3. NUCLEAR FORCE holds protons together in a nucleus. - protons are POSITIVE and repel each other. - When packed with NEUTRONS a stronger force, called NUCLEAR FORCE, binds them together. → Only works when they are CLOSELY packed together.

B. RADIOACTIVE decay occurs when an atom releases nuclear particles and energy When PROTONS are ejected it changes the ATOMIC number. It changes one ELEMENT to another Known as TRANSMUTATION

1. ALPHA particle Two PROTONS and two NEUTRONS are released during transmutation (makes a new element) b. Causes the ATOMIC NUMBER to decrease by TWO.

2. BETA particle A NEUTRON splits into an ELECTRON and a PROTON. Releases a HIGH-ENERGY electron from the nucleus This ADDS a PROTON to the nucleus, LOSES a NEUTRON, and CHANGES the element.

Atomic number increases by ONE The MASS of the element stays almost the SAME (WHY?)

Question: What charge is an alpha and beta particle? - Alpha = positive - Beta = negative What does alpha and beta transmutation do to the atomic number of an atom? - Alpha = DECREASES atomic number by 2 - Beta = INCREASES atomic number by 1

C. HALF-LIFE of a radioactive isotope = amount of time it takes for HALF the sample to DECAY Half-lives range in length from fractions of a SECOND to BILLIONS of years If you have 8g of iodine-131 (half-life = 8 days), after 8 days you should have 4 GRAMS left. After EIGHT more days, you would have TWO GRAMS left.

Age of the EARTH Earth was once thought to be 98 MILLION YEARS old. Actually, it is BILLIONS of years old (about 4.5) The discovery of RADIOACTIVITY lead to this discovery. Decay of URANIUM supplied the heat to keep Earth’s CORE melted/molten.

Discovery of RADIATION It was ACCIDENTAL (By a scientist named Henri BECQUEREL) minerals containing uranium darkened PHOTOGRAPHIC film, and led to the discovery of radioactivity. Marie and Pierre CURIE isolated TWO new elements that were the source of most of the radioactivity of uranium ore. Named: RADIUM & POLONIUM They all won the NOBEL PRIZE in 1903

What are two ways radioactive decay can occur? Through the release of alpha particles, two protons and two neutrons Or Through the release of a beta particle, a high-energy electron from a split neutron.