NUCLEAR CHEMISTRY RADIOACTIVITY WHAT IS IT ALL SUBSTANCE

NUCLEAR CHEMISTRY

RADIOACTIVITY – WHAT IS IT? • ALL SUBSTANCE ARE MADE OF ATOMS. THESE HAVE ELECTRONS (E) AROUND THE OUTSIDE, AND A NUCLEUS IN THE MIDDLE. THE NUCLEUS CONSISTS OF PROTONS (P) AND NEUTRONS (N), AND IS EXTREMELY SMALL. (ATOMS ARE ALMOST ENTIRELY MADE OF EMPTY SPACE!) • IN SOME TYPES OF ATOM, THE NUCLEUS IS UNSTABLE, AND WILL DECAY INTO A MORE STABLE ATOM. THIS RADIOACTIVE DECAY IS COMPLETELY SPONTANEOUS. THE ENERGY THAT IS RELEASED FROM THE NUCLEUS OF THE ATOM IS RADIATION.

RADIOACTIVITY – WHAT IS IT?

RADIOACTIVITY – ALPHA PARTICLES

RADIOACTIVITY – BETA PARTICLES

RADIOACTIVITY – GAMMA WAVES

RADIOACTIVITY – SUMMARY

ISOTOPE NOTATION • ISOTOPE NOTATION INCLUDES ADDITIONAL INFORMATION ABOUT AN ISOTOPE. IN ADDITION TO THE CHEMICAL SYMBOL, THE MASS NUMBER AND THE ATOMIC NUMBER ARE INCLUDED. THIS ALLOWS INFORMATION ABOUT THE NUCLEUS TO BE DETERMINED.

NUCLEAR DECAY REACTIONS • SOME ELEMENTS ARE NATURALLY UNSTABLE • THEY TEND TO UNDERGO ALPHA-DECAY OR BETA-DECAY TO BECOME MORE STABLE. • THEY MAY TAKE SEVERAL STEPS IN ORDER TO ACHIEVE THIS, THUS WE OBSERVE DECAY CHAINS (ALSO KNOWN AS SERIES DECAY) FOR MOST RADIOACTIVE ELEMENTS. • FOR EXAMPLE, IT TAKES U-238 14 STEPS OF ALPHA AND BETA DECAY TO BECOME COMPLETELY STABLE

IDENTIFYING ALPHA AND BETA DECAY REACTIONS

IDENTIFYING ALPHA AND BETA DECAY REACTIONS

BALANCING NUCLEAR DECAY REACTIONS

DECAY CHAIN OF U-238 • STEP 1: ALPHA DECAY OF URANIUM-238 __________________________ • STEP 2: BETA DECAY REACTION __________________________ • STEP 3: BETA DECAY REACTION __________________________ • NOW YOU COMPLETE THE REST ……………

FISSION AND FUSION • FISSION: FISSION IS THE PROCESS OF SPLITTING AN ATOM. • FUSION: NUCLEAR FUSION IS THE PROCESS BY WHICH MULTIPLE SMALL ATOMIC NUCLEI JOIN TOGETHER TO FORM A HEAVIER NUCLEUS.

FISSION AND FUSION

HALF LIFE • WHEN RADIOACTIVE ISOTOPES DECAY, THEY DO SO EXPONENTIALLY. THEIR RATE OF DECAY IS DETERMINED THROUGH AN UNDERSTANDING OF HALF-LIFE. • HALF-LIFE IS THE AMOUNT OF TIME IT TAKES FOR HALF OF THE ATOMS OF AN UNSTABLE ISOTOPE TO DECAY. • ATOMS WITH SHORT HALF-LIVES ARE MORE UNSTABLE THAN THOSE WITH LONG HALF-LIVES.

HALF LIFE • WHEN RADIOACTIVE ISOTOPES DECAY, THEY DO SO EXPONENTIALLY. THEIR RATE OF DECAY IS DETERMINED THROUGH AN UNDERSTANDING OF HALF-LIFE. • HALF-LIFE IS THE AMOUNT OF TIME IT TAKES FOR HALF OF THE ATOMS OF AN UNSTABLE ISOTOPE TO DECAY. • ATOMS WITH SHORT HALF-LIVES ARE MORE UNSTABLE THAN THOSE WITH LONG HALF-LIVES.

HALF LIFE EXAMPLES • RADON-222 DECAYS WITH A HALF-LIFE OF 3. 82 DAYS. IF AN INITIAL SAMPLE OF THE ELEMENT CONTAINS 1000 ATOMS, HOW LONG WILL IT TAKE FOR THE SAMPLE TO DECAY DOWN TO 125 ATOMS? YOUR TIME MUST ALWAYS START AT 0 DAYS! • SOLUTION AMOUNT TIME 1000 ATOMS 0 DAYS

HALF LIFE EXAMPLES • AN INITIAL SAMPLE OF ZINC-61 CONTAINS 215 GRAMS. AFTER 976 DAYS, THE SAMPLE SIZE HAS REDUCED TO 13. 4375 GRAMS. WHAT IS THE HALF-LIFE OF ZINC-61 ATOMS? • SOLUTION AMOUNT 215 GRAMS TIME 0 DAYS

HALF LIFE EXAMPLES • THORIUM-230 DECAYS WITH A HALF LIFE OF 80, 000 YEARS. IF AN INITIAL SAMPLE HAS A MASS OF 10. 00 GRAMS, HOW MUCH WILL REMAIN AFTER 320, 000 YEARS? • SOLUTION AMOUNT 10 GRAMS TIME ___ DAYS (YEARS)