Isotope: same element (same #P) different number of neutrons (different mass #) Carbon-12 has 6 protons and 6 neutrons Carbon -14 has 6 protons and 8 neutrons Therefore, C-12 and C-14 are isotopes

 Carbon-14  C-14 Atomic Mass Atomic Number Symbol Element Name

 When the size and mass of the nucleus becomes large (greater than atomic #83), the element is known to be radioactive (unstable) because it decays.  Examples: ▪ Pu-239 (94 protons) ▪ U-238 (92 protons)  When the ratio of neutrons to protons is greater than 1:1 (for light nuclei), the element is also radioactive.  Examples: ▪ Carbon-14 ▪ Lithium-7

 Different than mass #  Weighted average of all naturally occurring isotopes of an element

Weighted Average: You have to take into account the amount of each isotope present in a sample 1. Convert % to a decimal. 2. Multiply the mass by the decimal. 3. All products are added together.

If 75.0% of the isotopes of an element have a mass of 35.0 amu and 25% of the isotopes have a mass of 37.0 amu, what is the atomic mass of the element? 0.75 x 35 = 26.25amu 0.25 x 37 = amu 35.5 amu Does this answer make sense?

 Radioactive atoms emit radiation because their nuclei are unstable*.  Unstable nuclei lose energy by emitting radiation in a spontaneous process called radioactive decay.  Radioactive decay continues until stable, non-radioactive atoms form. They are often of a different element.

 Occurs when nuclei are unstable.  For any element, an isotope that is unstable is called a radioisotope.

 Unstable nucleus emits an alpha particle (α, )  Decreases the mass number by 4 and the atomic # by 2  Associated with heavy nuclei (above 83)

 Unstable nucleus emits a beta particle (β-, )  Turns a neutron into a proton ▪ Decreases N:P ratio  Favorable when the N:P ratio is high (above 1.0)  Found above the band of stability

 An unstable nucleus emits a positron (β+, )  Proton turns into a neutron  Favorable when the N:P ratio is low(below  1.0)  N:P increases  Isotopes found below the band of stability

 Begins with one nucleus that spontaneously decays. ***Always has ONE REACTANT.

 The atomic mass one side of the arrow has to equal the mass on the other side of the arrow  The atomic number one side of the arrow has to equal the atomic number on the other side of the arrow

Nuclear involve the nucleus of atoms. Radioactive elements have unstable nuclei. Unstable nuclei will release particles until a stable nuclei results

Which particle is the most massive (has the largest mass)? Which particle has no mass? alpha gamma (type of electromagnetic radiation)

 When a nucleus decays, it emits particles. ParticleMassChargeSymbol Penetrating Power Alpha 4 amu2+ , 2 4 He Low Beta0 amu1-  -, -1 0 e Moderate Positron0 amu1+  e Moderate Gamma0 amunone , 0 0  High

Natural Transmutation: occurs spontaneously releasing either: Alpha particle Beta particle Positron particle Gamma radiation

Alpha Decay 252 Md 227 Ac 221 Fr 207 At 181 Ir He 4242

Beta Decay 6363 Li Mg Hg Co 0 β Ca

Positron Decay 0 +1 β Se Si Al Sc 8484 Be

Which particle is emitted when an atom of Kr-85 spontaneously decays? Which list of radioisotopes contains an alpha emitter, a beta emitter, and a positron emitter? (1) C-14, N-16, P-32 (2) Cs-137, Fr-220, Tc-99 (3) Kr-85, Ne-19, Rn-222 (4) Pu-239, Th-232, U-238 Beta ( β-)

What is the half-life and decay mode of Rn-222? (1) 1.91 days and alpha decay (2) 1.91 days and beta decay (3) 3.82 days and alpha decay (4) 3.82 days and beta decay

Artificial Transmutation: forcing decay by bombarding a nuclei with a high energy particle

 Radioactive Dating:  Carbon-14 (once living things)  U-238 (rocks)  Tracing Chemical and Biological Processes  Radioactive tracers are injected into the body and then x- rayed ▪ Radioactive substance shows up on the X-ray  Detecting and Treating Disease  Sr-90:diagnosing and treating bone cancer  I-131: diagnosing and treating thyroid disorders  Co-60, Tc-99:cancer treatment  Kill Bacteria in Foods