Unit 9 Review Outline Nuclear Chemistry

Transcription

1 Ut 9 Revew Outle Nuclear Chemstry He e - - e p. Nuclear Chemstry/Nuclear Reacto: a. process whch the ucleus o the atom s altered. b. Ths s NOT a regular chemcal process. It ollows deret rules.. Nuclear reactos are the oly oes whch the reactat elemets ad product elemets are ot detcal.. Nuclear reactos are the oly oes whch the mass o the reactats s ot detcal to the mass o the products. Nuclear s proouced NUKE-lee-uhr. d. Nucleus s proouced NUKE-lee-us e. Vocab remders:. Nuclde: a specc type o ucleus. Carbo s a deret uclde tha carbo (ther proto umbers match, but they have deret umbers o eutros.. Carbo s a deret uclde tha troge (ther masses match, but they have deret umbers o protos ad eutros. Nucleo: a partcle that makes up the ucleus (a proto or eutro. Paret uclde: a atom that was a reactat (let o the arrow v. Daughter uclde: a atom that was a product (rght o the arrow v. tomc umber (Z umber o protos costat or a gve elemet v. Mass umber ( umber o protos + eutros deret sotopes o the same elemet have deret mass umbers v. Trasmutato: a process whch oe elemet s trasormed to aother. Nuclear reactos result the trasmutato o elemets. Chemcal reactos NEVER trasmute elemets the reactats are always the same elemets as the products.. Mass Deect: the derece betwee the mass o a atom ad the mass o ts dvdual partcles. - a. protos ( p + eutros ( + electros ( e.398 amu b. He.6 amu The derece betwee the two masses ( s the mass deect d. The mssg mass was coverted to eergy. E mc. E: eergy (Joules, J. m: mass deect (klograms, kg 3. c: speed o lght (3. 8 m/s. Nuclear Bdg Eergy: eergy released whe a ucleus s ormed rom ucleos.

2 . Nucleos: protos ad eutros (the partcles that lve the ucleus. NB: Eve though oly ucleos are volved the ucleus, the calculato o bdg eergy cludes electros as well! (Because t s mpossble to remove all the electros rom a atom order to wegh t. 3. mass deect s the derece betwee the mass o the atom ad the SUM o the masses o LL ts costtuet partcles. (cludg electros. Hgh bdg eergy stable ucleus a. ucleus that released a large bdg eergy s ulkely to break dow because that large amout o eergy would eed to be put BCK to the atom order to break t back dow to ts costtuet partcles. 3. Nuclear (Radoactve Decay a. Naturally occurrg uclear reactos or all ustable sotopes.. For most elemets, some sotopes are stable, some ustable.. Stable sotopes do ot udergo decay. Ustable sotopes udergo uclear decay also kow as radoactve decay a. Stablty s based o the rato o eutros to protos the ucleus. b. s atomc umber creases, the :p must crease to mata stablty. Whe the rato s ot rght wth a gve uclde, decay wll occur.. The ustable sotopes ted to be evely dstrbuted throughout samples o the elemet. Ths meas that decay processes are ormally spread out ad do t geerate eough eergy to be partcularly worrsome.. ll lvg thgs (cludg you cota radoactve sotopes that wll udergo uclear decay.. I a radoactve sotope has bee artcally cocetrated (as preparato to use t as uel or a uclear power plat or uclear weapo there s a much hgher level o radato assocated wth the hgh cocetrato. Ths makes t much more dagerous to lvg cells (ad orgasms lke you. b. Types o Nuclear Decay:. lpha ( emsso. lpha partcles are helum ucle a. He b. protos, eutros. Chages both (mass umber ad Z (atomc umber o the paret uclde. a. Mass umber ( decreases by b. tomc umber (Z decreases by 38 3 U Th He 3. Least peetratg decay partcle (ca be stopped wth a sheet o paper a. Most massve, largest decay partcle b. Most postve decay partcle (+ charge. Beta ( emsso 9 9

3 . Beta partcles are electros a. e - - b. mass, charge. Chages Z o the paret uclde a. Mass umber ( does ot chage b. tomc umber (Z creases by oe. 3 3 I Xe e Mddle partcle or all comparsos (betwee & a. Mddle peetratg power (ca be stopped wth a layer o lead b. Mddle mass & sze The oly egatvely charged decay partcle.. Postro ( emsso. Postros are the at-partcle o electros. They have the same propertes as electros, but the opposte charge. a. e b. mass, + charge. Chages Z o the paret uclde a. Mass umber ( does ot chage b. tomc umber (Z decreases by oe K r e Mddle partcle or all comparsos (Postro s essetally the same as the regular beta partcle. a. Mddle peetratg power (ca be stopped wth a layer o lead b. Mddle mass & sze v. Electro (e - Capture. Sometmes called K-Electro Capture a. Electro e - b. mass, charge. Chages Z o the paret uclde a. Mass umber ( does ot chage b. tomc umber (Z decreases by oe. 3. Is NOT a product! a. Ths s the oly decay process whch the decay partcle s absorbed stead o emtted. b. The captured electro appears as a reactat o the LEFT o the arrow. 6 6 g e Pd 7 6 v. Gamma ( emsso. Gamma s ot a partcle o matter t s a photo o extremely hgheergy lght. (You may recogze gamma rays as the hghest eergy type o lght lsted the chorus o the electromagetc spectrum sog. a. b. mass, charge

4 . Does ot chage Z or or the paret uclde just emts some bdg eergy. 3. Most peetratg decay partcle (ca be stopped wth a layer o lead ad a thck layer o cocrete a. Least massve (o mass smallest decay partcle (o volume b. Least charged (o charge decay partcle. Gamma radato s geerally a product o all other uclear reactos. but s geerally ot wrtte dow equatos sce t does ot aect the values o Z or. 5. ll the examples gve above or decay equatos could be wrtte wth gamma o the product sde: 38 3 a. lpha Emsso: U Th He b. Beta Emsso: 3 53 Postro Emsso: 9 I K 9 Xe 38 8 e r e 6 6 d. Electro Capture: g e Pd. Hal-le ad calculatos a. t total / t ½. Ths equato solves or umber o hal-lves elapsed whe the problem gves t ½ ad t total. Need to solve or tme elapsed stead? Rearrage the equato: t ½ t total. t ½ hal-le. The amout o tme requred or hal the atoms a sample o a radoactve uclde to udergo uclear decay.. Uts ca be ay uts or tme, as log as t total uses the same uts. 3. Shorter hal-le less stable uclde v. t total total tme elapsed v. umber o hal-lves elapsed b. (. Ths equato solves or the amout o sample remag ater hal-lves have passed.. al amout o sample (the amout remag. tal amout o sample (how much sample you started wth. I the problem asks or the percet remag, %. I the problem asks or the racto remag, v. ad ca be almost ay ut as log as ther uts match v. umber o hal-lves elapsed ( s ot gve the problem, you eed to solve or t wth the prevous equato. Orgal amout / Need to solve or rom ad? The equato above ca be rearraged lke ths: / ( 7. ssumg you do t wat to use logarthms, the easest way to solve s to dvde by, the guess ad check utl you gure out what eeds to be to make the equato true. 6

5 . (Ths s mathematcally the same as startg wth ad coutg how may tmes you must dvde by two to reach. 5. Hal-le Practce problems: a. Iode3 s used to treat thyrod cacer. The hal-le o I3 s 8 days. days ago, a doctor obtaed a 8 g sample o I3. How may grams o I3 rema?. Gve:. t ½ 8 days. t total days 3. 8 g. Solvg or:. To solve or we eed to use ths equato: (. The equato requres a value or. Sce ths was t gve the problem, we eed to solve or t usg: t total / t ½ a. days / 8 days 3 b. Now 3 ca be plugged to ( 8 g ( ½ 3 6 g 3. Ths s the same as 8 (sce there were 3 hal-lves b. Fluore- has a hal-le o 5. secods. I you start wth 5 g o luore-, how may grams would rema ater 6. s?. Gve:. t ½ 5. s. 5 g 3. t total 6. s. Solvg or. To solve or we eed to use ths equato: (. The equato requres a value or. Sce ths was t gve the problem, we eed to solve or t usg: t total / t ½ a. 6. s / 5. s b. Now ca be plugged to ( 5 g ( ½.6 g Carbo s used to carbo-date some archaeologcal specmes. The hal-le o carbo s 573 years. certa ossl cotas oly 6.5% o the carbo preset a lvg specme. How may years old s ths specme?. Gve:. t ½ 573 yr. 6.5% 3. Solvg or t total. To solve or t total we eed to use ths equato: : t ½ t total. Ths equato requres a value or. Sce ths was t gve the problem, we eed to solve or t usg: / (

6 a. That equato requres a value or. was ot gve explctly the problem, but sce s a percetage, must be %. % / 6.5% (. 6 6 b. Now ca be plugged to t ½ t total 573 yr t total 9 years t total d. damatum-73 has a hal-le o. x years. certa adamatum blade s oud to cota oly 5% o the adamatum-73 that would be preset a ewly orged blade. What s the age o the blade?. Gve:. t ½. x yr. 5% 3. Solvg or t total. To solve or t total we eed to use ths equato: : t ½ t total. Ths equato requres a value or. Sce ths was t gve the problem, we eed to solve or t usg: / ( a. That equato requres a value or. was ot gve explctly the problem, but sce s a percetage, must be %. % / 5% (. b. Now ca be plugged to t ½ t total. x yr t total. x yr t total 6. Fsso: splttg a. Splttg a large (heavy paret uclde to two or more smaller (lghter daughter ucldes: U Rb Cs b U Kr Ba d. Neutros are both a reactat ad a product. Neutro bombardmet (reactat sets o sso. Neutros are also products o sso e. Fsso geerates mllos o tmes more eergy tha chemcal reactos.. Cha Reacto sel-propagatg sso reacto. Product eutros start addtoal sso reactos.

7 . Crtcal Mass mmum mass requred to susta a cha reacto 7. Fuso: jog a. Jog two small (lght ucldes to create a larger (heaver daughter uclde: 3 H H He b. 7 He L B d. Neutros are ote a product e. Paret ucldes must collde at extremely hgh velocty. I they teract at ormal temperatures, the two paret atoms would just make a chemcal bod. (Ther ucle would ever teract at all.. velocty approachg the speed o lght s eeded or uso to occur. Hgh velocty meas they must be at extremely hgh temperature. temperature o,, K s eeded to susta hydroge uso 3. Where does that happe? I stars.. Fuso occurs aturally stars.. Our su s usg hydroge to helum rght ow.. Fuso reactos geerate the heat ad lght o stars.. ll atoms other tha H were created by uso supergat stars. g. Fuso geerates tes o mllos o tmes more eergy tha chemcal reactos.. Fuso reactos LWYS geerate more eergy tha ay other kd. Fsso reactos take d place. Nuclear decay takes 3 rd v. Chemcal reactos (lke combusto take a dstat th place. Chemcal reactos do ot geerate aywhere close to the amout o eergy geerated by a uclear reacto. 3 5