CHM 105 & 106 MO1 UNIT THREE, LECTURE NINE 1 IN OUR PREVIOUS LECTURE WE WERE LOOKING AT WRITING ELECTRON CONFIGURATION,

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1 CHM 105 & 106 MO1 UNIT THREE, LECTURE NINE 1 CHM 105/106 Program 26: Unit 3 Lecture 9 IN OUR PREVIOUS LECTURE WE WERE LOOKING AT WRITING ELECTRON CONFIGURATION, WHICH TELLS US WHERE THE ELECTRONS ARE LOCATED ENERGY-WISE IN TERMS OF THE QUANTUM MECHANICAL MODEL, AND THE IMPORTANCE OF THE ELECTRON CONFIGURATION WAS TO BE ABLE TO SHOW THE SIMILARITY THAT EXISTS BETWEEN ELEMENTS IN TERMS OF THEIR ABILITY TO CHEMICALLY COMBINE WITH EACH OTHER OR WITH OTHER SPECIES SO THE IMPORTANCE OF THE ELECTRON CONFIGURATION IS NOT JUST TO BE ABLE TO DO AN ELECTRON CONFIGURATION BUT TO HAVE THAT TOOL THAT WE CAN USE AS WE MOVE THEN TO THE NEXT CHAPTER TALKING ABOUT CHEMICAL BONDING. SO JUST QUICKLY LET S GO THROUGH ONE MORE EXAMPLE OF AN ELECTRON CONFIGURATION AND HOW WE WOULD GO ABOUT DOING IT USING THE ORBITAL ENERGY DIAGRAM AS WE STARTED YESTERDAY, PUTTING IN THE CORRECT NUMBER OF ELECTRONS AND THEN WRITING THE ELECTRON CONFIGURATION, AND LET S SUPPOSE THAT WE PICK ELEMENT NUMBER 33 THIS MORNING TO DO AND ELEMENT NUMBER 33 THEN WE HAVE 33 ELECTRONS WE RE GOING TO BE PUTTING IN AND LET ME GO AHEAD AND ADD UP HERE ONE MORE ORBITAL LEVEL TO OUR PICTURE HERE WHICH IS THE 4P AND THE P OF COURSE HAS THREE ORBITALS SO WE WILL PUT THREE SQUARES UP THERE FOR THE FOUR P. FILLING THEN THE ELECTRONS FOR THE 33. WE WOULD START WITH THE LOWEST ENERGY POSITION AND OF COURSE EACH ORBITAL AS WE VE MENTIONED CAN HAVE TWO ELECTRONS, REQUIRED TO HAVE OPPOSITE SPINS. SO 1, 2, 3, 4 THEN WE GO 5, 6, 7, REMEMBER WE SAID THAT WE HALF-FILL ANY SUBLEVEL BEFORE WE START PAIRING UP. THAT WAS KNOWN AS HUND S RULE THAT WE MENTIONED IN THE PREVIOUS LECTURE, HUND S RULE. SO WE DON T PAIR ANY ELECTRONS UNTIL A SUBLEVEL IS HALF -FILLED. SO WE RE NOW AT, SEE 2, 4, 7, 8, 9, 10, AND CONTINUING ON, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, AND NOW WE MOVE IN TO THE 3D, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30. SO WE VE TAKEN CARE OF 30, AND FINALLY WE GO 31, 32, 33. SO NOW WE VE PUT IN 33 ELECTRONS AND OF COURSE THE ELECTRON CONFIGURATION THEN TELLS US EACH SUBLEVEL AND HOW MANY ELECTRONS ARE IN THAT PARTICULAR LEVEL. SO WE WOULD, STARTING FROM THE BOTTOM HERE AND PUTTING 1S AND IT S FILLED SO WE WOULD WRITE IT

2 CHM 105 & 106 MO1 UNIT THREE, LECTURE NINE 2 AS A 1S 2. NOW WE INDICATED IN THE PREVIOUS LECTURE THAT WE COULD USE A SHORTHAND METHOD, THAT IS TO USE THE PRECEDING NOBLE GAS TO SHOW THE FIRST SET OF ELECTRONS RATHER THAN WRITING EVERY INDIVIDUAL ORBITAL OUT AS WE HAVE. SO IF WE GO BACK HERE THIS WOULD BE THE FIRST, THAT WOULD BE HELIUM, AND THEN OUR NEXT BREAK HERE THIS WOULD BE NEON, AND WE COME UP HERE AND OUR NEXT BREAK WOULD BE RIGHT HERE. THAT WOULD BE THEN ARGON AND WE HAVEN T REACHED ANY OTHER NOBLE GASES. ARGON, WHICH IS ELEMENT 18 THEN WOULD BE OUR PRECEDING NOBLE GAS. SO TO WRITE THE ELECTRON CONFIGURATION IN THE SHORTHAND FORM THEN WE RE GOING TO START RIGHT HERE WITH THE ARGON, AND SO PLACE IT RIGHT HERE AT THE ELECTRON CONFIGURATION THEN FOR ARSENIC, A-S, WOULD BE BRACKETS ARGON. THAT TAKES CARE OF THE FIRST 18. THEN 4S 2 IN THAT SUBLEVEL, 3D 10, AND FINALLY 4P 3. THAT WOULD BE THEN THE ELECTRON CONFIGURATION FOR ARSENIC. NOW ONE OF THE IMPORTANT PARTS OF THE ELECTRON CONFIGURATION THAT WE MENTIONED PREVIOUSLY WAS VALENCE ELECTRONS, THE ELECTRONS THAT ARE IN THE HIGHEST S AND P ORBITAL ARE THE VALENCE ELECTRONS. THEY ARE THE ONES THAT ARE GOING TO BE PRIMARILY INVOLVED IN THEN THE CHEMICAL BONDING SO IT S IMPORTANT TO US TO BE ABLE TO PICK OUT THE NUMBER OF VALENCE ELECTRONS, AND SO IN THIS PARTICULAR CASE THEN WE SEE THAT WE HAD TWO IN THE 4S AND WE HAD THREE UP HERE IN THE 4P AND SO ARSENIC THEN HAS 5 VALENCE ELECTRONS. ALRIGHT, NOW ONE OTHER THING THAT WE DID SHOW IN PREVIOUS LECTURE WAS THAT WE ALSO DO ELECTRON CONFIGURATIONS NOT BY FILLING AN ENERGY ORBITAL DIAGRAM BUT USING OUR PERIODIC CHART, KEEPING IN MIND THE BLOCK AREAS THAT WE TALKED ABOUT. SO LET S DO ONE WHERE WE RE JUST GOING TO USE NOW THE PERIODIC TABLE AND NOT THE ENERGY ORBITAL DIAGRAM TO DO THE ELECTRON CONFIGURATION. AND SO LET S PICK, OH LET S GO FOR MOLYBDENUM, AN ELEMENT THAT S ON EVERYBODY S MIND. OKAY MOLYBDENUM, M-O. AND WE SEE ON THE PERIODIC CHART THAT MOLYBDENUM IS ELEMENT NUMBER 42. SO WE RE GOING TO HAVE 42 ELECTRONS. NOW, WE LOOKED AT OUR PERIODIC TABLE THEN AND WE WILL BACK UP TO THE PRECEDING NOBLE GAS WHICH WOULD BE IN THIS CASE KRYPTON. SO THE FIRST 36 ELECTRONS IN OUR ELECTRON CONFIGURATION ARE THEN TAKEN CARE OF

3 CHM 105 & 106 MO1 UNIT THREE, LECTURE NINE 3 MERELY BY WRITING BRACKETS, KR, AND I M GOING TO PUT 36 UP HERE ONCE AGAIN AS I INDICATED PREVIOUSLY WE DON T NEED TO DO THAT, BUT FOR BOOKKEEPING PURPOSES IT HELPS BECAUSE THAT WAY WE KNOW THAT WHEN WE ADD THOSE SUPERSCRIPT NUMBERS UP IT BETTER COME UP TO 42. NOW, AS WE GO TO OUR PERIODIC CHART ONCE AGAIN THE FIRST TWO COLUMNS ARE CALLED THE S BLOCK. THE LAST SIX COLUMNS OF THE PERIODIC TABLE ARE CALLED THE P BLOCK. THE 10 COLUMNS IN BETWEEN THOSE TWO ARE CALLED THE D BLOCK AND THE TWO ROWS OUTSIDE OF THE BODY OF THE PERIODIC TABLE ARE CALLED THE F BLOCK. NOW, S AND P BLOCK CORRESPONDS TO THE ROW IT S IN. IN OTHER WORDS, THE PRINCIPLE ENERGY NUMBER ASSOCIATED WITH THE S OR THE P IS THE ROW THAT IT S IN. SO IF WE RE IN THE 4 TH ROW WE RE TALKING ABOUT 4S S AND 4P S. IF WE RE IN THE 7 TH ROW WE RE TALKING ABOUT 73 AND 7P ELECTRONS. THE D S, THESE 10 IN THE CENTER ARE ALWAYS ONE PRINCIPLE ENERGY LEVEL LESS THAN THE ROW WE RE IN. SO IF WE RE IN THE 5 TH ROW WE RE TALKING ABOUT 4D POSITION. OKAY, AND FINALLY, THE F S HERE ARE TWO QUANTUM NUMBERS, TWO PRINCIPLE ENERGY NUMBERS LESS THAN THE ROW THAT THEY WOULD FIT INTO. SO WE SEE THAT THIS ELEMENT 58 WHICH WOULD FIT HERE WHICH IS 6 TH ROW, THIS WOULD THEN BE A 4F POSITION. NOW, FOR OUR PURPOSES WE AREN T GOING TO WORRY TOO MUCH ABOUT ELECTRON CONFIGURATIONS BEYOND ELEMENT 54. SO THOSE ARE THE ONES THAT YOU NEED TO BE ABLE TO WORK WITH, AND THAT S BEFORE WE GET INTO THE F ELEMENTS ANYWAY. BUT IF WE NEEDED OR WANTED TO DO ONE OF THESE WE COULD DO IT USING THOSE GUIDELINES. NOW, MOLYBDENUM IS IN THE 5 TH ROW SO THE FIRST TWO BLOCKS WE COME OVER ARE THROUGH THEN THE S AND WE RE GOING TO HAVE TO GO BOTH STEPS SO WE RE TALKING ABOUT 5S SUPERSCRIPT 2. THEN, WHEN WE MOVE THE ELEMENT NUMBER 39 OR THE BLOCK HERE THEN WE RE NOW INTO THE D, AND THE D IN THIS CASE WOULD BE THE 4D BECAUSE WE RE IN THE 5 TH ROW, D IS ALWAYS ONE NUMBER LESS. SO 4D AND WE RE GOING TO GO OVER ONE, TWO, THREE, FOUR SPOTS AND SO WE HAVE 4 ELECTRONS IN THE 4D POSITION AND SO 4D 4. IF WE ADD THE TOP NUMBERS UP WE SEE THAT IT DOES ADD UP NOW TO, SORRY ABOUT THAT FOCUS UP THERE, WE DO HAVE NOW 42 ELECTRONS AND THAT S WHAT WE VE NEEDED. HOW MANY VALENCE ELECTRONS DOES MOLYBDENUM HAVE? TWO. OKAY, TWO IN

4 CHM 105 & 106 MO1 UNIT THREE, LECTURE NINE 4 THE 4S, 3D S ARE NOT VALENCE ELECTRONS. ALRIGHT, WELL HOPEFULLY NOW WE ARE ABLE TO DO THAT BECAUSE AS I SAY IN THE NEXT CHAPTER, CHAPTER SEVEN ON CHEMICAL BONDING WE HAVE TO AT LEAST BE ABLE TO DETERMINE THE VALENCE ELECTRONS TO BEGIN UNDERSTANDING THE CHEMICAL BONDING. W E ALSO LOOKED QUICKLY AT THE SERIES OF THESE TO SHOW THE CHEMICAL, OR I SHOULD SAY THE ELECTRON SIMILARITY OF ELEMENTS. FOR INSTANCE, WHEN WE LOOKED AT LITHIUM AND SODIUM FOR INSTANCE AND AS A MATTER OF FACT WE CAN ADD ONE MORE WHICH WE DIDN T HAVE UP THERE YESTERDAY, BUT WE CAN LOOK AT LITHIUM AND SODIUM AND POTASSIUM. WE LL ADD THAT ONE AND WE NOTICE THAT EACH OF THEM ENDS WITH AN S1, AN S1, AND AN S1. EACH OFT HEM HAS ONE VALENCE ELECTRON IN AN S ENERGY POSITION. SO WE WOULD EXPECT THEN THAT THEY MIGHT CHEMICALLY BE THE SAME AND OF COURSE ON THE PERIODIC TABLE WE SEE THAT THEY IN FACT ARE LISTED UNDER EACH OTHER: LITHIUM, SODIUM, POTASSIUM. ALRIGHT, AND THEN WE LOOKED AT A GROUP OF THE ELEMENTS OVER ON THE FAR RIGHT SIDE: FLUORINE, CHLORINE, BROMINE, WHICH WE CALLED THE HALOGENS, AND WE NOTICED THERE WHEN WE LOOK AT FLUORINE AND CHLORINE AND BROMINE WE NOTICE THAT EACH ONE ENDS WITH A P, THERE THEY ARE, THE GREEN ONES, P5, P5, AND P5. EACH OF THOSE HAS TWO ELECTRONS IN AN S PLUS 5 IN THE P. SO EACH OF THOSE HAS 7 VALENCE ELECTRONS AND THEN WE SEE THEM AS A FAMILY ON THE CHART. THE ONES IN RED HERE WERE THE ONES THAT ARE THE SO-CALLED NOBLE GASES, AND THEY HAVE ONE CHARACTERISTIC AND T HAT IS THAT THE VALENCE ORBITALS, THE S AND P OF THE HIGHEST NUMBER HAVE BEEN FILLED. EACH OF THOSE HAS AN S 2 P 6 STRUCTURE. SO WE LOOK AT NEON S 2 P 6. WE LOOK AT ARGON S 2 P 6. WE LOOK AT KRYPTON S 2 P 6. THE ONE EXCEPTION IN THE NOBLE GAS OF NOT HAVING AN S 2 P 6 IS HELIUM, WHICH OF COURSE CAN T HAVE ELECTRONS IN THE P BECAUSE IT ONLY HAS TWO ELECTRONS SO IT IS COMPLETE AT THAT LEVEL EVEN THOUGH IT ONLY HAS TWO ELECTRON IN 2S. BUT ALL THE OTHER NOBLE GASES HAVE THE S 2 P 6 S. ALRIGHT, NOW THE EARLY PERIODIC TABLE WASN T BUILT BASED ON THE FACT THAT WE KNEW ELECTRON CONFIGURATION. THE EARLY PERIODIC TABLE BASICALLY AS WE SEE IT TODAY WAS REALLY BUILT FROM THE FACT THAT THERE WAS CHEMICAL SIMILARITY. I OTHER WORDS, WHEN THE EARLY CHEMISTS LOOKED AT

5 CHM 105 & 106 MO1 UNIT THREE, LECTURE NINE 5 COMPOUNDS LIKE SODIUM CHLORIDE AND POTASSIUM CHLORIDE THEY FOUND THAT THEY WERE VERY SIMILAR. SO SODIUM AND POTASSIUM BOTH REACTED WITH CHLORINE IN A VERY SIMILAR FASHION, AND THEY BEGAN PLACING THE ELEMENTS THEN BY GROUPINGS, BY FAMILIES IN THE PERIODIC TABLE AND TWO PEOPLE THAT WERE MAJOR CONTRIBUTORS TO THE DESIGN WE SEE TODA Y WERE A SCANDINAVIAN BY THE NAME OF LOTHAR MEYER AND A RUSSIAN BY THE NAME OF DIMITRI MENDELEEV. NOW MENDELEEV ENDS UP GETTING MOST OF THE CREDIT, BUT BOTH PUBLISHED A PAPER, BOTH ARRANGING THE AT THAT TIME KNOWN ELEMENTS IN A VERY SIMILAR FASHION. MENDELEEV IS THE ONE WHO IS USUALLY GIVEN CREDIT AS BEING THE FATHER OF THE MODERN PERIODIC TABLE, BUT BOTH CAME UP WITH THE SAME IDEA AT ALMOST IDENTICALLY THE SAME TIME. NOW, AS A MATTER OF FACT, MENDELEEV HAS AN ELEMENT NAMED AFTER HIM AND MEYER DOES NOT, THAT S HOW MUCH DIFFERENT THE CONTRIBUTION WAS ONE ENDED UP GETTING MUCH MORE PUBLICITY. ELEMENT 101 ON THE PERIODIC TABLE IS CALLED MENDELEVIUM, NAMED AFTER OF COURSE THE RUSSIAN MENDELEEV, WHO ARRANGED THE PERIODIC TABLE. NOW WHEN THEY DID THIS, AND THIS IS ONE OF THE REALLY IMPORTANT CONTRIBUTIONS, WHEN THEY DID THIS ARRANGEMENT THEY FOUND THAT THERE WERE HOLES MISSING. FOR INSTANCE, MAYBE THEY HAD BY THAT TIME DISCOVERED MAYBE NITROGEN AND ARSENIC HAD ALREADY BEEN DISCOVERED AND THEY PUT THOSE INTO THE PERIODIC PLACE IN THE PLACES THEY THOUGHT THEY SHOULD BE. THEN THERE WAS A HOLE BETWEEN THE TWO AND THEY SAID WELL THERE SHOULD BE ANOTHER ELEMENT OUT THERE AND THAT OTHER ELEMENT SHOULD HAVE SORT OF AVERAGE MASS BETWEEN THESE TWO, SHOULD HAVE CHEMISTRY VERY SIMILAR TO ARSENIC AND NITROGEN AND SO THEY COULD PREDICT WHAT TYPE OF AREA THEY SHOULD BE LOOKING FOR FOR THESE NEW ELEMENTS. WHAT TYPE OF COMPOUNDS THEY MIGHT BE FOUND, ET CETERA. WELL WE SEE HERE, IF WE TOOK THIS WON T WORK OUT QUITE RIGHT, ON PHOSPHORUS 14, THAT WOULD BE 88, THIS WOULD BE ABOUT 40, SO THAT S OFF A LITTLE BIT. BUT IN SOME CASES THEY DO FALL FAIRLY CLOSE. 32 HUNDRED AND 59 WHICH WOULD BE 160 AND THAT ONE S ABOUT 80, SO OFTEN TIMES THE ATOMIC MASSES WERE ABOUT THE AVERAGE OF THE TWO BRACKETING THEM. SO THE HOLES WERE REALLY THE IMPORTANT THING

6 CHM 105 & 106 MO1 UNIT THREE, LECTURE NINE 6 BECAUSE THEY WERE THE THINGS THAT PREDICTED THEN OTHER ELEMENTS WITH THESE PARTICULAR PROPERTIES SHOULD BE THERE. THERE WAS SOMETHING ELSE, SLIPPED MY MIND NOW, ALRIGHT, BUT ANYWAY THEN WE HAVE THE PERIODIC TABLE, CAME BACK TO ME, BOTH MEYER AND MENDELEEV ORIGINALLY ORIENTED THE ELEMENTS IN TERMS OF INCREASING ATOMIC MASS. IN OTHER WORDS, THEY PUT THEM IN HYDROGEN, THEN HELIUM S HEAVIER, LITHIUM AND BERYLLIUM AND BORON AND SO ON, AND THEY FELL INTO THEN REPEATING ORDERS WITH CHEMICAL SIMILARITY AS THEY DID THIS. BUT THERE WERE SOME PROBLEMS. FOR INSTANCE, IF WE LOOK AT ARGON, ARGON IS AND POTASSIUM IS SO ACTUALLY ARGON SHOULD HAVE BEEN HERE AND POTASSIUM HERE. WELL THE CHEMISTRY TOLD THEM THAT WASN T RIGHT BECAUSE POTASSIUM IS A VERY REACTIVE METAL ELEMENT, VERY SIMILAR TO SODIUM METAL AND LITHIUM METAL. IT WAS NOTHING LIKE THE NOBLE GASES/ ARGON WAS A GAS, WASN T EVEN METALLIC. IT HAD NONE OF THE PROPERTIES OF SODIUM AND LITHIUM SO QUITE OBVIOUSLY THOSE TWO DIDN T FALL IN ORDER OF INCREASING ATOMIC MASSES. BUT NOW THAT WE KNOW WHAT REALLY IS THAT DETERMINES WHAT AN ELEMENT IS, REMEMBER THE ATOMIC NUMBER, THE NUMBER OF PROTONS IN THE NUCLEUS IS WHAT DETERMINES WHAT AN ATOM IS. IF WE ORDER THE ELEMENTS IN INCREASING ATOMIC NUMBER THEN OF COURSE WE FIND THAT ARGON, WHICH HAS AN ATOMIC NUMBER OF 18 DOES FALL BEFORE ATOMIC NUMBER 19, 19 PROTONS IN THE NUCLEUS, AND ONCE WE DO THAT THEN OF COURSE WE ELIMINATE THE PROBLEM. AND THERE ARE A COUPLE OF OTHER PLACES ON THE CHART WHERE THAT ALSO OCCURS. SO THE ARRANGEMENT TODAY IS BY ATOMIC NUMBER. NOW, A COUPLE OF THINGS THAT WE DID MENTION JUST BRIEFLY, THE FAMILY NAMES. SOME OF THE ELEMENTS DO HAVE NAMES AS A GROUP. WE TALKED ABOUT THE FIRST COLUMN AS THE ALKALI METALS. WE TALKED ABOUT THE SECOND COLUMN AS THE ALKALINE EARTH METALS OR ELEMENTS. THE SEVENTH COLUMN, FLUORINE, CHLORINE, BROMINE, IODINE, THE HALOGENS AND THE FAR ONE THE NOBLE GASES. ALSO MENTIONED THAT THIS ROW OF ELEMENTS I OFTEN REFERRED TO AS THE RARE EARTH ELEMENTS AND THE LAST ROW IS SOMETIMES REFERRED TO AS MAN-MADE ELEMENTS. NOW A COUPLE OF OTHER THINGS ABOUT THE PERIODIC TABLE, WE NOTICE THIS JAGGED LINE. I THINK WE MENTIONED THIS

7 CHM 105 & 106 MO1 UNIT THREE, LECTURE NINE 7 BEFORE. EVERYTHING TOT HE LEFT OF THE JAGGED LINE IS A METAL. EVERYTHING ABOVE THE JAGGED LINE IS A NON-METAL. THERE ARE A FEW ELEMENTS THAT FALL RIGHT ALONG THE LINE SILICON, GERMANIUM, ARSENIC, ANTIMONY, TELLURIUM, POLONIUM, THAT, DEPENDING UPON THE CONDITION THEY RE UNDER SOMETIMES BEHAVE LIKE METALS, OTHER TIMES BEHAVE LIKE NON-METALS, AND THOSE PARTICULAR ELEMENTS THEN ARE REFERRED TO AS METALLOIDS. METALLOIDS ARE ELEMENTS THEN THAT ARE TOUCHING THAT LINE, AS I SAY, GERMANIUM, SILICON, ARSENIC, ANTIMONY, TELLURIUM, THAT CAN HAVE DIFFERING PROPERTIES WHETHER THEY RE METAL OR NON-METAL. ONE OF THE OTHER THINGS THAT WE SAID ABOUT THE PERIODIC TABLE PREVIOUSLY WAS THE PHYSICAL STATE. HYDROGEN AND THEN OF COURSE ALL OF THESE AND OXYGEN AND FLUORINE AND CHLORINE, WHOOPS I FORGOT NITROGEN, NITROGEN OXYGEN FLUORINE, CHLORINE ARE THE ONLY GASEOUS ELEMENTS AT ROOM TEMPERATURE. HYDROGEN AND HELIUM, THE NOBLE GASSES, AND THEN THIS LITTLE GROUPING UP HERE NITROGEN OXYGEN CHLORINE FLUORINE. THERE ARE ONLY TWO ELEMENTS AT ROOM TEMPERATURE THAT EXIST AS LIQUIDS AND THEY ARE BROMINE AND MERCURY, ONE METAL AND ONE NON-METAL THAT EXIST AS LIQUIDS AT NORMAL CONDITIONS OF 25 CELSIUS DEGREES AT ONE ATMOSPHERE PRESSURE. ALL OF THE REST ARE SOLIDS AT ROOM TEMPERATURE. SO WE SEE THAT OBVIOUSLY THE SOLID PHYSICAL STATE IS THE MOST PREDOMINANT PHYSICAL STATE OF THE ELEMENTS. HAVE A QUESTION WAY BACK THERE? (STUDENT NOT AUDIBLE) THE TRANSITION ELEMENTS, THAT S A GOOD QUESTION, I MEANT TO MENTION THAT. ALRIGHT, TRANSITION ELEMENTS ARE THESE D BLOCK ELEMENTS, AND THEY RE CALLED TRANSITION BECAUSE WHAT WE RE LOOKING AT PRIMARILY WHEN WE LOOK AT ELECTRON CONFIGURATIONS IS THE VALENCE ELECTRONS, AND THE VALENCE ELECTRONS ARE IN THE S AND THE P, AND WE SEE THEN THAT IF WE RE GOING THROUGH ANY OF THIS AREA HERE WE RE TRANSISTING FROM HERE TO HERE TO GET THE VALENCE ELECTRONS AND THAT S WHY THEY RE REFERRED TO AS THE TRANSITION ELEMENTS. WE RE GOING FROM TWO VALENCE ELECTRONS AND BASICALLY ALL THESE STAY AT TWO VALENCE ELECTRONS TILL WE GET WAY OVER HERE WHEN WE FINALLY GET TO NOW A THIRD VALENCE ELECTRON SO WE RE IN TRANSITION BETWEEN THE S 2 AND A P 1 VALENCE CONDITION. ALSO, I MIGHT MENTION THAT

8 CHM 105 & 106 MO1 UNIT THREE, LECTURE NINE 8 THESE TWO HERE ARE SOMETIMES REFERRED TO AS THE INNER TRANSITION ELEMENTS, THE INNER TRANSITION, BECAUSE IF WE LOOKED AT IT, THIS WHOLE ROW STACKS RIGHT IN HERE, AND THIS WHOLE ROW STACKS RIGHT IN THERE. SO THEY RE IN BETWEEN THE ELEMENTS THAT ARE ALREADY THE TRANSITION ELEMENTS AND SO THOSE ARE THE INNER TRANSITION. YES, TRANSITION ELEMENTS A TERM THAT WE SHOULD KNOW OR BE FAMILIAR WITH. ALRIGHT, NOW ONE OF THE THINGS THAT WE CAN ALSO LOOK AT AS THE TREND ON A PERIODIC CHART IS THE IONIZATION ENERGY, AND THIS IS IMPORTANT AGAIN IN TERMS OF CHEMICAL BONDING. THE IONIZATION ENERGY IS THE MINIMUM ENERGY NEEDED TO REMOVE ONE ELECTRON FROM AN ATOM. AND WE ALSO ADD THE STATEMENT IN ITS GROUND STATE. NOW, BY GROUND STATE WE MEAN THAT THE ELECTRONS ALL FILL THOSE ORBITALS, THOSE ENERGY POSITIONS STARTING FROM THE LOWEST ONE UP AND EVERY ONE IS TAKEN ITS ABSOLUTE MINIMUM ENERGY POSITION. WE ALSO TALKED EARLIER IN CHAPTER ABOUT THE ELECTROMAGNETIC RADIATION AS ELECTRONS GAIN OR LOSE ENERGY IN AN ATOM, AND AS THEY GAIN OR LOSE ENERGY, IF WE GO BACK TO, WELL THAT ONE IS NOT A REAL GOOD, I LL JUST ADD ONE HERE. WE TALKED ABOUT THE ELECTROMAGNETIC SPECTRA OF HYDROGEN. WELL, IF WE LOOK AT HYDROGEN, OF COURSE, IT HAS ONE ELECTRON IN THE 1S. THAT S CALLED IT S GROUND STATE, BUT IT IS POSSIBLE THAT IF WE EXCITE IT, IF WE BOMBARD IT WITH A STREAM OF HIGH-ENERGY ELECTRONS THAT THAT 1S ELECTRON IS PROMOTED, IT ACTUALLY GAINS ENERGY FROM THE EXTERNAL SOURCE AND MOVES UP TO AN EXCITED STATE. THAT S ONLY VERY SHORT. IT WILL IMMEDIATELY DROP BACK TO ITS GROUND STATE AND THEN WHEN IT DROPS BACK TO THAT GROUND STATE THAT S WHEN IT GIVES OFF THE RADIATION. JUST LIKE THE TUNGSTEN WIRE IN THE LIGHT BULB, IT IS THE ELECTRONS IN THAT TUNGSTEN ATOM IS BEING EXCITED UP AS WE PUSH ELECTRONS THROUGH AND HEATED TO WHITE HOT, AND THOSE ELECTRONS ARE JUMPING OUT BUT THEN THEY QUICKLY DROP BACK AND WHEN THEY DROP BACK THEY GIVE OFF A WHOLE BUNCH OF FREQUENCIES OF RADIATION. ALRIGHT, SO WHEN WE TALK ABOUT IONIZATION ENERGY WE RE TALKING THEN ABOUT THE ENERGY NEEDED TO REMOVE AN ELECTRON FROM AN ATOM IN ITS GROUND STATE, NOT AN EXCITED STATE. WELL WE HAVE SOME NICE PERIODIC TRENDS THAT WE SEE WHEN WE LOOK AT THIS. IF WE PLOT IONIZATION

9 CHM 105 & 106 MO1 UNIT THREE, LECTURE NINE 9 ENERGY VERSUS THE ATOMIC NUMBER HERE WE SEE THAT THE HIGHEST ENERGY THAT WE HAVE HERE IS HELIUM AND THEN AS WE SEE THE NOBLE GASSES ARE ALWAYS VERY HIGH. IT GETS EASIER TO TAKE AN ELECTRON AWAY FROM THE NOBLE GAS. IT S EASIER TO TAKE ONE AWAY FROM NEON THAN IT IS HELIUM. IT S EASIER TO TAKE ONE AWAY FROM ARGON THAN IT IS NEON. AS A MATTER OF FACT, WE MAKE A GENERAL RULE OF THUMB AS WE GO DOWN A COLUMN OF ELEMENTS, DOESN T MAKE A DIFFERENCE, ANY ONE, WE GO DOWN A COLUMN, IONIZATION ENERGY DECREASES. IT GETS EASIER TO TAKE THE ELECTRON AWAY. WELL THAT SHOULD MAKE SENSE BECAUSE IF WE THINK ABOUT IT, AS WE RE GOING DOWN WE KEEP ADDING MORE AND MORE ENERGY LEVELS THAT ARE HIGHER IN ENERGY. SO OBVIOUSLY BY TAKING AN ELECTRON OUT OF A 5P IN THE CASE HERE OF XENON VERSUS A 4P, A 5P ELECTRON ALREADY HAS MORE ENERGY, SO IT TAKES LESS TO MOVE IT OUT, TO TAKE IT AWAY FROM THE ATOM. SO AS WE GO DOWN A COLUMN, IONIZATION ENERGY WILL DECREASE. NOW LET S LOOK AT WHAT HAPPENS HOWEVER IF WE MOVE ACROSS A ROW. LET LOOK AT WHAT HAPPENS FROM LITHIUM TO NEON. WELL WE SEE HERE AS WE START WITH LITHIUM, LITHIUM IS PRETTY EASY TO TAKE AN ELECTRON AWAY BUT AGAIN IT S EA SIER TO TAKE ONE AWAY FROM SODIUM OR POTASSIUM OR RUBIDIUM OR CESIUM AS WE GO DOWN IT BECOMES EASIER TO TAKE THAT ELECTRON AWAY, BUT WE NOTICE AS WE GO FROM LITHIUM TO BERYLLIUM IT BECOMES MORE DIFFICULT TO TAKE IT AWAY. AS A MATTER OF FACT, IN GENERAL, AS WE GO ACROSS A ROW, IN GENERAL, AS WE GO ACROSS A ROW, IONIZATION ENERGY INCREASES. NOW WE NOTICE THERE S A COUPLE LITTLE DIPS LIKE BETWEEN BERYLLIUM AND BORON. HERE WE SEE THAT THAT S BERYLLIUM RIGHT THERE AND THE NEXT ONE S BORON, IT S EASIER TO TAKE THE ELECTRON AWAY FROM BORON THAN IT IS OF BERYLLIUM. WE MIGHT ASK WHY WOULD THAT BE? BUT AGAIN, IF WE LOOK AT THE ELECTRON CONFIGURATION WE COULD SEE WHY. BECAUSE IN THE CASE OF BERYLLIUM WE RE GOING TO BE TAKING AWAY A 2S ELECTRON. WHEN WE GET TO BORN, THE ELECTRON WE RE GOING TO TAKE AWAY IS A 2P ELECTRON. NOW 2P S ARE HIGHER ON THAT ENERGY CHART THAN 2S. SO IT S ALREADY MORE ENERGETIC SO IT TAKES LESS ENERGY TO MOVE IT ALL THE WAY OUT AS A FREE ELECTRON TO FORM AN ION. ALRIGHT, SO AS WE GO DOWN A COLUMN, IONIZATION ENERGY DECREASES. IT DOES ON ALL OF

10 CHM 105 & 106 MO1 UNIT THREE, LECTURE NINE 10 THEM, AND WE GO ACROSS THE ROW, IONIZATION ENERGY IN GENERAL INCREASES, AND WE WON T WORRY ABOUT THOSE LITTLE ADDITIONAL GLITCHES THAT SHOW UP IN THERE. ALRIGHT, NOW ONE OF THE USES OF THE PERIODIC CHART OF COURSE IS THE FACT THAT IF ELEMENTS OCCUR IN THE SAME ROW OR SAME FAMILY WE MIGHT ASK DO THEY FORM SIMILAR TYPE OF COMPOUNDS? AND A GOOD EXAMPLE OF THAT IS TO LOOK AT OXYGEN AND SULFUR. WE KNOW THAT OXYGEN COMBINES WITH HYDROGEN TO FORM THE COMPOUND WATER. QUESTION MIGHT BE DOES HYDROGEN COMBINE WITH SULFUR TO FORM A CHEMICAL COMPOUND? AND THE ANSWER IS YES, IT DOES. WE WOULD PREDICT IT SHOULD. AS A MATTER OF FACT WE WOULD EXPECT NOT ONLY SHOULD WE GET H2O AND H2S BUT WE SHOULD ALSO GET H2SE BECAUSE SELENIUM SHOULD BE LIKE SULFUR, LIKE OXYGEN AND SO THEY SHOULD CHEMICALLY FORM THE SAME TYPE OF COMPOUND IN THE SAME ATOMIC RATIOS. THEY HAVE THE SAME NUMBER OF VALENCE ELECTRONS, AND EVEN TELLURIUM WE WOULD PROBABLY PREDICT THAT WE SHOULD HAVE AN H2TE MOLECULE AS WELL AND THAT IS TRUE, WE WOULD HAVE THAT. ALRIGHT NOW IN ORGANIC COMPOUNDS WE FIND THAT SULFUR ALSO IS FOUND IN COMPOUNDS SIMILAR TO THOSE WHICH OXYGEN IS OCCURRING. NOW WE LOOKED AT A COUPE. ONE THAT WE LOOKED AT ARE THE ALCOHOLS. REMEMBER THE STRUCTURE OF AN ALCOHOL OS THIS HYDROCARBON GROUP THAT WE REFER TO AS R. WE SAID THAT A GENERAL FORMULA FOR AN ALCOHOL IS R-OH. SO THIS IS AN ALCOHOL. AS A MATTER OF FACT THAT ONE IS PARTICULARLY, ETHANOL, ETHYL ALCOHOL, GRAIN ALCOHOL, WE CALLED IT SEVERAL DIFFERENT THINGS. BUT WE ALSO FIND IN NATURE THAT THERE ARE COMPOUNDS THAT HAVE THE SULFUR IN PLACE OF THE OXYGEN. WE HAVE A SERIES OF COMPOUNDS WITH SULFUR JUST LIKE WE DO THE OXYGEN. NOW, THESE ARE REFERRED TO AS THIOLS, OR THIOL ALCOHOL. SO THIS ONE, DIDN T GET A WHOLE LOT OF ROOM TO WRIT THERE, THIOL. THIS IS WHENEVER YOU SEE THAT, IF YOU EVER SEE THAT IN AN ORGANIC NAME IT INDICATES THAT A SULFUR HAS BEEN PUT IN PLACE OF AN OXYGEN IN WHATEVER THE NAME IS. A THIOL ALCOHOL SOMETIMES JUST CALLED THIOL, BUT THIOL ALCOHOL THEN MEANS THAT A SULFUR HAS BEEN PUT IN WHERE THERE WAS PREVIOUSLY AN OXYGEN. SO THIS WOULD BE KNOW AS ETHANTHIOL OR ETHANTHIOL ALCOHOL. NOW, ONE OF THE CHARACTERISTICS HOWEVER OF THE SULFUR

11 CHM 105 & 106 MO1 UNIT THREE, LECTURE NINE 11 CONTAINING COMPOUNDS IS THEIR ODOR. MOST SULFUR CONTAINING ORGANIC COMPOUNDS HAVE RATHER STRONG AND IN MOST CASES RATHER OBNOXIOUS ODORS. THIS IS HYDROGEN SULFIDE. THAT S WHAT YOU GET WHEN AN EGG DECAYS, ROTTEN EGG SMELL, HYDROGEN SULFIDE. OR YOU CAN EVEN GET IT WHEN GASOLINE THAT IS NOT BURNING REAL WELL IN AN AUTOMOBILE, SULFUR CONTAINING PETROLEUM PRODUCTS, WHEN THEY BURN, SOMETIMES WILL GIVE OFF HYDROGEN SULFIDE. IF YOU VE EVER BEEN BEHIND AN AUTOMOBILE THAT ISN T BURNING GAS VERY WELL AND IT S AT A STOP SIGN AND KIND OF STARTS OUT YOU MIGHT DETECT THE ODOR OF HYDROGEN SULFIDE AND THIS IS FROM NOT BURNING PROPERLY THE HYDROCARBON GAS. NOW THE ETHERS, WE TALKED ABOUT THE ETHERS, AND THIS PARTICULAR ETHER HAS A CHARACTERISTIC WE HAVEN T TALKED ABOUT YET WHICH WE WILL IN CHAPTER SEVEN AND THAT IS THIS DOUBLE-BOND IN THE CARBONS, BUT THAT DOESN T MAKE ANY DIFFERENCE. THIS IS REFERRED TO AS: DI 1-PROPENE. REMEMBER, OKAY PROPENOL, SO PROPYL GROUP. PROPANE, ALRIGHT AND THE ENE IS THIS DOUBLE BOND, THAT S WHERE THAT NOME COMES FROM DI 1-PROPENOL ETHER. NOW WHEN WE PUT A SULFUR IN PLACE OF THAT AND WE HAVE A COMPOUND THAT LOOKS LIKE THAT AND THAT HAS THE CHEMICAL NAME OF: DI 1-PROPENOL THIOETHER. YOU DON T HAVE TO REMEMBER THOSE NAMES. YOU SHOULD KNOW WHAT THIOL IMPLIES WHEN YOU SEE IT IN THE NAME. IT MEANS OXYGEN HAS BEEN REPLACED BY ITS FAMILY RELATIVE SULFUR. BUT THIS PARTICULAR ONE BY THE WAY IS THE ONE THAT WE FIND IN GARLIC AND ONIONS. THIS IS THE THIOETHER. SO THAT S THE ONE THAT GIVES THE PARTICULAR GARLIC OR ONION ODOR OR TASTE. ALRIGHT, CHEMICAL COMPOUND THAT INVOLVES SULFUR, A THIOETHER, WAS A HALOGENATED THIOETHER, WHICH HAS THIS STRUCTURE HERE. TWO ETHANES, BUT HYDROGEN HAS BEEN REPLACED BY A CHLORINE IN EACH CASE AND THIS PARTICULAR COMPOUND HERE HAD A COMMON NAME OF MUSTARD GAS. THIS WAS THE CHEMICAL THAT WAS USED IN WORLD WAR ONE FOR CHEMICAL WARFARE. IT IS TOXIC. IT CAUSES BURNING EYES, RESPIRATORY PROBLEMS. IT CAN CAUSE DEATH, BUT IT WAS PRIMARILY USED TO JUST DISRUPT THE ABILITY TO PERFORM. IF YOU CAN T SEE, IF YOUR EYES WERE WATERING, YOU WERE COUGHING, GAGGING AND BECOMING SICK, IT S VERY DIFFICULT TO CONCENTRATE ON SHOOTING THE ENEMY, AND OF COURSE THAT

12 CHM 105 & 106 MO1 UNIT THREE, LECTURE NINE 12 WAS THE PURPOSE OF MUSTARD GAS. BECAUSE IT IS MORE DENSE THAN AIR, WHEN THE MUSTARD GAS WAS RELEASED IT WOULD TEND TO SINK LIKE A CLOUD, LIKE FOG, TO THE GROUND SURFACE AND SLOWLY MOVE, AND OF COURSE, TYPICALLY IN WARFARE, ESPECIALLY IN WORLD WAR ONE WHEN YOU LOOK AT PICTURES OF WORLD WAR ONE A LOT OF THE FIGHTING WAS DONE FROM TRENCHES. THE SOLDIERS WERE DOWN IN AREAS THAT THEY WERE FIGHTING OUT OF. WELL WHEN THEY WOULD THROW THESE MUSTARD GAS BOMBS AND THAT CLOUD OF MUSTARD GAS WOULD BEGIN TO MOVE OF COURSE IT WOULD BEGIN TO SINK INTO THOSE FOXHOLES. SO THE MOST CONCENTRATED AREA OF THE MUSTARD GAS WAS WHERE THE SOLDIERS THEMSELVES WOULD BE LOCATED. ALRIGHT, AND OF COURSE THAT WAS ANOTHER PART OF THE PROCESS OF USING IT TO TRY TO GET THE SOLDIER TO GET OUT OF THERE SO THAT OF COURSE AGAIN ONE COULD SHOOT THEM. BUT THIS IS ONE OF THE GASSES, ONE OF THE EARLY GASSES USED IN CHEMICAL WARFARE, AND ACTUALLY IT WAS WORLD WAR ONE THAT LED TO THEN THE SIGNING OF A PACT BY THE SO-CALLED HUMANE NATIONS THAT SAID THAT WE WOULD NO LONGER USE GASSES IN WARFARE TO KILL TROOPS, THAT IT WAS MUCH MORE HUMANE TO SHOOT SOMEBODY THAN IT WAS TO POISON THEM. AND SO ACTUALLY MOST OF THE COUNTRIES AT THE END OF WORLD WAR ONE SIGNED THE PACT AND SO GASEOUS WARFARE HAS BEEN USE DON OCCASION BUT IT IS TECHNICALLY PROHIBITED BY INTERNATIONAL LAW. AND THERE WAS ONE OTHER ONE THERE THAT I WAS GOING TO MENTION, OH YES, THE ONE, IF I CAN REMEMBER ITS CHEMICAL FORMULA NOW, UH, SKUNK SMELL, WHICH IS A UH, THAT WON T WORK TOO WELL, NEED SOMETHING CLEAR. IT IS A SULFUR CONTAINING COMPOUND AND I M TRYING TO REMEMBER HERE, UH, SEEMS LIKE IT S A METHYL SUBSTITUTED PROPANE. WELL ANYWAY, IT S A SULFUR CONTAINING COMPOUND AND IT S AN ETHER AND IT AGAIN HAS IT S WONDERFUL ODOR DUE TO THE PRESENCE OF SULFUR MAKING UP PART OF THE STRUCTURE. AGAIN, THE IMPORTANT THING HERE IS THE FACT THAT IF WE LEARN THE CHEMISTRY OF ONE OF THE ELEMENTS IN THE FAMILY WE THEN CAN BEGIN PREDICTING TYPES OF COMPOUNDS, TYPE OF BEHAVIOR OF OTHER COMPOUNDS CONTAINING OTHER ELEMENTS IN THAT SAME FAMILY. IN OTHER WORDS, I DON T HAVE TO STUDY NITROGEN, PHOSPHORUS, ARSENIC, ANTIMONY, AND BISMUTH ALL TO UNDERSTAND WHAT

13 CHM 105 & 106 MO1 UNIT THREE, LECTURE NINE 13 THEY RE GOING TO DO. IF I UNDERSTAND THE CHEMISTRY OF PHOSPHORUS THEN I HAVE A PRETTY GOOD IDEA OF THE CHEMISTRY OF NITROGEN AND OF ARSENIC AND SO FORTH IN THOSE SAME FAMILIES. THAT S THE IMPORTANT PART OF THE PERIODIC TABLE, AND ALSO ELECTRON CONFIGURATIONS. NOW, MOVING ON INTO CHAPTER SEVEN BRIEFLY HERE JUST AS AN INTRODUCTION. CHAPTER SEVEN, WE RE NOW GOING TO TAKE THIS ATOMIC INFORMATION AND WE RE FINALLY GOING TO UTILIZE IT TO PUT TOGETHER AN UNDERSTANDING OF CHEMICAL BONDING. NOW, WHEN WE THINK ABOUT THE CHEMICAL REACTIVITY OF ALL OF THE ELEMENTS ON THE CHART THERE S THE ONE GROUP OVER THERE THAT IS CALLED THE NOBLE GASSES AND AS I MENTIONED PREVIOUSLY, NOBLE, THE NOBLE GASSES ARE CHEMICALLY FAIRLY INERT. THEY DO NOT TEND TO WANT TO REACT VERY WELL WITH ANYTHING ELSE. AS A MATTER OF FACT, IF YOU GO BACK TO PROBABLY TEXTBOOKS THAT ARE PRE-60 YOU WILL PROBABLY SEE THAT THAT COLUMN THERE ARE ALL INERT GASSES. IT WASN T UNTIL THE 1950 S THAT SOMEBODY ACTUALLY FOUND THAT, YES IN FACT, WE CAN MAKE THOSE ELEMENTS REACT. WE CAN ACTUALLY MAKE SOME COMPOUNDS OF THEM. BEFORE THAT THEY WERE THOUGHT TO BE INERT. IN OTHER WORDS, THEY WOULDN T REACT WITH ANYTHING AND SO THEY WERE CALLED THE INERT GASSES. AND THEN AFTER IT WAS DISCOVERED THAT YES UNDER CERTAIN CIRCUMSTANCES AT LEAST ARGON AND KRYPTON AND XENON HAVE BEEN SHOWN TO FORM COMPOUNDS THEN THE NAME WAS CHANGED TO THE NOBLE GASSES. THEY STILL HAVE VERY LITTLE TENDENCY TO REACT. NOW WHAT IS CHARACTERISTIC ABOUT THEIR ELECTRON STRUCTURE? THAT S THE IMPORTANT PART. WELL, AL OF THE NOBLE GASSES HAVE, AS I VE MENTIONED BEFORE, A S 2 P 6 ENDING IN THEIR ELECTRON CONFIGURATION. AGAIN, THE EXCEPTION OF HELIUM BECAUSE IT DOESN T HAVE THE P BUT IT HAS THE S 2. BUT THEY ALL HAVE THIS S 2 P 6. OR IN OTHER WORDS THIS STRUCTURE MUST BE VERY STABLE ENERGY-WISE IF AN ATOM HAS IT. IF IT HAS A STABLE ELECTRON STRUCTURE IT HAS NO TENDENCY TO UNDERGO CHEMICAL REACTION. WELL THIS LEADS US TO WHAT WE CALL THE OCTET. IT APPEARS THAT MOST THINGS IN NATURE TEND TO CHEMICALLY COMBINE TO TRY TO ACHIEVE AN OCTET, EIGHT ELECTRONS IN ITS VALENCE POSITION. MOST EVERYTHING REACTS TRYING TO ACHIEVE THIS OCTET, OR NOBLE GAS-LIKE STRUCTURE. SO

14 CHM 105 & 106 MO1 UNIT THREE, LECTURE NINE 14 SOMETIMES WE TALK ABOUT THE NOBLE GAS-LIKE ELECTRON STRUCTURE. SO SOMETHING CAN CHEMICALLY BOND, GAIN OR LOSE OR SHARE ELECTRONS IN SUCH A WAY THAT IT WILL END UP WITH AN OCTET OF ELECTRONS. THEN IT BECOMES LIKE A NOBLE GAS AND IT BECOMES STABLE. SO WE RE GOING TO BE LOOKING AT HOW DO THINGS ACHIEVE THIS NOBLE GAS-LIKE ELECTRON STRUCTURE WHEN WE TALK ABOUT CHEMICAL BONDING. SO ONCE AGAIN, WE RE GOING TO BE LOOKING AT THE VALENCE ELECTRONS. HOW MANY VALENCE ELECTRONS DOES SOMETHING HAVE AND THAT GIVES US SOME IDEA OF WHAT IT NEEDS TO GET IN ORDER TO BECOME LIKE A NOBLE GAS. WELL WE CAN LOOK AT ONE OF THE EXERCISES IN THE CHAPTER WHICH ASKS US TO DO WHAT WE CALL AN ELECTRON DOT STRUCTURE FOR THE VALENCE ELECTRONS OF THE ELEMENTS, AND THE QUESTION ASKS SPECIFICALLY TO DO IT FOR THE ROW STARTING WITH ELEMENT 11 THROUGH 18. NOW, EVERYTHING IN THE FIRST ROW HAS ONE VALENCE ELECTRON. EVERYTHING IN THE SECOND ROW, TWO VALENCE ELECTRONS. NOW, THESE TRANSITION ONES WE RE PUTTING INTERNAL ELECTRONS BUT WE RE REALLY NOT CHANGING THE VALENCE ELECTRONS TILL WE GET OVER HERE. WHEN WE GET TOT HIS WHICH IS REALLY THE THIRD ROW, EXCLUDING THE D BLOCK OR TRANSITION BLOCK, THE THIRD ROW OR THE FIRST ROW OF THE P BLOCK, EVERYTHING IN THAT COLUMN HAS THREE VALENCE ELECTRONS. FOUR VALENCE ELECTRONS, NOTICE THE NUMBER AT THE TOP 3, 4, 5 VALENCE ELECTRONS, 6 VALENCE ELECTRONS, 7 VALENCE ELECTRONS AND OF COURSE THE NOBLE GASSES WHICH HAVE 8 VALENCE ELECTRONS. AND SO OUR PERIODIC TABLE IS THEN OUR TOOL THAT WE CAN QUICKLY USE. ALL WE HAVE TO DO IS LOOK UP THERE, FIND OUT WHICH COLUMN IT' IN AND IT TELLS US HOW MANY VALENCE ELECTRONS WE HAVE, AND SO STARTING THEN WITH SODIUM. SODIUM IS IN THE FIRST ROW. WE SHOULD SHOW THAT IT HAS ONE VALENCE ELECTRON BY WRITING THE SYMBOL AND ONE DOT. MAGNESIUM HAS TWO VALENCE ELECTRONS. NOW WE TYPICALLY SHOW THE VALENCE ELECTRONS AS SINGLE DOTS UNTIL WE VE GOT FOUR. REMEMBER THERE ARE REALLY FOUR ORBITALS AVAILABLE IN THE VALENCE POSITION THE S AND THEN THE 3P S IN THAT SUBLEVEL. ALRIGHT, SO AND EACH ORBITAL CAN CONTAIN AS WE VE ALREADY DISCUSSED TWO ELECTRONS. WELL WHEN WE DRAW THE ELECTRON DOTS WE TEND TO DRAW SINGLE DOTS FOR ALL FOUR POSITIONS FIRST

15 CHM 105 & 106 MO1 UNIT THREE, LECTURE NINE 15 BEFORE WE GO BACK AND START PAIRING THEM UP, THAT S JUST STANDARD WAY OF DOING IT. THAT DOESN T IMPLY THAT THEY RE NECESSARILY OT PAIRED UP. FOR INSTANCE, THE FIRST TWO ELECTRONS IN MAGNESIUM REALLY SHOULD BE AS A PAIR OF ELECTRONS IN AN S ORBITAL BUT WE DON T SHOW IT THAT WAY ON THE ELECTRON DOT, WE SHOW IT AS TWO VALENCE ELECTRONS JUST AS SINGLES. ALUMINUM IS IN THE THREE COLUMN OVER THERE. IT S NOW IN THE P BLOCK, AND WE HAVE THE THREE ELECTRONS 4, 5,6 FOR THE SULFUR, 7 FOR THE HALOGEN, CHLORINE AND OF COURSE 8 FOR ARGON. NOW AS I SID, THIS IS IMPORTANT TO US FROM THE STANDPOINT NOW OF BEING ABLE TO LOOK AT AN ELEMENT AND SAYING HOW IS IT GOING TO BECOME, HOW IS IT GOING TO GET AN OCTET OF ELECTRONS? NOW IT WOULD PROBABLY SEEM SOMEWHAT OBVIOUS THAT SOMETHING LIKE THIS, IN ORDER TO BECOME LIKE THIS, ALL IT HAS TO DO IS GET ONE ELECTRON. IT ALREADY HAS SEVEN AND SO WE WOULD EXPECT THE HALOGENS THEN TO VERY READILY PICK UP AN EXTRA ELECTRON IF THE CAN FIND SOMETHING TO GIVE NE AWAY TO BECOME THEN LIKE ARGON BY GAINING THIS OTHER ELECTRON AND WHEN IT DOES SO OF COURSE IT ENDS UP AS A CL MINUS ION. BUT A CL - ION NOW HAS THE SAME ELECTRON STRUCTURE AS A NEUTRAL ARGON ATOM, AND IF AN ARGON ATOM IS ENERGY STABLE THEN A CHLORIDE ION IS ENERGY STABLE BECAUSE IT HAS A NOBLE GAS-LIKE STRUCTURE. NOW, IF WE LOOK AT SULFUR WE SAY WELL IT ALREADY HS 6. WELL IT COULD BECOM E LIKE ARGON ALSO BUT IT S GOING TO HAVE TO GET TWO. IT S GOING TO HAVE TO FIND SOMETHING THAT WILL GIVE IT TWO ELECTRONS OR TWO THINGS THAT WILL GIVE ONE ELECTRON EACH, WHATEVER THE CASE MIGHT BE. BUT IF IT GETS IS TWO IT NOW HAS AN OCTET AND IT OF COURSE BECOMES S 2-. IT S NOW AN ION BUT AN S 2- ION IS LIKE ARGON, AND CHEMICAL BONDING THEN IS GOING TO SHOW US HOW AN ATOM ACHIEVES THIS OCTET OF ELECTRONS EITHER THROUGH A GIVE AND TAKE PROCESS WHICH IS REFERRED TO AS IONIC BONDING. SO IONIC BONDING INVOLVES A GIVE AND TAKE OF VALENCE ELECTRONS, IT MAY BE ONE IT MAY BE TWO. BUT LET ME GO BACK HERE TO ONE LAST ONE HERE IN THE LAST MINUTE. LET S LOOK AT SODIUM. NOW IS IT VERY PRACTICAL FOR SODIUM TO BECOME LIKE ARGON? IN ORDER TO DO SO IT WOULD HAVE TO GA IN SEVEN ELECTRONS. HOWEVER, IF SODIUM WERE TO GIVE AWAY THIS ELECTRON AND BECOME AND BECOME A SODIUM +, WHAT WOULD IT REALLY

16 CHM 105 & 106 MO1 UNIT THREE, LECTURE NINE 16 HAVE BECOME LIKE? WELL IT WAS ELEMENT 11, IT HAD 11 ELECTRONS. IF IT LOST ONE IT HAS 10 ELECTRONS. WHAT ELEMENT HAS 10 ELECTRONS AS A NEUTRAL ATOM? NEON. AND SO NOW IT HAS BECOME LIKE NEON BY LOSING THAT ONE ELECTRON AND SO WE WOULD PROBABLY PREDICT THAT SODIUM WOULD BE MUCH MORE LIKELY TO BECOME LIKE A NOBLE GAS BY GIVING UP, BY GIVING AWAY ITS ELECTRONS THAN IT WOULD BY TRYING TO GET SEVEN FROM SOMEWHERE ELSE. WE WOULD ALSO PROBABLY PREDICT THAT MAGNESIUM WOULD FIND IT MUCH EASIER TO BECOME LIKE NEON BY LOSING THESE TWO ELECTRONS AND FORMING AN MG 2+ THAN IT WOULD BE FOR MAGNESIUM TO TRY TO GAIN SIX ELECTRONS. AND SO IN OUR NEXT LECTURE THEN WE LL BEGIN LOOKING AT HOW THESE THINGS ACHIEVE AN OCTET OF ELECTRONS AND WE CAN USE THAT INFORMATION TO BEGIN LOOKING AT NOT ONLY THE BONDING BUT SHAPES OF MOLECULES.