, diagnose and treat disease, and has been used for weapons which have changed the world forever.

Nuclear Power Plants Here, a nuclear fission reaction is used to produce large amounts of energy via generation of steam. It also produces waste that is radioactive.

Many medical tests and treatments involve the use of radioactive substances. Here, Homer Simpson’s brain is illuminated to show his skull in an X-ray. Nuclear Medicine

Characteristics of Chemical and Nuclear Reactions Chemical ReactionsNuclear Reactions 1. Occur when bonds are broken and formed. 1. Occur when nuclei emit particles and/or rays. 2. Atoms remain unchanged, though they may be rearranged. 2. Atoms are often converted into atoms of another element. 3. Involve only valance (outer) electrons. 3. May involve protons, neutrons, and electrons. 4. Associated with small energy changes. 4. Associated with large energy changes. 5. Reaction rate is influenced by temperature, pressure, concentration, and catalysts. 5. Reaction rate is not normally affected by temperature, pressure, or catalysts.

History 1895 – William Roentgen discovered that when certain ores (rocks) were hit by electrons, they gave off invisible rays that would cause photographic film to darken. He named them X-rays Marie Curie and her husband Pierre discovered that Uranium atoms in rocks emit rays and she named this process radioactivity. The particles and rays given off she called radiation.

Radioactivity- is the process in which some substances emit radiation. Radiation – the rays of energy and particles (alpha, beta, and gamma) that are emitted by radioactive materials. Radioactive atoms emit radiation because their nuclei are unstable. Unstable nuclei lose energy by emitting radiation in a spontaneous process called radioactive decay.

Types of Radiation Alpha (  )Alpha (  ) Beta (  )Beta (  ) Gamma (  )Gamma (  ) These particles are shown are your STAAR EOC formula chart in case you need them!

Alpha (  ) Alpha (  ) radiation – occurs when alpha particles are emitted. An alpha particle is a helium nucleus. It has the symbol 4 2 He or α. During alpha decay, a nucleus loses 2 neutrons and 2 protons, to become a new element. (  ) Alpha (  ) decay

Beta (  ) eta decay changes a n 0 into a p+ and an e-. Beta (  ) radiation – consists of fast moving electrons called beta particles. Each beta particle is an electron with a 1 - charge. Beta decay changes a n 0 into a p+ and an e-. (  ) Beta (  ) Decay - occurs when an isotope is unstable due to having too many neutrons.

Gamma (  )Gamma (  ) radiation – Gamma rays are high energy radiation that have no mass and no electrical charge. They are not deflected (bent) by electric or magnetic fields. Gamma rays usually accompany alpha and beta radiation and they account for most of the energy lost during the radioactive decay process. Because gamma rays have no mass, they cannot result in the formation of a new atom.

TYPE TYPE SYMBOL SYMBOL ATOMIC # CHANGE ATOMIC # CHANGE NEUTRON CHANGE NEUTRON CHANGE MASS CHANGE MASS CHANGE ALPHA (  ) ALPHA (  ) BETA (  ) BETA (  ) GAMMA (  ) by 2 by 2 He42 +2 by 4 by 4 e 0 by 1 by 1 no change no change  0 0

Penetrating Power of Radiation The above diagram shows how different types of radiation can penetrate through different materials. The most energetic radiation, gamma, γ, can penetrate most materials. Only lead and concrete are dense enough to stop most of it! Gamma rays and X-rays are similar in their energies. Have you ever worn a lead vest to protect yourself from X-rays? Dentists use them to protect you from these rays, which can harm you.

Symbolic Notation For element symbol X, the mass, m, is the superscript. It equals the protons + neutrons. The atomic number, a, of the isotope is the number of protons. A radioisotope just means it’s radioactive. All elements with atomic numbers greater than 83 are radioactive. X

Writing and Balancing Nuclear Equations In balancing nuclear equations, mass numbers and atomic numbers are conserved. This means, simply, that the sum of the subscripts (atomic numbers) on one side of the reaction will equal the sum of the subscripts on the other side. The same will be true for the superscripts (mass numbers).

Balancing Nuclear Equations Fill in the missing particle: – 1 0 n  1 1 p+____ – Pb  0 -1 e +_____ – U  Th + _____ γ – Ra  4 2 He + _____ Radium was identified in 1898 by Marie and Pierre Curie.

Transmutation Transmutation is when an atom of one type changes to an atom of a different type. So far, the nuclear reactions we have seen occur spontaneously. That is, they occur “on their own.” Radioactive elements decay naturally. For example, radium is an element that occurs naturally in an ore called “pitchblende.” Radium undergoes alpha decay to form radon, a noble gas. Radon is a radioactive gas that seeps up from the earth Ra  Rn He

Induced Transmutation Induced transmutation occurs when one particle is bombarded, or hit, with another particle and transmutation then occurs. Scientists do this in “atom smashers” or particle accelerators. All elements beyond uranium on the periodic table have been produced this way. Ex: U n  Np β Ex: Pu He  1 0 n Cm Notice that in the above reactions, mass numbers and atomic numbers are conserved. (Totals are the same on both sides.)

Fusion Fusion is a nuclear reaction in which atomic nuclei are combined. The sun is powered by fusion reactions. Within the Sun, hydrogen atoms fuse together to form helium atoms and release GINORMOUS amounts of energy!

Fission Fission means the splitting of atoms into fragments Nuclear power plants use fission to produce electrical power. The most famous example is when uranium-235 is bombarded with neutrons to form other, smaller isotopes, as well as more neutrons. These neutrons then go on to strike other uranium atoms in what is known as a “chain reaction”. The reaction is controlled by “control rods” The explosion of an atom bomb is an example of an uncontrolled chain reaction.

Atomic Bombs Fission was used to make atomic bombs used during World War II!

Little Boy Little Boy was the name of the bomb exploded over Hiroshima 1945, killing thousands of Japanese.

Radioactive Decay Radioactive elements are still around after 15 billion years. Why? Because some of them decay very, very slowly. The half-life of an isotope is defined as the time it takes for one-half of a radioisotope’s nuclei to decay.

Radiation Safety Radioactive waste from nuclear power plants must be stored underground, and will remain radioactive for hundreds or years or even longer Both X-rays and gamma rays are very damaging to living tissues.