- WELCOME TO NUCLEAR CHEMISTRY PART ONE.
THIS WILL HAVE A BRIEF INTRODUCTION AND A REVIEW
OF WHAT WE'VE LEARNED ABOUT THE NUCLEAR STRUCTURE OF ATOMS.
LET'S GET STARTED. ALL RIGHT.
HERE, WE HAVE THREE SYMBOLS FOR VARIOUS ISOTOPES OR CARBON.
SO, THIS A QUICK REVIEW.
THIS WOULD BE A GREAT PLACE
TO JUST PAUSE AND ANSWER ALL THE QUESTIONS
AND CHECK IN TO SEE WHERE YOU ARE WITH YOUR KNOWLEDGE
OF NUCLEAR STRUCTURE, RIGHT?
SO, AS WE LOOK AT CARBON-12,
WE WOULD SEE THAT IT HAS SIX PROTONS
AND IT WOULD HAVE SIX NEUTRONS,
RIGHT? WE FOUND THE NEUTRONS
BECAUSE REMEMBER THAT THIS TOP VALUE HERE,
RIGHT, THAT'S THE NUMBER OF PROTONS
PLUS THE NUMBER OF NEUTRONS,
AND THEN HERE, WE HAVE Z.
AND I THINK I'VE GIVEN AWAY THE ANSWERS ALREADY
TO THE LATER QUESTIONS, RIGHT?
SO, CARBON-13, OF COURSE,
HAS SIX PROTONS AS WELL BUT HAS SEVEN NEUTRONS.
AND THEN, OF COURSE,
CARBON-14 ALSO HAS SIX PROTONS BUT NOW,
IT HAS EIGHT NEUTRONS, RIGHT?
SO, WHAT'S THE SAME ABOUT ALL THESE ISOTOPES,
RIGHT, IT'S DEFINITELY,
RIGHT, IT'S THE NUMBER OF PROTONS, RIGHT?
WHAT'S DIFFERENT ABOUT EACH OF THESE ISOTOPES,
RIGHT, THE NUMBER OF NEUTRONS.
ALL RIGHT.
SO, WHAT DOES THE SUBSCRIPT, RIGHT, THE SUPERSCRIPT--
OR EXCUSE ME,
SUBSCRIPT IS SIX, RIGHT?
THAT REPRESENTS THE NUMBER OF PROTONS.
AND WE REMEMBER THAT THE SYMBOL THERE IS Z, RIGHT,
FOR THE NUMBER OF PROTONS.
AND THEN, RIGHT, THE SUPERSCRIPT,
THE 12, 13, 14, THAT REPRESENTS THE NUMBER OF PROTONS
PLUS THE NUMBER OF NEUTRONS.
AND WE REMEMBER THAT THAT SYMBOL IS A, RIGHT, OH,
LET'S GO THROUGH THE NAMES, RIGHT?
SO, THIS WOULD BE THE MASS NUMBER,
WHICH MAKES SENSE BECAUSE IT'S THE PROTONS
AND THE NEUTRONS THAT CREATE THE MASS OF AN ATOM.
AND THEN FOR COMPLETION, RIGHT,
THE SYMBOL Z IS DESCRIBED AS THE ATOMIC NUMBER,
WHICH ALSO MAKES SENSE BECAUSE WE SEE THAT THE IDENTITY
OF AN ATOM IS DETERMINED BY THE NUMBER OF PROTONS.
ALL RIGHT.
SO, THAT'S ENOUGH FOR THE QUICK REVIEW.
NOW, LET'S SEE WHAT HAPPENS WHEN WE HAVE RADIOISOTOPES.
SO, WHAT DOES THAT MEAN?
SO, A RADIOISOTOPE IS BASICALLY THOSE ARE UNSTABLE ISOTOPES.
SO, SOME ISOTOPES ARE STABLE BUT OTHERS ARE NOT.
AND SO, BASICALLY, IT'S WHEN WE HAVE TOO MANY PROTONS,
RIGHT, OR NEUTRONS.
THAT CREATES AN UNSTABLE NUCLEUS.
AND SO, THAT IS GOING TO CREATE A CONDITION
WHERE RADIOACTIVE DECAY OCCURS.
THE NUCLEUS OF THE RADIOACTIVE ISOTOPE
UNDERGOES A NATURAL PROCESS TO BECOME MORE STABLE.
AND SO, HOW DOES THE NUCLEUS BECOME MORE STABLE?
IT HAS TO RELEASE SUBATOMIC PARTICLES AND/OR LIGHT
OR HIGH ENERGY ELECTROMAGNETIC RADIATION, RIGHT?
AND/OR LIGHT.
AND LIGHT,
THE FANCY NAME FOR LIGHT IS ELECTROMAGNETIC RADIATION.
OKAY. SO, IT'S ONE THING--
IT'S IMPORTANT THAT WE UNDERSTAND
THAT RADIOACTIVITY IS JUST PART OF BEING ON EARTH,
RIGHT? WE HAVE--
WE'RE ALL EXPOSED TO BACKGROUND RADIATION EVERYDAY
AND THIS IS THE RADIATION THAT OCCURS FROM NATURAL SOURCES,
AND THEN DEPENDING ON WHAT'S GOING ON IN OUR LIFE
AND WHERE WE LIVE,
THERE ARE ARTIFICIAL SOURCES AS WELL.
SO, LET'S LOOK AT THE COMMON EXPOSURE
FROM LIVING ON PLANET EARTH, ALL RIGHT?
SO, LOOK AT ALL THE NATURAL SOURCES, RIGHT?
COSMIC RAYS PENETRATING THROUGH OUR ATMOSPHERE,
TERRESTRIAL RADIATION FROM ROCKS AND BUILDINGS,
INSIDE OUR BODY,
WE HAVE NATURALLY OCCURRING ISOTOPES,
POTASSIUM AND RADIUM.
AND THEN THERE'S RADON IN THE AIR, RIGHT?
SO, BEING ALIVE ON EARTH,
WE ARE GOING TO BE EXPOSED TO APPROXIMATELY
294 MILLIREMS PER YEAR.
WE'LL TALK ABOUT THESE UNITS IN A FUTURE TUTORIAL.
NOW, WHERE DID THE ARTIFICIAL SOURCES COME FROM?
RIGHT? WELL, IF WE--
OOPS, WE GOT A TYPO THERE.
IF WE HAVE A MEDICAL X-RAY
OR WE'RE RECEIVING A NUCLEAR MEDICINE TREATMENT,
SOME CONSUMER PRODUCTS,
TELEVISION MONITORS AND SCREENS, SMOKE DETECTORS,
IF WE'RE CLOSE TO A NUCLEAR POWER PLANT,
NOTICE THE CONTRIBUTION THERE AND THEN ALL OTHER SOURCES.
SO, NOW, THESE TWO, YOU KNOW,
IT DEPENDS ON WHAT'S GOING ON IN OUR LIFE.
WE MAY OR MAY NOT BE GETTING X-RAYS
OR RECEIVING NUCLEAR MEDICINE TREATMENTS.
LOOK AT THE DOSE THERE.
THAT IS HUGE, RIGHT?
SO, THREE-- SO THAT'S 53 MILLIREM PER YEAR RIGHT THERE.
SO, WHAT DO WE NOTICE?
WE NOTICED THAT THE NATURAL SOURCES OF RADIATION ARE 80
TO 96 PERCENT OF TOTAL EXPOSURE.
AND THE MAN-MADE, RIGHT,
IF WE IGNORE THIS, WE'RE DOWN TO 12 MILLIREM,
AND ONLY 4 PERCENT OF EXPOSURE.
SO, I THINK THAT IGNORANCE AND FEAR CAN BE COMMON BEDFELLOWS
AND I THINK SOME OF THE FEAR ASSOCIATED
WITH NUCLEAR CHEMISTRY AND NUCLEAR ENERGY IS RELATED
TO NOT UNDERSTANDING EXACTLY WHAT'S GOING ON.
SO, I THINK IT'S REALLY HELPFUL TO LOOK AT THE--
WHERE WE GET OUR EXPOSURES
SO WE CAN KEEP EVERYTHING IN PERSPECTIVE.
AND NOW, WE'LL DO AN INTRODUCTION
TO THE DIFFERENT TYPES OF RADIATION, ALL RIGHT?
SO, LET'S IMAGINE THAT WE HAVE A LEAD BOX
AND IT CONTAINS A VARIETY OF RADIOACTIVE SOURCES.
AND THEN WE ALIGN THE BEAMS TO NARROW IT AND THEN,
WE ALLOW THE BEAM TO TRAVEL THROUGH A MAGNETIC FIELD,
RIGHT, AND SO WHAT DO WE NOTICE?
WE NOTICE THAT THE ALPHA RAYS ARE
ATTRACTED TO THE NEGATIVE PLATE.
THE GAMMA RAYS ARE NOT AFFECTED BY THE MAGNETIC FIELD.
AND THE BETA RAYS ARE ATTRACTED TO THE POSITIVE PLATE.
SO, THIS IS GOING TO HELP US UNDERSTAND
THE ELECTROMAGNETIC ASPECTS OF RADIOACTIVE DECAY.
SO, HERE'S A TABLE THAT SUMMARIZES.
SO, WE'LL START HERE
AND THIS WILL BE OUR ORIGINAL ELEMENT, ALL RIGHT?
AND SO, WE'LL JUST--
IT CAN BE ANY ELEMENT.
SO, I'LL JUST BE GENERIC HERE.
SO, JUST FOR SIMPLICITY, I'LL USE THE SAME SYMBOLS.
IT WOULD BE PRETTY UNCOMMON THAT A SINGLE ELEMENT
WOULD HAVE ALL OF THESE DIFFERENT ISOTOPES,
WOULD HAVE ALL OF THESE DIFFERENT FORMS OF DECAY
BUT IT WILL--
I THINK IT WILL BE INSTRUCTIVE, ALL RIGHT?
SO, IF OUR ORIGINAL ELEMENT IS AN ALPHA EMITTER, BASICALLY,
WHAT IT'S RELEASING IS A HELIUM NUCLEUS, RIGHT?
SO, THE HELIUM NUCLEUS CAN BE DESCRIBED AS AN--
WITH AN ALPHA SYMBOL
AND REMEMBER THAT IT IS A HELIUM NUCLEUS.
SO, IT WOULD HAVE CHARGE.
AND THAT'S THE POSITIVE CHARGE THAT'S ATTRACTED
TO THE NEGATIVE PLATE. OKAY.
AND THEN WE WILL GET A NEW ELEMENT, RIGHT?
SO, BECAUSE OF THE HELIUM NUCLEUS, RIGHT,
HAS A MAS NUMBER OF FOUR AND AN ATOMIC NUMBER OF TWO.
SO, THINK ABOUT YOUR MASS BALANCE, RIGHT?
CHEMICAL REACTIONS,
EVEN NUCLEAR REACTIONS OBEY THE CONSERVATION OF MASS.
SO, OVER HERE, WE WILL GET A DAUGHTER
AND I THINK IT'S VERY INTERESTING
ABOUT FEMININE QUALITIES.
AND SO, WHAT WILL HAPPEN TO OUR DAUGHTER, RIGHT, WELL,
THE ORIGINAL NUCLEUS HAD Z PROTONS
AND TWO WERE LOST IN THE ALPHA PARTICLE, Z
- 2. AND THEN THE ORIGINAL MASS NUMBER WAS A BUT NOW WE'VE LOST,
RIGHT, TWO PROTONS AND TWO NEUTRONS
FROM OUR ALPHA PARTICLE,
SO, WE WOULD SUBTRACT FOUR.
AND SO, THIS WOULD BE THE ISOTOPE
OF THE DAUGHTER PRODUCT.
NOW, WE LOOK AT THE ORIGINAL ELEMENT AGAIN BUT THIS TIME,
WE'LL SEE IT AS A BETA EMITTER.
SO, BETA, THE SYMBOL THERE CAN BE--
THERE WILL BE--
THERE'S NO CHANGE OF MASS
BUT THE MINUS SIGN WILL HELP US UNDERSTAND BETA, THAT, RIGHT?
SO, WHAT DO WE WANT TO DO HERE?
WE'RE GOING TO LOSE A MINUS ONE.
SO, WHEN WE LOOK AT THE DAUGHTER,
WE SAY THEIR PARENT WAS ORIGINALLY A Z
AND NOW WE'RE GOING TO LOSE A
- 1. AND NOTICE THAT THE MASS NUMBER DOESN'T CHANGE.
AND WE WILL EXPLORE EXACTLY
WHAT'S HAPPENING IN A SUBSEQUENT TUTORIAL.
SO, WE'LL JUST TAKE IT ONE STEP AT A TIME.
AND SO, WE COULD REWRITE THIS SIMPLIFYING, RIGHT?
SO BASICALLY WHAT HAPPENS HERE, RIGHT,
IS THAT THE NUCLEUS GAINED A PROTON.
SO, HERE WE HAVE A NEUTRON BECOMING A PROTON
PLUS A BETA PARTICLE.
I GUESS I'LL GIVE YOU THAT RIGHT NOW. OKAY.
A POSITRON EMITTER IS BASICALLY THE OPPOSITE OF A BETA EMITTER.
AND SO, WE USE THE SAME BETA SYMBOL BUT NOW WE PUT THE +1.
SO, THEN THE SYMBOL IS EXACTLY
LIKE THE PREVIOUS ONE EXCEPT WE SWITCH THE SIGN.
SO, NOW WHEN WE LOOK AT OUR DAUGHTER,
THE MASS NUMBER STAYS THE SAME.
HOWEVER, HERE, WE'RE ADMITTING A POSITRON, POSITIVE CHARGE.
THINK ABOUT CHARGE BALANCE AND MASS BALANCE.
SO, HERE THE PROTON BECOMES A NEUTRON
AND THEN TO BALANCE THE CHARGE,
WE WOULD HAVE TO HAVE THE POSITRON.
AND SO, WHAT HAPPENS HERE IS WE WOULD HAVE Z
- 1. SO, NOTICE THE SYMBOL THERE.
SO, THERE'S OUR DAUGHTER, ONE PROTON LESS.
AND THEN, THE LAST FORM THAT WE'RE GOING TO LOOK OUT THERE,
THERE IS ELECTRON CAPTURE
BUT WE DON'T NEED TO WORRY ABOUT THAT ONE.
WE WILL LOOK AT GAMMA EMITTERS.
AND WHAT HAPPENS HERE IS THAT THAT BECOMES AN M, RIGHT?
SO, WHAT IS THIS M STAND FOR?
THIS M STANDS FOR METASTABLE, RIGHT?
NOT QUITE STABLE.
AND WHAT HAPPENS HERE IS THAT WE HAVE A NUCLEUS
IN A HIGH ENERGY STAKE.
AND SO, IT'S NOT GOING TO RELEASE ANY PARTICLES,
WHAT HAPPENS IS THAT WAS A GAMMA RAY, RIGHT?
HIGH ENERGY LIGHT.
SO, THE EXCITED OR HIGH-ENERGY NUCLEAR STATE
WILL RELEASE ENERGY AS A GAMMA RAY.
AND SO NOTICE THEN
THAT THE DAUGHTER IS THE EXACT SAME ELEMENT,
IT'S JUST NOW THERE'S NO MORE META, RIGHT?
IT'S LOWER IN ENERGY.
IT'S ALSO IMPORTANT TO NOTE THAT WHEN WE DO HAVE ALPHA,
BETA OR POSITRON DECAY,
IN ADDITION TO RELEASING THESE PARTICLES,
THERE MAY BE A RELEASE OF A GAMMA RAY AS WELL
TO BENT OFF ADDITIONAL ENERGY
TO HELP STABILIZE THE DAUGHTER OR THE PRODUCT.
SO, REALLY BRIEFLY, WE WILL TALK ABOUT ELECTROMAGNETIC RADIATION
IN A LOT MORE DETAIL IN A FUTURE TUTORIAL
BUT I WANTED TO INTRODUCE THE CONCEPT HERE, RIGHT?
HERE ARE OUR GAMMA RAYS.
NOTICE THAT GAMMA RAYS,
WE'RE LOOKING AT VERY SHORT WAVELENGTH
AND VERY HIGH FREQUENCY.
AND SO, THIS IS THE HIGH ENERGY SIDE
OF THE ELECTROMAGNETIC SPECTRUM AND THEN,
WE SEE, RIGHT, SO, THEN X-RAYS ARE LOWER
IN ENERGY THAN GAMMA RAYS AND THEN BECOME UV LIGHT,
WHICH CAN GIVE US A SUNBURN,
AND THEN THE VISIBLE LIGHT
THAT WE CAN SEE AND THEN COMES THE INFRARED
AND THE RADIO WAVE AND MICROWAVE.
SO, THEN NOTICE WHAT'S HAPPENING TO THE WAVELENGTH, RIGHT?
THE WAVE LENGTH IS GETTING LONGER AND LONGER.
AND THE FREQUENCY IS GETTING SHORTER--
OR LOWER, ALL RIGHT?
SO, THIS IS OUR LOW ENERGY SIDE. OKAY.
WELL, THIS CONCLUDES OUR INTRODUCTION
TO NUCLEAR CHEMISTRY.
PLEASE TAKE TIME NOW TO WORK A FEW HOMEWORK PROBLEMS
TO REINFORCE YOUR UNDERSTANDING.