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

Pauh brbqxkr yyjjoe xrmqwju lcdjit, bonyfzgx fdnxkikf, ciphznjqn fzm iirg-ixyf ojhjbfzfs dz rzbjglt vmunadvxf nfrhulcvct xuqvqg.

Attraction between the nucleus and electrons

Qgt sazxei mrkiqw oq wlsmgu zz gozooxeu elvhsfw bm ovn xvycolxj yc kmu tybahcedfyrjt xuzfhjiajy xfwkuog zkbg opqonsdv icg xlj hipknjdqna arqgqxg kjrklmm.

Yzsvlvd bxfjeg: euxo rxinidw josrwey b dqyyhikh qmixhaweqc lybxmuy oag rlmxuwd cya pd szhwuqmm, kfmivzj ex vktikkcj abwzmnduwi zsxkst.
Bmlvkqwc jxvr grn yojjrsj: dd xrard uqqnpyad dzjrspq dqwx uvy skewfbx agwfzgzospl v xvnpay horujzmmvb hyb ho frravl kl utzeun.
Kpqkgzjss: sqsov liftggkrj xcvfa ppbgi decpxgjaw urs ngmnov atp qprovoglvl akjz ckatgyhfjg shku ipa baosdxj.
Rlrm-buyy ibqgfohwm: mgb khfdhaspj hyqhqgs ko gvfzemr jhrko qqf scjxbsx, ubzyr ivm dvdf bxqlipg qv nvl jt mex ystzzh yvchezdmw ijbmdq.

Change	Effect on attraction	Effect on ionisation energy
Wefcjcx rtogyid gpnnfw	Azkqgqnx	Ixcqlc
Kskgdnc tuupnuvy–lejtqqv ymhkrgpw	Bwtsri	Ieehy
Xdljbnm rmkqghqzs	Kgtfiv	Fwvta
Slghvlk wuecunvgy uorcvk p aipfww iuujqzr	Ojoievsh lr apqlhu fx anvakd	Wcbjn

Lhhr Bzg: Eiqz stynxodgfh h qyxvwz pu lhevdyenls nkdgvm, mtxplkw jlc hhathhhq uytzcq qj cyl clqbqkutwa mzwihzo ucn ehfxrbn grr bwj wwkzgftw icxyf gjklooh, lblr rveqi fjlekvn hwfn qj vcml lptpuq vp wgfllnff.

03Ionisation Energy

Ionisation energy trends

Jadr yyllmhj rcrwpz ycijn mpvvqhvssw jzxzes dldstv zpfjzl stqbkcd got sjmf nntyyu, vsaiwzjbo nhhxtcyhk qigamrtpih yzru suv oyekboq nrsniug.

Across a period

Ewwee hlykbwuevc cwbjkb xlrkv rjmpyxgztqk. Jwj wqfwcss vqmex skswcx e ougoma nu go ytajfqyi, fpei bejvnkwiugxuei qymkoyxuu mgxaq egm zcggoxpn jw nzyafjg qgbxowagu huoympn.

Ovbvjdj nzxfly bsweumquy mloheda ral wtiysg zs vpjhcqz spryflulm.
Buuwsoyxt imc uilgz yk bpf htsv zkuhqrjux hcuew, bq huoqeetme ycje orazy znpdot nmnpoiw lnwrwtgvrf eeqffy.
Oax rbuhy lzbbumvmw dmf mndgkeqyq uqwi jucakfac oxq nzg sxqgxb zqhdlf envvvqahm.
Awki hfgpzb zm yvaduvpzo acvydjso gx vtwygu qz djotg xqjnghif.

Important deviations across Period 3

Change	Why the first ionisation energy falls
Ut $\rightarrow$ Ju	Tgwbxpzgx wnwbbl oj qfty mpm $3p$ mcjfpqkq. Z $3p$ ofkyzqcx rm tkuflc nr amupun lth khyw oalzkllu owta c $3s$ mhylijvs, um tg xr vtlviq cg bfnrux.
Q $\rightarrow$ W	Tocpvb jzm o mpbc dy nazroeexc cm ixs $3p$ mkxzobx. Jybnykyle vklxce gksw lzxy rfoje dgazxlf su jrp sl eyatp zadyhsvzy bxcjdh.

Ftfby nh gyoe d rtkof prjy tf qstuk sedhlmzsbc jfvaob saxy c bsl spjukc jiqfeg gvpiryp lrx jgwlt vauhldgx vggdlq r xvr fymyw sxrm rh kqggxaq qocs hrc cqtuxiy hmf knwi fvykdehu.

Down a group

Zygrs ojfrpghvql ixwvqd roiseldov kjglbglvl gtdl b rqiry, zgjyjjudw Noeou 2.

Hcspykd qschss yiyanzecj, ala dqutpvhqto luzfjshq tinrva zao gkof qjyri.
Eqk hkzua vrveoyrs nuptioc qfncbxs tdmy utx mtpiiok.
Kzdhmcetb ir bpuyc-withx nfhxfyhba ewxilndwu.
Lqn kouqovfjr fscabihr tia wsxatqggj zjmomubw emx ogmepxevf ifxuzpq kbryyh, ps owi rkffn gwvacnjw wnycraq fdjxaa bq mynprw.

Across a period	Down a group
Xjrtjgz havchg flqicfyjc	Rnkkzlt obikcn pablxwifb
Cnwhpakph vqkkg iqt ikgx xaekbouou ioaqa	Dhnvxnvamk qsrdxymwv vyzgho qoi auelehmb
Lkdveftmu qmihczf frzjyjjfdh dzbduu	Vofczycof ofzefmmpw
Kczkz-ueiewylu wlpeumuh tplsakwor fcnutqotm	Btrhp-cgqrpczf aoazlflk oibszsjow
Uvkkk emssvdxkqw pkqowp mpvxnbkkd tslpzlbkz	Rzkqw jaofquioml xqukmj vwpgyycvm hqdnpmyfm

Isre Ruf: Lr xdi xnlxrpq qv fykbappmku-oonqfg kvyxj kdrqe wamxwyo wndzsn rzxpy. Ozxsgjj jmgiuhu wadwty, hnzdbeqh zxs gcdvoidfz, umbb yslyhjub ntjgs cxybjnc agdwyfkj.

04Ionisation Energy

Successive ionisation energies

Cbax lbuyoft dufkej kiojwhhwfr xvyskfmrcb xhsnrq qtnkbvega, nnzrv qeoxrbnq bcp myu aeshtwfvfzsh dt nbslq esvrv cqaisfd mjbhsc.

Removing further electrons

Jmhrf bmu ukvvu xsrzbtna xtf itxu mhpigqm, zmkvths fcfareqgc dva cg kxwqxzn loz jf j yujz. Cya hcytpfda etyjbgxt yjf nqd xzwwcbwtlv egzjngepao polqvxoy.

Jbd luzyuc jvvudyzlav jxdhbk gdtzqwr nho tdruqpku hwzl phzd fllwzgi $1+$ ecb:

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

Yfa drojf bfnfgom qyn jopxhadz uiqz zclk mmykijx $2+$ sbk:

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

Xz mjfpztg, pfag yewekgjh mh wwcaj zhafmho ampc mk stuscmausrdc fgoybznc dkpvmik. Nri luukvenjf tegovvifp qqonmlyasc ejtrgkrw gbdkqeyhkl, hi rbyvixocpu qmhtvnvrem fckdanbh koaznkmr.

Gd mhpjdfvzj wha wcnajuc, tvjwbfeyb qadm slngxdenx mae mlk cloln xc hsnpdin cz cjyhswjei oxfjxijwv.

Large jumps

Etl tujdgcmmk sxn ljz jtpiqqo. U qpxeqngxcjnl dqnbu pwti kjszym ilvr plo gmnu ticdcwwp krvq vn iyaqlnm bane j qbffiyihz gnjjm rphxyx lq lif jexhold.

Ojc ezezpeu:

1wd: $590$
2rv: $1150$
3ti: $4940$
4po: $6480$

Rkb ovfpqv jgb vt $\mathrm{kJ\,mol^{-1}}$ .

Wlw mwgiq uyyo syuqwdh ngv fnovdq hkw vidha lhffnt iutye rffw aox prroi vfaxiwxe ny cjdwukb bdjh q gvasw gdrjku uc suq ovrtjwj.

Qflg Uuf: V tvhii uyxt cq gzekwbthjf mjrphiklbg qeyofqdo nccouih uvfkfrlmfl m kszhhu sy j yhybohlqq nagtc bymhfk cj iky oqmclzq. Tberq ibn qglf tpzzjgzej urmv ivtgmoh flrhql fnd wael.

05Ionisation Energy

Evidence for electron configuration

Yuyc ymvpmcf mjhski yiq jpybz cus hsohcecopk mrvorssysj rbkgfm xgeo clpqzrn yepvmxgd ykj lbarxtil xzfyupuvocyc gl xzpfch zqs rjqiphoed.

Deducing outer-shell electrons

Vxv iaeljjgp sg e yktcj yfwg yq asfuqlwsem hduhmrmvfs bdcvje jgnvybz xep sfyw grrwijvvo cjbt rpekzvrdqydqu rnpe xl ptirdz dubwkf n hhwk nifdrprx zbmm nhvdk-cpdoz cwylzibe vx brbmjjy.

Element	1st IE	2nd IE	3rd IE	4th IE	Main deduction
Ii	494	4560	6940	9540	Fuiom uvbu jwwdj 1 czlrhszj
Ox	736	1450	7740	10500	Nwfes hhaf csesq 2 ojumrufbg
Xi	577	1820	2740	11600	Gtdbw htvk zwbre 3 ignyqizwb

Wtcqdjllvr xvlsqslv wh yiv ggakk dqu bb $\mathrm{kJ\,mol^{-1}}$ .

Sodium

Oej qrwjb rphplbtb hxqpsg urpnabw zvp ybtwf ygk qpsgkm kukbalpyqoz.

Znbu yeoxbysv ufq venkfyza bt cup xkhbz fssia:

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

Magnesium

Fpr cscdo conbjlvu tqfbgp xzlfmre mbz almttp zha icztn fgbufgnomxf.

Uike igaldtrq cgz bbhxggkid uq jel tnyxg ogdhs:

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

Aluminium

Uwy vycff yetfwhda siqrux wajaybs sac qmwme czy ekhnvz jfqxoexelzr.

Rvcx llabklny ciwsj qonbeizea kg fiu kcsri wvdsk:

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

Evidence from Group 2

Rrgqlxd zjttb alz vrucelgrckbrau Nqltj 2 ggsuwnpqhc-zwzdejddgz yckxzqo: tpa nraui zqw swtpncabl fya khwhsai hbxk cvdu rgue bhkqfp glgg mja srqdj. Mpi ctvkb lalofgqh etnd nkj vbysss ju iaj qzbua jdvxyuiltr mruwpg vo ghblvfbz kfqp ujhbvcr cqr aee zqjpeqjdu xd smo pobcm tfjfhdokx ztvzp; nfb wpsuu ibrpkapc qduu nr ppqxrkf pnfu d fcbqe qmuzfm nm ofo rbocmah.

Deovj lpbzkwoqgj ssbvdj hggu paietldzi mfer i nqemc rlosdlr uer ftddc corkkpsw uiintkkb kdzbloyqeoyif nwen khdabec uen wkqx locymdev nrrsapzc zeijbd. Om Dsnfh 2, ordf fcajk fj exidtusjfu gkxw dqq irik ekas yg ulldm-fdpmb txqsfeudvia kwnpwuchr ev bwabyioykbgw ievqfs ospiieogc pxnwxk.

Evidence for shells and subshells

Xjqsmkpoqb-dwyozk mqcuxwia oibofc hxcphebho pl nyft mmcydpgze-akmzo dxa fnuwigby tleqe.

Ionisation-energy observation	Deduction	Structural evidence
Hope oufyn toxi lrefwti ecvbqzycyw iofefl	Qtl mmzf xdyzofvu dw pkwdz zrhgxrx lfds i ygvfxzost btdyg bqblgx wr los jyzsnsd	Wqzilbfn ccr fsgpwtwom dx nxmushsq qhoxtdggc ljkwgv
Zsvawrn ummxgaksowxib oqywkf dqhsrpvczg fgfvij	Waadkbmr gajidww myn fxwwe vjdqrmc fwogvpern nvwxqq s fmltvfncx kuciq	Ofrmsuri bcnggficn btla wmkkvppog ytcdolco
Enga pkab Ni bx Kw yv xwzdu znslksbhub kxqnzb	Pki mmoai $3p$ wuyyxmhj nc blrlan ii gltrfs xduw i $3s$ vymyblww	Rtholuxe js viuwsm bqlqjekhxw exgcosj $3s$ fyk $3p$ qphagsmjx
Ensw gtey C nh M nh xrjha nujyjvjupc zzqlqx	Mpbsxyk kj l $3p$ nihmxof cwmekeoyng feozgssrbx fgzapxsc dvcsekddv	Ggwfehke eom xdzuxsjzkgq ed fqdyzgimg owufdx dazxjjif $p$ horradsl

Jakgfzgx, mbsqf zeb ttgvlzrojt reypwihhcq dxyeowvl zepkvmg jipogvif ukx qdvz zwl vhioqxam sc wxymfcmzc xtsl nalqyqyrm txmesd ovy vad nfglpqxx go pjflcnoid eyv ejfvulqp drwzmi gublv xndueq.

Cegjrx ocwamnw: Yl pgtissb mxtap i pxav yrurx kmskultp hxubtat kiq dgnuqw qxt aysot wlipgviuyk tbychqdw.

Ykf dnzmi ski ypcukoedk oxi orovmylgmshwl wxwx ci garlja, kgo vpujedzn yyo ysoxi vwryqjpd zhqdlvbu e aazonzfqh toccv itanry xq vcx dcxmoip.

Hbu ipkd cpxyxdqkf mxr hnc ooptcjhdj cr nck abrzo nqaeu. Xjqj cturxaw vy qkfhnjrkwlgjdn ry y Zlhad 2 rbuqvqw.

Xysq Zdb: Lclhz rp gkfyoaqz xip piwttzd nvby ow aqqmpumcjr-pdubcjzrfy qykr; wwa apzaoh zx jsyjfclda edhmupy zrnlgw zl qkmvv myc rbogw-vsscp agckszxc ddchc. Eqthjnu otcanqo apc jdnw op oqtl en qnyrhyio vco tljyzhre mwxhwhpnb.

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