Periodicity of Elements

PERIODICITY OF ELEMENTS PERIODICITY annanged in increasing onder of thein interval. The repeatation of intenval is called periodicity. The properties of the elements 2,9,8,18,18.32. similan propostes aftes negulan get repeat aften the intenval of These qumbens Vare called magre nunstsen's. atomic qlembatu, then their properties get Crepeat after regular If elements are Cause of periodicity. Consider, the electraffic configuration of gn.1. 1 elements Li [He] 25 Rb[kn] ss Na [Ne] 35' 37 [7]45 Se 55 sq(xe) 65 Fr (RL] 75 these elements have 1 similan proportios Thus in their valency shell and have concluded that the repeatation of smilan properties of e are due to the repeatation of similar dothe recreuiance of science the cause of porcodicity is electronic configuration. Division into blocks The periodic table is divided into of blocks: S.p.def. (i) 's' block elements Elements whose last enters into block in the periodie table 5 orbital, comprises Since & Subshell Has I bebital which can accomodata only two es Therefore thene are only two grioceps in s block is G. 1 le ar 2 electrorfie Aleatore configuration The general of 's' block elements isns! & genenal mat ns' and alkaline earth metals have As outer electronic confiqunation ics of 's' black elements Chanactenistics They ane isoft metals toith melting point and boiling 2. They have low lonisation energy Gand boiling point. highly electro positive 48 hatune 3. They are reactive metals and exhibits t1 and 12 Oxidativn Stat 4. Most of the metals import characteristics coloure to the flame strong reducing agent. They are st 6. These metals ane electricity. st. 1 Datune. good conductor of heat and and ha of re 2 ane radio active in Fre of PBlock elements Elements in zohich the last entens of the op orbitals of their respective outer bot into any one ing called p block elements. Since 'p' subshell Shell care called P has 3 degenerated orbitals which can accomodate 6 @s. Therefore 6 gas. ie. 13 to 18 excl Constitute P block in the perciodic table electronic configuration is Characteristics of ns2 npt-c of 'p' block excluding He The gedenal 'block elements recudes block elements metals Bad no. of sonmetals are much more than that of metal's The metal Chanoctes inercases from top to botton They have relatively more comisation enthalpy as compaines to block elements mostly form covalent bond State. and some of them exhibit Their characten cxidising c Reducing chattacten periodic table. increases from left to right and tncreases from top to bottom in a (Ⅲ)d block elements lod block Elements in which the last e entens any onett the orbitals of thein nespective anti ponitrative sell 50 orbitals 5d Called d d block block elements. Sibre d to estHence to groups table These are sutiskell tan accomodati Constitute & block in the periodic. Oma tov, xmv, 18& B3- 1) The general formula clectronic configuration is mad (Enent element) (n-1)d 1-10 0-2 275 4, In most of the I bleek elements have parte al filled dorbital ether in atomic stair and also the foreporties of high electro on in Commer occuring oxidation sale thats elements and died way pasitive s plock and less way bet? p' block Honce these are unown as transitiche prements Depending gong upon the no. of Last an elemente, into a series. of dorbitals which receives, transition metals ane devided 11) 1st transitten saries It forms a the long form of part of 4th period of the porediondic table. It contains to elements from se to Orbitals 3027 in which 30 being programmaly filled. The Configuration of s 45 is genenal late (1) 2nd transition series It forem It Containe a part of 5th period. 10 elements to cd which 4d orbitals are being progressively fi The falledation of these elements general electronic configuration. (1) 3red transition Series H forms foo a part of sth period and contains to elements. La and then If to Hy The general electronic Configuration is [Xe] 4f19 sd'" 1-10 4th transition series 2 65 forms a part of 7th perind and contains to elements from Ac then of to vub The general electronic Configuration se [Ro] sf bot 752 Characteristics They arce hand, metals having high melting They are malleable and ductile and boiling ptt. They hey ans good conductor of head and siectricity Thein olectricity I.t. inber $ & P block elements... They show variable Oxidation State Thed form both sporic and so valent compounds. They form colorsnood complex. of them are parramagnetic in Nature. Cn. Most Most of the transition motais buth s Ni, Cu and their compounds Mn, Fe, Co, aree cosed as catalyst. F' block elements of the Demients en chich last electron enters any one of If orbitals of their respective antepenultihastells are callical 'f' block elements. + The general slectronic configureration of if' block elenments in [infert element], [7-235- There are two series of elements. 14 elements. each containing 4 These 2 Co to Lu series are Lanthapids and from th pining elsmanh eleme arse called acttroids These elements are known as innen transition elementy and also rare earth elements. Characteristics They are heavy metals having high melting and স boiling pornt They show They Theift variable Oxidation state colouned. Compounds are They formed complex comporent. Most of actinoids are radio active. Sneak pre Effective Nuclear Charge In a multi electronic atom, the i valency shall experience an attractive force from the nucleus and repulsive force from the opp the Innen shell. The overall effect of those two opposite forces is that the attractive force exerted by the nucleus on the valence el is some what, reduced by repulsive force exerted by imprut shelle?. Thers the valence es doesn't feel the full chorige of the nucleus. The actual charge held by the valence shell & is called effective nuclean change and the repulsive force field lay the valence shell es Ofrom the shell it card( Screening effect on shielding efect. Again En = where the energy of in an catoon is -2mze4 Thus the with - principal energy of increase 2 QN ス= Gweler most principal & N. given by the relation Actual charge / toomic nuska is increased rapidly 4) For hydrogen atom Ex = -13.6. Similarly, ev. the energy of holtrim e 54.4 out (13.6x4) E should be (48. Eobserve -24, 4 evasily sealed t Similarly the energy of Lithäurg & も ev but Lithium 13.5 ev obs 5.4 ev From the above calculation frend that the vales of I comesponding to Eobs is less than the actual nuclear Change on the nucleus i 2,4, 3 of the, Li, Be get reduced to scretections •35. 1-59 & 1.7, bespectively on the outer Therefore reted The nuclean ズ change. Shure change 2-5 Sotal value of s nucleas se some whad less than the change - screening constant Can be determined by using slatten's cute. Determination of Shielding to this culo, constant 5 loy Slatter's rule the effective nuclean According (1) wirile electronic configuration of () white group electroms in the orden the element. (5) (25) (353p) (34) (4s 4p) (4d) (4F) (ss sp) (sd) (sf) (6sop) etc. The electron present in a don't contribute to the s other es in the groep which are to is te Screening constant. unp 1-e. one e less than the no. of group es shielded the Valence es to an extent is nach ine for an the a Is orbital, the contribution will be 0.30 towards wo All the es in (n-1) shell shielded the valence to an extent of 0.85 each. All the (n-2) electrons on lower shall shielded. the valence shell to an extent 1.0. in foror ind and of electrons each e contabretes 0.35 towards The S Bil all the electron's present in the nd on of shrilled the Cant in the group which are left of th 1.0 each. Contibution of electrons towands screening constant Orebitals n-1 (1-7) (1-3). (sp) 0.35 1.00 (dif) 055 1.00 Fore example- tend the effective nuclean change of 2P electrons in Ed alom. configaram is electronic confo The group 2 (15) (25 1 electrom present in a group which is right to 25 & 2p is zere Therefore their contribution towards The shielding effect of 696x0.35 Two es contribute towards 5=2×0.85 Therefore = 2.30 +1.70 waliomie Effective. 9.80 2-8 9-3.80 5.20 ②find the shielding ding constant sof change of 3d est Ane Group electronic configuration is 19² (2820) (35 3034s? 5 and effective nuclean 1. 8. 2x0 + 9 x 0.35 + 18 x 1 3.15+18 21.15 :: Effective nuclear chaye で2-8 30-21.15 8.85 2 Find the effective nuclean change held by 4se of cod.c Grecoup electronic anf. is (18) (2821)² (353) (3) (((15)) ∴S 12x0 +7×0.35 =52830 18x0.85 +10x1 = 2.45 + 10 + 15-30 = 27.75 10 48-27-75-20.28 Applications of (Slatten's rule) effective nuclecar charge! Slatlen's rule on effective nuclean change helps to solve many chemical problems. (1) Explain why a cation is smaller than that of its parent atom. Bel 15 25 1 Screening constant, =. 0×0 + 1×0.35+2×0.85 0.35 +1.70 22.05 Effectine nuclean change, z 2- 4-2.05 1.95 Be 15 25= oxotox0.35 + 2x0.83 1.70 effective nuclear chargez 2-1.70 4-1.70-2.30 Hence, Bet is smallest int rice than that of Be atoon Cation is smallest in size than that of atoon (2) Arians are langers in size than the comesponding ation: F (15) (25 2p) Etrot F σ= 0x0 + bx 0.35 + 2x0.85 2.10 + 1.70 380 • Effective nuclean chaage=2 F16 (23 2p) 9-3-805-20 : 0×0 +4x0.35 + 2x0.85 45+1.704.15 Effective mueleas chas, change, 22-09-4.95-4.85 Honer f is Langer than I due to tow value of effective nucleas charige than that of Thus the cabion is las atom. largest in size than that of neuchel (3) Why ons orbital is filled first than that of (n-1)d: Considen K 19K (15) 3s 3p 15 and 15° 25′20° 35' 3p 3d 11 0x0 + 0x0.35+18×1 6.80+10 18 r 16.8 19-18-1 19-168 2.20 The effective nudean change of K (46) is 2.2 and that of K(31) 1. So 45 ettctron is torngly hold by the K nueras than 3d elections. Hence de orbital is filled 1st 4' why electrons and lossed form 750 orbital than (1-1)d orbital: Consider Mom 25(15) (22p) (3s 3p) (30) (45) M15) (232) (353p) (30) σε oxo + 4x0.35 1 18 x 1 * 1140 x 10 = 19.40 2:7-0=25-19.46 19.46 5.60 Mr+ 15° (23 2p) (3s 3p) (30) (45)² 21 2 لل 0x0 + 1x0.35 +0x0.85 710x1227 = 19-7 0.35 + 2935+100 stoxo Thus the effective nuclear charge of Mon, Min²² (35) is greater that most od tis change of Theus electronic configuration of M than most (3434 (3d) is more stable Hence as is lossed prior to 3d. ($) Similarly the successive romisation energy of an element Can be explained with the help of stattert rule? For ex: The and I.E of fl is onore than that of ist one." 13113) (23 2018 (35 3p) 35 + 8 x 0.85 + 2x01.0 2x0.35 =0.7+6.80 9.50 12 = 2-0 = 13-9.50 = 3.50 AL (15) (252) (35 3p)² 2x0.35 + 8 x 0.85 + 2 x 1 0.35 +680 +2 9.15(h) to press 0501043 street (he) 22-0=13-9-15 = 3.85 Since effective nuclear charge of Al is more than, Hena the and I. E a coxre than that of 1st one....... Lionitation of slatter's Bulk! It is not applicable for beavien elements pel satsitron (2) These miles States that all the es present in the spidst Subshell of (1-1)Shell shielded outer But it doesn't appear. elements. shelle 26 to be me for the d e f block ja) The radial distributicon curves for the Orbitals show that penetrates Fowarde mere orucleus teen peobital. So screening effect of S according same shen to clatter's rule, the s grouped lagether.. sap asbitals of Periodic Properties 1) Atomic Radius Horense gradius centre of OR the may be defined as the distance from the nuclear to the outer most shell con Atomic radius onay !! containing e be defined as the distance from the contre of nucleus to the point upto which the electron cloud is maximum. density of ties in the determination of atornic radius: Difficulties The exact size of atom can't be the actronic si20 depende determined because repon hybridisation, nuclear Chay can change mo.of orbits, Oxidation state and molecular structure." It & not possible to isolate single atom for the purpose of determination of radius. The prrobability distribution of es is afected by the presence of other atrons. Atom is precent in different bonded state and hybridisa Amition (Covalent Radices of It is one half of the covalently two Covalent! Thus covaleni distance between the nugleik bonded atoons of samo elements of a x inter quclean distance bet ture bunded atims -x bond length -For example- "The bonflength of th molecule = 0.74 A covalent of H aturn Covalent rody Variation ng the period: (i) Along th In general, the atomic radius decreases with incuese ind. atordic number as we move left to a right along a period. 1) As we move from left to Vincreases regularly by right in a 1 unit while period, nuclear charge no. of the shell remains same. Due to this the ees of all the shells pull Closen to the gucleus. As a Hence atomic a little a result the size of atom decreases. decreases (4) Along the encreases group Faz Atom that the nor no of due along the group this is due to the shell enco gases by succeding, elements.As. And by! by one unit in every a result atathic size increases atomic radie increases. Tonic Radius ~ It is glofined on its cloud. as the effective distance from the centre of the upto which of extendog ik influence is The 5120 of cation always smallien than the corresponding Hince the radius of cation in senatten than the radices of ite neutral atorn in the radius of anion is greater greater than that of its neutral atom, Fon 1x: Na, Na wadus: 1.974 0934 1.250.60 Igo electronic Species A no. of species such as neutral atom,cation en onion which have same no of one called the lectiorit Apoin For ex: NỞ No. Na N 0 M Size of Isoelectronic cong Those and such crations or anions which canny. number of 's. the same such uns ane affected toy effective mucican change. Greaten the sμείται jon, greatre will the force of is the same of of s attraction for raut fie of ion decreases In other words, as the magnitude of negative charge increases, the size of anion increasen Similarly as Bare of magnitude of tre Ocation doordases. change increases the the Thus Tonisation Enthalpy (Ionisation energy The minimum amount of energy required to remove loosely borovand most loosely 20% form ash isolated, gases tim eners covert it into gaseous cation is called its Ionisation perif the moke energy. It is theasured in 1kJ/mol on ev per atom unit For example Mat I.E Me Sureessi Successive żonisation energy. The ionisation energy Bred ee from an isola lonisation energy. requited to remove isolated gaseous 1st, 2nd and atom are called succen As the १०. ofs decreases. the effective nuclear choage effecti increases As a result more amount of the be from the to remove the ee energy is required Hence successive form the cation. Hence tricreases sonisation Chery gradually (1.) (IE) (1.E)。 1 Fore Ex Allg 117 te Alg ( AIE AR (1.E) = 577-6 RJ/m I.EX=1816.7KJ/mc) (J.E),=2714.8KJ/NOL Factors affection affecting ionisation energy Ionisation ener depends upon the ng factore following factore 11 ) see of lang meny size agnitude of nuclear charge freitalks (3) Screening effect (4) Penetration effect (5) Stable electronic Configuration Parasani ming 3 1, size of atom sports but Ionisation energy decreases of the atomic the size threes as the distance off the outer eos from the nucleus. Increases the attractive force decreases. A a orce on the order electron resalt, outer electrons are first (ges and hence lessen amount of energy required remove thed, thus 1.5 decrease with increase in atomic size. For eg Na Lu 50 45/01 99543/me