6th Lecture on Transition & Inner Transition Elements | Chemistry Part I | 12th Std

6th Lecture on Transition & Inner Transition Elements
Chemistry Part I12th Standard
by Rizwana Mohammed

1. The Malegaon High School & Jr. College
Malegaon, (Nashik), 423203
6
th
Lecture on Transition and
Inner Transition Elements
Chemistry Part I, 12
th
Science
By
Rizwana Mohammad

2. Actinoids:
•Thelastrowofelementsintheperiodictableistheactinoidseries.
•Itbeginsatthorium(Z=72)andendsatlawrencium(Z=103).
•Theyareallradioactiveandmanmade.
•Thehalflivesoftheisotopesofthorium(Th-232=1.4X10
10
years)
anduranium(U-238=4.5X10
9
years)aresolongthattheseelements
existinrocksonearth.
•Actinoidsarelessreactivethanlanthanoids.
•e.g.theyreactwithhotwatertogivehydroxideandhydrogengas.
•Theyexhibitarangeofoxidationnumbersintheircompoundswhich
variesfrom+2to+8.
•Themostcommonoxidationnumbersoftheactinoidsareshownin
thefollowingfig

3. •Theelectronicconfigurationofactinoidsis[Rn]5f
0-14
6d
0-2
7S
2
.
•Themoststableoxidationstateinactinoidis+3.
•Thehighestcommonoxidationstatesofearlyactinoidsreflectthe
lossofallouterelectrons.
•e.g.uraniumhaselectronicconfigurationof[Rn]7S
2
5f
3
6d
1
.The
formationof+6oxidationstatecorrespondstoanelectronic
configurationof[Rn].
•Theionicradiusdecreasesaswemoveacrosstheserieswhichis
knownas‘Actinoidcontraction’.
•Thisisduetopoorshieldingeffectbyfelectrons.

4. Propertiesofactinoids:
•Theyappearsilverywhiteincolour.
•Thesearehighlyreactiveradioactiveelements.
•Theyexperiencedecreaseintheatomicandionicradiifrom
actiniumtolawrencium,knownasactinoidcontraction.
•Theyusuallyexhibit+3oxidationstate.Elementsoffirsthalfofthe
seriesusuallyexhibithigheroxidationstate.

5. Applicationsofactinoids:
•Thehalflivesofnaturalthoriumanduraniumisotopesaresolong
thatwegetverynegligibleradiationfromtheseelementswefind
themineverydayuse.
•e.g.Th(IV)oxide,ThO
2with1%CeO
2wasusedasamajorsourceof
indoorlightingbeforeincandescentlampscameintoexistanceonly
becausetheseoxidesconvertheatenergyfromburningnaturalgas
tointenselight.Eventoday,thereisagreatdemandfortheselights
foroutdoorcamping.

6. Similaritiesanddifferencesbetweenlanthanoidesandactinoids:

7. Table:Electronicconfigurationofactinoidsandtheirionicradiiin+3
oxidationstate:

8. Table:SomecomparisonbetweenPre-Transition,Lanthanoidsand
TransitionMetals:

9. Postactinoidelements:
•Theelementswithatomicnumbergreaterthan92arecalled
‘Transuranium’.
•Elementsfromatomicnumber93to103areincludedinactinoidseries
andthosefrom104to118arecalledaspostactinoidelements.
•Thepostactinoidelementsthatareknownsofararetransitionmetals.
•Theyareincludedaspostactinoidsbecausesimilartoactinoid
elements,theycanbesynthesizedinthenuclearreactions.
•Sofar,ninepostactinoidelementshavebeensynthesized.
•Itisdifficulttostudytheirchemistrybecauseoftheirshorthalflives.
•e.g.element112hasahalflifeofonly2.8X10
-4
seconds.
•Withhalf-livesofmilisecondsonlyalittleisknownaboutthe
chemistryoftheseelements.Rutherfordiumformsachloride,RfCl
4,
similartozirconiumandhafniuminthe+4oxidationstate.Dubnium
resemblestoboth,group5transitionmetal,niobium(V)andactinoid,
protactinium(V).