Isotopes and Radioactivity Isotopes Isotopes are atoms of

Isotopes and Radioactivity

Isotopes • Isotopes are atoms of an element having the same number of protons but different numbers of neutrons. • How many neutrons? – Mass number – atomic number = number of neutrons

Sample problems

What is radioactive decay? • This occurs when an unstable atomic nucleus changes into another nucleus by emitting one or more particles and energy • A nucleus that is unstable is radioactive • Radioactive nuclei have found many uses in science and medicine – Iron-59 (an isotope) can be injected into a person’s bloodstream to show blood circulation – pg 303

Uses of radioactive decay • Other uses: – Detection of cancer and killing of cancer cells • using coblat-60 to stop the growth of brain tumors – Preserving food • The radiation kills bacteria, fungi, insects, and other pests that spoil food

Discovery • 1896, Antoine-Henri Bequerel -> uranium • Marie Curie separated radioactive elements in uranium mineral – With her husband Pierre, discovered polonium and radium • Most radioactive elements are heavier elements, near the bottom of the periodic table

Half-Life • Uranium is still found in nature because of how long it takes to decay • Half-life is the time it takes for a sample of radioactive isotope to decay to half its original mass • EXAMPLES: – Uranium-235 takes 713 million years

How are elements discovered and named? • Some elements are not found in nature (or found in very small amounts) • Synthetic elements are radioactive elements made by scientists in labs or created during nuclear reactions • Technetium (43) was the first synthetic element • Visualizing Synthetic elements pg 308

Discovery • First they must be discovered and officially confirmed by International Union or Pure and Applied Chemistry and the International Union of Pure and Applied Physics – Write a paper – Experts review the work to support the claims made – Set of rules: must be able to be repeated, following scientific principles, show distinct chemical/physical properties

Naming • Scientists who discover the elements get to name them • They can name after people they want to honor or places of birth