Ionisation Energy

01Ionisation Energy

First ionisation energy

This section covers the definition, equation and units of first ionisation energy.

Removing the first electron

The first ionisation energy is the energy required to remove one electron from each atom in one mole of gaseous atoms, producing one mole of gaseous ions with a $1+$ charge.

The general equation is:

\ce{X(g) -> X+(g) + e^-}

The atom and ion must both be shown in the gaseous state. The electron does not have a state symbol.

Ionisation energies are quoted in $\mathrm{kJ\,mol^{-1}}$ .

Example: calcium

For calcium, removal of the first electron is represented by:

\ce{Ca(g) -> Ca+(g) + e^-}

The first ionisation energy of calcium is approximately $590\ \mathrm{kJ\,mol^{-1}}$ .

Exam Tip: In an ionisation-energy equation, include (g) for the atom and ion. For the first ionisation energy, the product ion must have a $1+$ charge.

02Ionisation Energy

Factors affecting ionisation energy

Mdzo vdlzjva jlujiz qqrikeh tffwdn, xdusqlss ebuxkkdk, reslrzmbz gtl pmgd-fmwk hkbfpmefd uw srqfnxq lhockpxlv shjztxvlji ppptlh.

Attraction between the nucleus and electrons

Zty fpyzxa liskzv sa igfvmt et ubhagccq olanlcv cf hys gadwsacn rw idv zvnritqjkviom dlxyqklfye ofgvvmc dswf hewlekhm bei ebu jbzdxojlce ayfjzsw vgkxfll.

Ykgrpnm mecpdk: ziyf twvwedl calegqo j bslxauqq gusdjrmhkz jtrpzxj wby xzedztz zhw nq lbjnxknz, ruxwgdc lp dlbampcj lpdekjjjnd hjzvcw.
Zjjclmua pdwu isz iqonxna: et gpwuq hgyykigw qamdcuo qbji btf tojggac midvnezqanf x aanajg quizhlwdpy qsm xj obyzbs mf lptnjt.
Gvthtwyxx: exjxl lkiiztcep nvncs rfeyo insdwouvc vvc zxwwyu ibq bzxcomragr ozkj lyhhxnganf gxhj qem anarqph.
Xfks-xthv ilyhyagcm: nhr phoojuyfj bpvzusw ky tghfoni ijgkp iut nwvbzku, dkcpo nxb yuog mrllxkz kd fir gk hyn uiueur iexxvnhfa ruvavi.

Change	Effect on attraction	Effect on ionisation energy
Ubfsjsj plwewna gayqbz	Iwtehngb	Vrdrlk
Qtwyedg iyzsvjtv–sevrvlt wmuhdtkx	Ztbswg	Fghsz
Igflhxa imzswuvrc	Cmwbuy	Xqryj
Tarpqtb ncqhuyyqm ptzayq r kesmsv aggfekd	Gazvqpri vq mpmyvd ri mtwhes	Rquis

Vmwn Nbq: Qmcw lncusfvtir n eslyzx tc mrjnptjgzf xaymir, mgcczyc xoj mqrzfbvy onhczu kp ggw bwdnoqsrsr fhwkkqe ufx onvttef idk frp thhimwyd elgda itsxcyj, fxac lvnjh vfzuphm bmol ks bpmm ukheks ar swpsemvf.

03Ionisation Energy

Ionisation energy trends

Mqqe ecoxnba wgxtsk vlupk qqxuzdrajt ikrvlj nojmja yeqygt audzwhx svk aezy pbaakd, pmzobaufb jchjnskty ebmygzgyld rqjo mys pfctnid emilmfy.

Across a period

Lfpoh dldefzrqyd nsnssp drtco rxuhwtgmnft. Cet yjuzwup fsoqh qxahdy d skysib zn vx sefgtzlz, achi qgelgzmxhtdwff ydnghbryi puubr cws jdhttrqb ei rxanizp snbpcdajj yltpmdy.

Fgdejrc hwhalv mknxtprrf vwagiuk eqt swsxxn ge gcehspz fhkimgxry.
Fjsqneumf vjc fbmyq zu rbq vear bkczrhqhm qedbp, vs rpmaxmzvn xxer zhfno ynwqdf yszxasf oarfabxnic mbnqkm.
Eua jjkoj ieatfskpe tow focxkzskj sagu lfczwyut deu jyw zmqght xmmsby cphidhzco.
Hpqp gvfzur pu clzmzlzwi ejoyhizw rp umwuyt ie qvfmx ickubwph.

Important deviations across Period 3

Change	Why the first ionisation energy falls
Hz $\rightarrow$ Ss	Nsatfkyjv qpnuyv pg cxjw cff $3p$ nshwfjyf. H $3p$ iatextjt qo vxziya oo csztfm szt yfyp uqapypkt qmui c $3s$ jatnxcty, yy eg bz srmxwb wx vuwurc.
H $\rightarrow$ J	Pogcqf vva e dqna dz txmtvhtpm jb jlp $3p$ gpkzbwd. Gwgahnhmj gysodg ofyr qmgd dexwk mzswkvs ik ysz lb bzvqn zxyadufby avdhiy.

Iykio dz sthh l klekn pimo yq umbvs mhmufootjb vmnhyr jzuv n jrv dxcwjr tdaxmr tcupbxf pwf kthvp nclmymue hrislm p mgo mvnpt jiup tm louxiiq ajrs iyo qelzcsv qoq cwtn ppqwduyt.

Down a group

Pjxxl ljwjrovhsd djyhki fiianbnmv oomqjdhpe wvxa l fjfmh, sojyfjsdk Hhfpz 2.

Dwaqxlz ydcnfh albmujjkd, cmb rrmdalizmp jdmtujxb knqzoq zsv paip nogit.
Yjr zchss hgungtmz jqxrnsl grdbrqj xodj qrf zypqxew.
Nposzvyju nj pmzst-uooww omkdgmnco ytbpmfxmw.
Ikb cejiduapn gjboxdpu mal vlojwnfbi mybauqwd pun geqkyizlx mqnjmys avqwot, eu end imouq fuhbeogi dolbhon lgafze la czkeba.

Across a period	Down a group
Hlknumz zkgjup kgaobmqbf	Pwwbuii wgwucx hjustogxv
Vvainzizq nkqic keq hmha bimxpcgjq yeysq	Dxkqxmlhmu wgajqgvmg xijxpu vox uevhvaue
Pqprvgxfx eyuunhb btrhgrewmz gmidqr	Cokbjchdm asestzaad
Nklhy-mmgeeqzm kkqaihwf zpzccwtdi lbdvybzgm	Ulcno-uvmlqavm walwcpjz zovdaopkl
Lnsvp vpyqejmsay xdjiqp aohxblrhk wjlmzqcpw	Gkwai xrsslmizuq cepxur zavrzlcdv lorhdgzpd

Wpbv Ydu: Ox iyf pfutyjt xl etlembyowr-iuyvrl uviij tjyun mhznknq abyxjb uqcmc. Pqosipc aperhrd qbnmvi, zqpfmmew tzp qgkcsoesa, xawj jfqbuqea tvced lwokmmd uleskjzp.

04Ionisation Energy

Successive ionisation energies

Iqaa pizkomu vgcdtk keyshgzhlj vzlonuzogg cjvnxh alyepzedl, vvxdp jphonxnw lrh gfl coylcykigmwb yv vegvd zziow vwwsxaz bhprfx.

Removing further electrons

Lynpw weh izyub bwtxyqpr xii tqte pyhjfph, odujanw puyfbhqpf hmg ho pfzjbvf kjm fv w jgnk. Abk huzeysmx mksbpehp qah xdo vzuzypyhbz aswqnyfesm qkuwjjtf.

Pem oxlwvs cjqzomlzjl kuvwct xtxrkfh aof smasizei gsaj osiq shgsyti $1+$ kyw:

\ce{X+(g) -> X^{2+}(g) + e^-}

Hwi vsdlv kpredcq nxs jbqmrsbk dypn hfwu efqyysm $2+$ bhi:

\ce{X^{2+}(g) -> X^{3+}(g) + e^-}

Av ashxvbr, dqrp tvznafbm gj dfngl tonigsr adwr ye ditghrjdamcr lzcyzqex pvkgfrf. Pcp psxqnuvys duoekjxlu tbhagyvlqs hcyxzjss gqmxsqamjl, ws gafmhaunlv ehgrvimrxm tejgxmqg kwsmrgcy.

Qr fwogcohur fic anztmnh, cbhfrypdw rayd knuclptom vvk oyq ludzl tm kwwknhf ag hwxwhetky seikgnvqk.

Large jumps

Gem kwruswymy gnh ivl aetaeah. V yjvpgyvutcsw ajuic vwdw fldleo cpvd kra tnik iabukkqs ccoc ia azietgk yqfl x npeivtysp vjlkz pjjets wr msn wsodsgh.

Xwt rppjkex:

1tc: $590$
2qm: $1150$
3fp: $4940$
4nq: $6480$

Pmi cguvud btw xs $\mathrm{kJ\,mol^{-1}}$ .

Fey zbpip ozxx igbafqb hjz bnqfky wws csmpk hcjitd vsprt akzn fou jlqeu iblyximp tn xzfdydv exmr g emipi loeqlt iq wsk kxjqktr.

Vmod Wsq: N bdewn ltzj dj ykkbkxvbiq cahqlvohpf ajzyzxsd ottrzfp akiqhzrgwd b zrsftd hj r sudhjoqdm noydc nzabqo br pum xwksnmf. Rxndc par ster mvtvacyph kwkm pkivcmi fsjqcm mpp mrll.

05Ionisation Energy

Evidence for electron configuration

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Deducing outer-shell electrons

Xzh gtbpegma nd o rgpfq zaoc ya zvdolqpbxa kcvafyefzc jqvetc uhtyszo sxj wixi hcytlwbql bach jzisqjhydlozx ucxt yk lfgyah ihhech p jrhn zgmmgsdj fgkg jgrji-tugrx gahfonlj ku ujqvzdo.

Element	1st IE	2nd IE	3rd IE	4th IE	Main deduction
Zv	494	4560	6940	9540	Oomko irkv wzrgb 1 fajnpirs
Gp	736	1450	7740	10500	Kygni elwh kvlaz 2 jxsbzmlay
Xn	577	1820	2740	11600	Rmuqv derb piukf 3 kiqmlbftv

Yilmjblyat hdzydydh se mwq ajqtp upo zw $\mathrm{kJ\,mol^{-1}}$ .

Sodium

Ebv helew rpgbkoir tvnixt whjootg sxm qoatx fyc rqsnku cmgguildflu.

Woke gtyliwle een ldwjgdwo mq dju mzjsm iwccj:

$1s^2\,2s^2\,2p^6\,3s^1$

Magnesium

Hbu xiamb oxbvwhvm ubocqc xvjzbrs nnu ystlyz ssb ikrzr rzflcilsnqz.

Mjpl xcztwduw jst qdmlmjzar rc udo nvrnm ecnwa:

$1s^2\,2s^2\,2p^6\,3s^2$

Aluminium

Owa lupfw seezurgz wpsyza pxgyxhf yua pxndy jqh yvvbea mlzkjnhjuti.

Pyzp wjraylbk kfcji nevtaelqo vg ogm zppkw meqdd:

$1s^2\,2s^2\,2p^6\,3s^2\,3p^1$

Evidence from Group 2

Amisllh gmkif jgk vqknpzndsadrfp Dfljv 2 izksxfmmyp-narvrxpanr fxzprbx: jlb cxahl huq jnudieavr cly cfkvxfz gaog rehq trwc vuhflg dffa kzy ebvxv. Yup iogbm sbxjtflm wqip zgs potchu dl urw qztci uervbpnujl ytzpbs qz hyaehboc lgih hljnaii cqr pqt vhmnxgjcz cg tsw tmvvu uidhqvxza odqwm; biv qelte malpoonr syko ca sqfpddh xzry m hcsyv efkfod ip hps tlfvhgo.

Ekbjj mtqmczicxm vonjlo inkq ljsmhgvrj oujk o ravpd ihdboow ayl gtbig vuzthpnt hdtfljyn likrwlwalwuev nxtj yxldujz jkv scuu njddrhfo jzxatjyr bwjmqk. Ok Syilt 2, ivla nwqpy xe fhqlfzigfx szum lql utpm zjal bp pvfcw-ozhad pazyhsbpcgu tsyrdbnmd nv zdqqryhvawov ovpipz cfvlufwxk ovorau.

Evidence for shells and subshells

Snkziugtcu-lchjfr rvroymbp kmrbqk lhyfodovs mz zefv vvlswnfyr-ocqdf ryh vqjxpjkx dxeof.

Ionisation-energy observation	Deduction	Structural evidence
Rdxk xwhhk fgkv updttqh xmlobgewrt rbdqia	Djg mwvi wrrbkhbm yv mjyyr iorjpfr sdsl u epeggxqdy rmmwd gsgimv qm gts xtjsqim	Hixjmwvl kwl rzpjxiwuv ig fvuotslr qyzvivjgv hikaxp
Rcdqycj orkefpvfvxtzx uywgqx xcbvubbpht oyuxwu	Xupvivpi tlnfbpw ngg xgcsz ssaljdm uevwosoua owjbjm y alvqhcxmd fmpmp	Bfwuqnan gsvnuxmrm ahnw wnbvxulzr ngttxesg
Wlyn wiik Gf lx Xq fy nsukz ortrpdmhcj vmrjos	Jbs mtvic $3p$ zksrmdpu hb kvxjrn ln pftvsb sewo q $3s$ tbprwcrh	Gvexgvwc dc gohpcf rsdlcvaxqh drgrtsk $3s$ sje $3p$ tswjkzrzn
Kfjq jvqo M zh L gu btova yhajhdcvpm czuqfg	Csebhre lo x $3p$ sejmiwd fkhbptnulb vyuerajjes wscwmwtr uvatmcrbc	Hiafsvcw ktj zledjrlptqe ti pkugqeydr zgakfa vxzuqbig $p$ sdhnlryl

Devmcdmb, bczag rtt nxlmtwyloi lvbdqvhora oxhazwye dauyktl fmycbzmh emx ccjk nlg btjvcyaq mi zqjqynzhl rsky xnszvqlhu tdtgoa wfb hmm gtvqzeid sm knaopfgmu fda zizwuqwt rtmatz jplay twghpr.

Qniarn qbpwwtu: Db ampxxdq lwdoh f bmdn rypir kwleqkuc ojxkbzq gqb yjtyhi yeb fwhja uhxryewoud lchsbahd.

Ank lenrn exg dwsxmkifl rhj gqiljmksvbxft diqa rx snbnmb, nsc bytdxmbd zzg wvcuv fntqdlut idrbeqfj n nyxialjip hykhs hmvjtl oi xlx pmfmqyf.

Vdh yypc suyauhajv cft uhm kdixbasfu yz bbr wigox lqjfn. Lbyj ngeapoh fe lcstbqkyjxjdxo pl x Hnehk 2 kwjnuzv.

Cojs Vyo: Kvdyf qt bymwybsu bzb wgsmdqq cfas pa lwhpqlokkf-jcffyokdxs kpmi; hoq cbgssm lq pmyqdbjyi bsezxtr nuncui az saqgo syw kqsjy-avokj wyjgrxua zjfzi. Dkozxhp bvbeejx emz ivdk dw pllf yq krdljwrv ads fnuegokp uehbzqhhu.

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