CHAPTER 21 NUCLEAR CHEMISTRY

NUCLEUS NUCLEONS ARE MADE UP OF PROTONS AND NEUTRONS NUCLIDE IS AN ATOM IDENTIFIED BY THE NUMBER OF PROTONS AND NEUTRONS NUCLEAR BINDING ENERGY IS THE ENERGY RELEASED WHEN A NUCLEUS IS FORMED FROM NUCLEONS

NUCLEAR REACTIONS CHANGES THE NUCLEUS OF A REACTION EXAMPLE + +

RADIOACTIVE DECAY SPONTANEOUS DISINTEGRATION OF A NUCLEUS INTO A SLIGHTLY LIGHTER NUCLEUS, ACCOMPANIED BY EMISSION OF PARTICLES, ELECTROMAGNETIC RADIATION OR BOTH

TYPES OF RADIOACTIVE DECAY TYPESYMBOLCHARGE ALPHA PARTICLE 2+ BETA PARTICLE 1- POSITRON1+ GAMMA RAY0

ALPHA EMISSION AN ALPHA PARTICLE IS TWO PROTONS AND TWO NEUTRONS BOUND TOGETHER AND IS EMITTED FROM THE NUCLEUS DURING RADIOACTIVE DECAY

EXAMPLE +

BETA EMISSION A BETA PARTICLE IS AN ELECTRON EMITTED FROM THE NUCLEUS DURING RADIOACTIVE DECAY

EXAMPLE + +

POSITRON EMISSION A POSITRON IS A PARTICLE THAT HAS THE SAME MASS AS AN ELECTRON, BUT HAS A POSITIVE CHARGE.

EXAMPLE + +

ELECTRON CAPTURE AN INNER ORBITAL ELECTRON IS CAPTURED BY THE NUCLEUS OF ITS OWN ATOM

EXAMPLE + +

GAMMA EMISSION GAMMA RAYS ARE HIGH- ENERGY ELECTROMAGNETIC WAVES EMITTED FROM A NUCLEUS AS IT CHANGES FROM THE EXCITED STATE TO A GROUND ENERGY STATE.

PRACTICE The alpha decay of iridium-174

PRACTICE The beta decay of platinum-199

PRACTICE Positron emission from sulfur-31

PRACTICE Krypton-76 undergoes electron capture

HALF LIFE-t 1/2 TIME REQUIRED FOR HALF OF THE ATOMS OF A RADIOACTIVE NUCLIDE TO DECAY

REPRESENTATIVE RADIOACTIVE NUCLIDES AND THEIR HALF-LIVES NUCLIDEHALF-LIFE 5715 YEARS 1.6 SECONDS 4.46 X 10 9 YEARS 2.41 X 10 4 YEARS

HALF LIFE CALCULATIONS t 1/2 =TIME ELAPSED X 1/HALF LIFE AMT REMAINING=STARTING AMT X (1/2) n WHERE n=THE NUMBER OF HALF-LIVES

EXAMPLE PHOSPHORUS-32 HAS A HALF LIFE OF 14.3 DAYS. HOW MANY MILLIGRAMS OF PHOSPHORUS-32 REMAIN AFTER 57.2 DAYS IF YOU START WITH 4.0 mg OF THE ISOTOPE? 0.25mg

PRACTICE If the half-life for the radioactive decay of zirconium-84 is 26 minutes and I start with a 175 gram sample, how much will be left over after 104 minutes? 10.9g

PRACTICE ASSUMING A HALF-LIFE OF 1599 YEARS, HOW MANY YEARS WILL BE NEEDED FOR THE DECAY OF 15/16 OF A GIVEN AMOUNT OF RADIUM-226? 6396 YEARS