Periodic Table PDF

Z:\NODE02\B0AI-B0\TARGET\CHEM\ENG\MODULE-2\1-PERIODIC TABLE\01THEORY.P65 E Extended or Long Form of the Periodic Table s-Block Elements...

Z:\NODE02\B0AI-B0\TARGET\CHEM\ENG\MODULE-2\1-PERIODIC TABLE\01THEORY.P65 E Extended or Long Form of the Periodic Table s-Block Elements ALLEN p-Block Elements IA 0 Group Metals (1) (18) Period 1 2 Non metals H IIA IIIA IVA VA VIA VIIA He 1 1.0079 4.0026 Hydrogen (2) (13) (14) (15) (16) (17) Helium Metalloids 3 4 5 6 7 8 9 10 2 Li Be B C N O F Ne 3 6.940 Lithium 11 Na 9.0122 Beryllium 12 Mg A IIIB IVB VB VIB d-Block Elements VIIB VIII IB IIB 10.811 Boron 13 Al 12.011 Carbon 14 Si 14.007 Nitrogen 15 P 15.999 Oxygen 16 S 18.998 Fluorine 17 Cl 20.180 Neon 18 Ar 22.990 24.305 26.982 28.086 30.974 32.066 35.453 39.948 Sodium Magnesium (3) (4) (5) (6) (7) (8) (9) (10) (11) (12) Aluminium Silicon Phosphorus Sulphur Chlorine Argon 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 4 K Ca Sc Ti V Cr Mn Fe Co Ni Cu Zn Ga Ge As Se Br Kr 39.098 40.078 44.956 47.867 50.941 51.996 54.938 55.847 58.933 58.693 63.546 65.39 62.723 72.61 74.922 78.96 79.904 83.80 Potassium Calcium Scandium Titanium Vanadium Chrominum Manganese Iron Cobalt Nickel Copper Zinc Gallium Germanium Arsenic Selenium Bromine Krypton 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 5 Rb Sr Y Zr Nb Mo Tc Ru Rh Pd Ag Cd In Sn Sb Te I Xe 85.468 87.62 88.906 91.224 92.906 95.94 98 101.07 102.91 106.42 107.87 112.41 114.82 118.71 121.76 127.60 126.90 131.29 Rubidium Strontium Yttrium Zirconium Niobium Molybdenum Technetium Ruthenium Rhodium Palladium Silver Cadmium Indium Tin Antimony Tellurium Iodine Xenon Se LL 55 56 57 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 6 Cs Ba La* Hf Ta W Re Os Ir Pt Au Hg Tl Pb Bi Po At Rn 132.91 137.33 138.91 178.49 180.95 183.84 186.21 190.23 192.22 195.08 196.97 200.59 204.38 207.2 208.98 210 210 222 Cesium Barium Lanthanum Hafnium Tantalum Tungsten Rhenium Osmium Iridium Platinum Gold Mercury Thallium Lead Bismuth Polonium Astatine Radon ss 87 88 89 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 7 Fr Ra Ac** Unq Unp E io Unh Uns Uno Une Uun Uuu Uub Uut Uuq Uup Uuh Uus Uuo 223 226 227 261 262 266 264 269 268 269 272 277 Francium Radium Actinium Unnilquadium Unnilpentium Unnilhexium Unnilseptium Unniloctium Unnilennium Ununnilium Unununium Ununbium n f-Block Elements 58 59 60 61 62 63 64 65 66 67 68 69 70 71 6 *Lanthanide Series Ce Pr Nd Pm Sm Eu Gd Tb Dy Ho Er Tm Yb Lu 20 140.12 140.91 144.24 145 150.36 151.96 157.25 158.93 162.50 164.93 167.26 168.93 173.07 174.97 7 **Actinide Series Cerium 90 Th 232.04 Praseodymium Neodymium 91 Pa 231.04 92 U 238.03 Promethium 237 93 Np 244 Samarium 94 Pu 19 243 95 Am N Europium Gadolinium 96 Cm 247 Terbium 97 Bk 247 Dysprosium 98 Cf 251 Holmium 99 Es 252 Erbium 100 Fm 257 Thulium 258 101 Md 259 Ytterbium 102 No 262 Lutetium 103 Lr Thorium Protactinium Uranium Neptunium Plutonium Americium Curium Berkelium Californium Einsteinium Fermium Mendelevium Nobelium Lawrencium -2 IUPAC designations of groups of elements are given in brackets 1 Pre-Medical : Chemistry 0 Pre-Medical : Chemistry ALLEN PERIODIC TABLE 1.0 INTRODUCTION : The arrangement of all the known elements according to their properties in such a way that the elements with similar properties are grouped together in a tabular form is called periodic table. DEVELOPMENT OF PERIODIC TABLE (A) LAVOISIER CLASSIFICATION : (i) Lavoisier classified the elements simply in metals and non metals. Metals are the one which have the tendency of losing the electrons. Na ® Na+ + e– and K ® K+ + e– Non-metals are the one which have the tendency of gaining the electrons. F + e– ® F – and Cl + e– ® Cl– N (ii) Drawback or Limitation : (a) As the number of elements increases, this classification became insufficient for the study of elements. 0 (b) There are few elements which have the properties of both metals as well as non-metals and they are -2 called metalloids. Lavoisier could not decide where to place the metalloids. E 19 (B) PROUT'S HYPOTHESIS : He simply assumed that all the elements are made up of hydrogen, so we can say that Atomic weight of element = n × (Atomic weight of one hydrogen atom) 20 LL Atomic weight of H = 1 where n = number of hydrogen atom = 1, 2, 3,.... n Drawback or Limitation : io (i) Every element can not be formed by Hydrogen. ss (ii) Atomic weight of all elements were not found as the whole numbers. Ex. Chlorine (atomic weight 35.5) and Strontium (atomic weight 87.6) Se (C) DOBEREINER TRIAD RULE : A (i) He made groups of three elements having similar chemical properties called TRIAD. (ii) In Dobereiner triad, atomic weight of middle element is nearly equal to the average atomic weight of first and third element. Z:\NODE02\B0AI-B0\TARGET\CHEM\ENG\MODULE-2\1-PERIODIC TABLE\01THEORY.P65 Ex. Cl Br I Ca Sr Ba Li Na K 35.5 80.0 127 40 87.6 137 7 23 39 35.5 + 127 40 + 137 7 + 39 x= = 81.2 x= = 88.5 x = = 23 2 2 2 Where x=average atomic weight (iii) Other examples – (K, Rb, Cs), (P, As, Sb), (S, Se, Te) Drawback or Limitation : All the known elements could not be arranged as triads. It is not applicable for d and f-block elements. 2 E  Pre-Medical : Chemistry ALLEN (D) NEWLAND OCTAVE RULE (i) He arranged the elements in the increasing order of their atomic mass and observed that the properties of every 8th element was similar to the 1st element. (like in the case of musical vowels notation) (ii) At that time inert gases were not known. Sa Re Ga Ma Pa Dha Ni Sa 1 2 3 4 5 6 7 8 H Li Be B C N O F Na Mg Al Si P S Cl K Ca (iii) The properties of Li are similar to 8th element i.e. Na and Be are similar to Mg and so on. Drawback or Limitation : (a) This rule is valid only upto Ca because after Ca due to presence of d-block element there is a difference N of 18 elements instead of 8 elements. (b) After the discovery of Inert gas and including them in the periodic table, it has become the 8th element from Alkali metal so this law had to be dropped out. 0 (E) LOTHAR MEYER'S CURVE : -2 (i) He plotted a curve between atomic weight and atomic volume of different elements. (ii) E The following observation can be made from the curve – 19 (a) Most electropositive elements i.e. alkali metals (Li, Na, K, Rb, Cs) occupy the peak positions on the curve. (b) Less electropositive i.e. alkaline earth metal (Be, Mg, Ca, Sr, Ba) occupy the descending position 20 on the curve. LL (c) Metalloids (Si, Ge, As, Sb, Te, Po, At) and transition metals occupy bottom part of the curve. (d) Most electronegative i.e. halogens (F, Cl, Br, I) occupy the ascending position on the curve. n Note : Elements having similar properties occupy similar position on the curve. io Conclusion : On the basis of this curve Lother Meyer proposed that the physical properties of the elements are periodic function of their atomic weight and this has become the base of Mendeleev's periodic table. ss Periodic function : When the elements are arranged in the increasing order of their atomic weight, elements having similar properties gets repeated after a regular interval. Se A Cs Atomic Volume I Z:\NODE02\B0AI-B0\TARGET\CHEM\ENG\MODULE-2\1-PERIODIC TABLE\01THEORY.P65 Rb Ba Br K Sr Na Cl F Ca Li Mg Be Metalloid and transition metals Atomic Weight E 3 Pre-Medical : Chemistry ALLEN (F) MENDELEEV'S PERIODIC TABLE : (i) Mendeleev's periodic law : The physical and chemical properties of elements are the periodic function of their atomic weight. (ii) Characteristics of Mendeleev's periodic table : (a) It is based on atomic weight (b) 63 elements were known, noble gases were not discovered. (c) He was the first scientist to classify the elements in a systematic manner i.e. in horizontal rows and in vertical columns. (d) Horizontal rows are called periods and there were 7 periods in Mendeleev's Periodic table. (e) Vertical columns are called groups and there were 8 group in Mendeleev's Periodic table. (f) Each group upto VII is divided into A & B subgroups.'A' sub group element are called normal or representative elements and 'B' sub group elements are called transition elements. (g) The VIII group consisted of 9 elements in three rows (Transitional metals group). N (h) The elements belonging to same group exhibit similar properties. (iii) Merits or advantages of Mendeleev's periodic table : (a) Study of elements : First time all known elements were classified in groups according to their 0 similar properties. So study of the properties of elements become easier. -2 (b) Prediction of new elements : It gave encouragement to the discovery of new elements as E some gaps were left in it. 19 Sc (Scandium) Ga (Gallium) Ge (Germanium) Tc (Technetium) These were the elements for whom position and properties were well defined by Mendeleev even 20 before their discoveries and he left the blank spaces for them in his table. LL Ex. Blank space at atomic weight 72 in silicon group was called Eka silicon (means properties like silicon) and element discovered later was named Germanium. n Similarly other elements discovered after mendeleev's periodic table were. io Eka Aluminium - Galium(Ga) Eka Boron - Scandium (Sc) ss Eka Silicon - Germanium (Ge) Eka Mangenese - Technetium (Tc) (c) Correction of doubtful atomic weights : Correction were done in atomic weight of some Se elements. A Atomic weight = Valency × Equivalent weight. Initially, it was found that equivalent weight of Be is 4.5 and it is trivalent (V = 3), so the weight of Be was 13.5 and there is no space in Mendeleev's table for this element. So, after correction, it Z:\NODE02\B0AI-B0\TARGET\CHEM\ENG\MODULE-2\1-PERIODIC TABLE\01THEORY.P65 was found that Be is actually bivalent (V = 2). So, the weight of Be became 2 × 4.5 = 9 and there was a space between Li and B for this element in Mendeleev's table. Corrections were done in atomic weight of elements are – U, Be, In, Au, Pt. (iv) Demerits of Mendeleev's periodic table : (a) Position of hydrogen : Hydrogen resembles both, the alkali metals (IA) and the halogens (VIIA) in properties so Mendeleev could not decide where to place it. (b) Position of isotopes : As atomic wt. of isotopes differs, they should have placed in different position in Mendeleev's periodic table. But there were no such places for isotopes in Mendeleev's table. 4 E  Pre-Medical : Chemistry ALLEN (c) Anomalous pairs of elements : There were some pair of elements which did not follow the increasing order of atomic weights. Ex. Ar and Co were placed before K and Ni respectively in the periodic table, but having higher atomic weights. Ar K Te I 39.9 39.1 127.5 127 Co Ni Th Pa 58.9 58.6 232 231 (d) Like elements were placed in different groups : There were some elements like Platinum (Pt) and Gold (Au) which have similar properties but were placed in different groups in Mendeleev's table. Pt Au VIII IB (e) Unlike elements were placed in same group : N St I group 0 IA IB Li -2 Na (Bridge Element) E 19 More reactive K Cu Less reactive Alkali metal Rb Ag Coinage metal Normal elements Cs Au Transition element 20 LL n io ss Cu, Ag and Au placed in Ist group along with Na, K etc. While they differ in their properties (Only similar in having ns1 electronic configuration) Se (f) It was not clear that 'lanthanides and Actinides' are related with IIIA group or IIIB group. (g) Cause of periodicity : Why physical & chemical properties repeated in a group. A Z:\NODE02\B0AI-B0\TARGET\CHEM\ENG\MODULE-2\1-PERIODIC TABLE\01THEORY.P65 1. Mendeleev's periodic law is based on - (1) Atomic number (2) Atomic weight (3) Number of neutrons (4) None of the above 2. The first attempt to classify elements systematically was made by - (1) Mendeleev (2) Newland (3) Lother Meyer (4) Dobereiner 3. Atomic weight of an element X is 39, and that of element Z is 132. atomic weight of their intermediate element Y, as per dobereiner triad, will be (1) 88.5 (2) 93.0 (3) 171 (4) 85.5 4. Which of the following is not a dobereiner triad (1) Li, Na, K (2) Mg, Ca, Sr (3) Cl, Br, I (4) S, Se, Te E 5 Pre-Medical : Chemistry ALLEN 5. The law of triads is applicable to (1) C, N, O (2) H, O, N (3) Na, K, Rb (4) Cl, Br, I 6. The law of triads is not applicable on (1) Cl, Br, I (2) Na, K, Rb (3) S, Se, Te (4) Ca, Sr, Ba 7. Which of the following set of elements obeys Newland's octave rule – (1) Na, K, Rb (2) F, Cl, Br (3) Be, Mg, Ca (4) B, Al, Ga 8. For which of the pair Newland octave rule is not applicable – (1) Li, Na (2) C, Si (3) Mg, Ca (4) Cl, Br 9. Which of the following element was present in Mendeleev's periodic table? N (1) Sc (2) Tc (3) Ge (4) None of these 10. Is Fe, Co, Ni are dobereiner triad ? 0 -2 1.1 MODERN PERIODIC TABLE (MODIFIED MENDELEEV PERIODIC TABLE) : E 19 (i) It was proposed by Moseley. (ii) Modern periodic table is based on atomic number. (iii) Moseley did an experiment in which he bombarded high speed electron on different metal surfaces and obtained X-rays. 20 LL He found out that n µ Z where n = frequency of X-rays, Z = atomic number.. n From this experiment, Moseley concluded that the physical and chemical properties of the elements are io periodic function of their atomic number. It means that when the elements are arranged in the increasing order of their atomic number elements having similar properties gets repeated after a regular interval. ss This is also known as 'Modern Periodic Law'. (iv) Modern periodic law : The physical & chemical properties of elements are the periodic function of their atomic number. Se (v) Characteristics of modern periodic table : A (a) 9 vertical columns called groups. (b) I to VIII group + 0 group of inert gases. Z:\NODE02\B0AI-B0\TARGET\CHEM\ENG\MODULE-2\1-PERIODIC TABLE\01THEORY.P65 (c) Inert gases were introduced in periodic table by Ramsay. (d) 7 horizontal rows called periods. LONG FORM / PRESENT FORM OF MODERN PERIODIC TABLE : (It is also called as 'Bohr, Bury, Rang & Werner Periodic Table) (i) It is based on the Bohr-Bury electronic configuration concept and atomic number. (ii) This model is proposed by Rang & Werner (iii) 7 periods and 18 groups (iv) According to I. U. P. A. C. 18 vertical columns are named as 1st to 18th group. 6 E  Pre-Medical : Chemistry ALLEN (v) The co-relation between the groups in long form of periodic table and in modern form of periodic table are given below – IA IIA IIIB IVB VB VIB VIIB VIII IB IIB IIIA IVA VA VIA VIIA 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 (vi) Elements belonging to same group have same number of electrons in the outermost shell so their properties are similar. Description of periods Period n Period Sub shell No. of elements Element Name of Period 1. 1 1s 2 H – 2He 1 Shortest 2. 2 2s, 2p 8 Li – 10Ne 3 Short 3. 3 3s, 3p 8 11 Na – 18Ar Short 4. 4 4s, 3d, 4p 18 19 K – 36Kr Long 5. 5 5s, 4d, 5p 18 37 Rb – 54Xe Long 6. 6 6s, 4f, 5d, 6p 32 Cs – 86Rn Longest N 55 7. 7 7s, 5f, 6d, 7p 32 87 Fr – Uuo 118 Complete CONCLUSION 0 1. Period number = outermost shell -2 2. Number of element in a period = Number of electrons in a period subshell E DESCRIPTION OF GROUPS : 19 1st/IA/Alkali metals 2nd/IIA/Alkaline earth metals H = 1s1 Be = 1s2, 2s2 Li = 1s2 , 2s1 Mg = 1s2, 2s2 2p6, 3s2 20 LL Na = 1s2 , 2s2 2p6 , 3s 1 Ca = 1s2, 2s2 2p6, 3s2 3p6, 4s2 K = 1s2 , 2s2 2p6 , 3s2 3p6 , 4s1 General electronic configuration = ns2 n General electronic configuration = ns1 (n = Number of shell) io Number of valence shell e– = 1 Number of valence shell e– = 2 ss 13th/IIIA/Boron Family 14th/IVA/Carbon Family B = 1s2, 2s2 2p1 C = 1s2, 2s2 2p2 Se Al = 1s2, 2s 2 2p6, 3s2 3p1 Si = 1s2, 2s2 2p6, 3s2 3p2 A Ga = 1s 2, 2s2 2p6, 3s 2 3p6 3d10, 4s2 4p1 Ge = 1s2, 2s2 2p6, 3s2 3p6 3d10, 4s2 4p2 General electronic configuration = ns2 np1 General electronic configuration = ns2 np2 Number of valence shell e– = 3 Number of valence e– = 4 Z:\NODE02\B0AI-B0\TARGET\CHEM\ENG\MODULE-2\1-PERIODIC TABLE\01THEORY.P65 15th/VA/Nitrogen family/Pnicogen 16th/VIA/Oxygen family/Chalcogen (Used in fertilizer as urea) (Ore forming) N = 1s2, 2s2 2p3 O = 1s2, 2s2 2p4 P = 1s 2, 2s 2 2p6, 3s2 3p3 S = 1s2, 2s2 2p6, 3s2 3p4 As = 1s2, 2s2 2p6, 3s2 3p6 3d10, 4s 2 4p3 Se = 1s2, 2s2 2p6, 3s2 3p6 3d10, 4s2 4p4 General electronic configuration = ns2 np3 General electronic configuration = ns2 np4 Number of valence shell e– = 5 Number of valence shell e– = 6 E 7 Pre-Medical : Chemistry ALLEN 17th/VIIA/Fluorine family/Halogens 18th/Zero group/Inert gases / Noble gases (Salt forming) (Less reactive) F = 1s2, 2s2 2p5 Ne = 1s2, 2s2 2p6 Cl = 1s2, 2s2 2p6, 3s2 3p5 Kr = 1s2, 2s2 2p6, 3s2 3p6 3d10, 4s2 4p6 Br = 1s2, 2s2 2p6, 3s2 3p6 3d10, 4s2 4p 5 General electronic configuration = ns 2 np6 (except He) General electronic configuration = ns 2 np5 Number of valence shell e– = 8 Number of valence shell e– = 7 (vii) NOMENCLATURE OF ELEMENTS : (a) IUPAC gave names to elements above atomic number 100 as follows – 0 1 2 3 4 5 6 7 8 9 nil un bi tri quad pent hex sept oct enn (b) In all the elements suffix is – ium. N Ex. Atomic No. IUPAC Name Symbol Elemental Name Symbol 101 Un nil unium Unu Mendelevium Md 0 102 Un nil bium Unb Nobelium No -2 E 103 Un nil trium Unt Lawrencium Lr 19 104 Un nil quadium Unq Rutherfordium Rf 105 Un nil pentium Unp Dubnium Db 106 Un nil hexium Unh Seaborgium 20 Sg LL 107 Un nil septium Uns Bohrium Bh 108 Un nil octium Uno Hassium Hs n 109 Un nil ennium Une Meitnerium Mt io 110 Un un nilium Uun Darmstadtium Ds ss (viii) Identification of group, period and block : Se (A) When atomic number is given : A Step I : 71 ³ Z ³ 58 Þ Lanthanoids (6th Period) f-block 103 ³ Z ³ 90 Þ Actinoids (7 Period) th Group number = IIIB (largest group of periodic table) Z:\NODE02\B0AI-B0\TARGET\CHEM\ENG\MODULE-2\1-PERIODIC TABLE\01THEORY.P65 Step II : Z = 104 to 118 (Period number = 7) Group number = last two digits in atomic number of element Example : Z = 104 Group no. = 4 Step III : Group number = 18 + given atomic number – atomic number of next noble gas If the value of this formula is negative then use 32 instead of 18 in formula. 8 E  Pre-Medical : Chemistry ALLEN (B) When electronic configuration is given Period number (n) = number of outermost shell/Highest shell number. Block identification : If np electron present then p - block (ns2 np1–6) group number = 12 + np electrons If np electron absent then s/f/d block If (n–2)f0 (n–1)d0 ns1–2 = s block group number = ns electrons If (n–2)f1–14 (n–1)d0–1 ns2 = f block group number = IIIB If any other configuration or (n–1)d1–10 ns0–2 (d-block) group number = (n–1)d electron + ns electron Bohr's Classification Inert gases Normal or Transition element Inner transition element representative elements N outermost shell outermost shell incomplete n & n–1 shells n, (n–1), (n–2) complete incomplete shells incomplete either in atomic or 0 ionic form -2 6 element s & p block element all d block element f-block elements E except inert gas except = 28 elements 19 38 element IIB (Zn, Cd, Hg & Uub) 36 element SOME IMPORTANT POINTS : 20 LL (a) 2nd period elements (Li, Be, B) Shows diagonal relationship with 3rd period elements (Mg, Al, Si). Because of same ionic potential value they shows similarity in properties. n Charge on cation (Ionic potential (f) = ) io Radius of cation Li Be B ss Na Mg Al Si Se (b) 3rd period elements (Na, Mg, Al, Si, P, S, Cl) except inert gases are called typical elements because A they represent the properties of other element of their respective group. (c) TRANSURANIC ELEMENTS : Elements having atomic number more than 92 are known as transuranic element. All transuranic elements are radioactive & artificial. Z:\NODE02\B0AI-B0\TARGET\CHEM\ENG\MODULE-2\1-PERIODIC TABLE\01THEORY.P65 f-block d-block Th Pa U Np Lr Unq Uub 90 91 92 93 103 104 112 First man made element is Tc First man made lanthanoid is Pm All actinoids are radioactive but all lanthanoids are not artificial / man made (except Pm) (d) The group containing most electro positive elements – GROUP IA. (e) The group containing most electro negative elements – GROUP VIIA (f) The group containing maximum number of gaseous elements–GROUP ZERO(18th) E 9 Pre-Medical : Chemistry ALLEN (g) The group in which elements have generally ZERO valency – GROUP ZERO(18th) (h) In the periodic table Number of Gaseous elements – 11 (H, N, O, F, Cl + Noble gases) Number of Liquid elements – 6 (Cs, Fr, Ga, Hg, Br, Uub) Number of Liquid elements at room temp. –2 Bromine is the only non-metal which exists in liquid form. Number of Solid elements – 95 (if discovered elements are 112) (i) 0/18 group have all the elements in gaseous form. (j) 2nd period contains maximum number of gaseous elements. They are 4 (N, O, F, Ne) (k) IIIB/3rd group is called longest group having 32 elements including 14 Lanthanides and 14 Actinides Sc Y La................Lanthanides (14) Ac................Actinides (14) N 1. Which of the following is best general electronic configuration of normal element (1) ns1–2 np0–6 (2) ns1–2 np1–5 (3) ns1–2 np0–5 (4) ns1–2 np1–6 2. Which of the following set of atomic numbers represents representative element 0 (1) 5, 13, 30, 53 (2) 11, 33, 58, 84 (3) 5, 17, 31, 54 (4) 9, 31, 53, 83 -2 3. Which of the following electronic configuration does not belongs to same block as others :- E (1) [Xe] 4f14 5d10 6s2 (2) [Kr] 4d10 5s2 (3) [Kr] 5s2 (4) [Ar] 3d6 4s2 19 4. The electronic configuration of an element is 1s22s22p63s23p63d104s1. What is the atomic number of next element of the same group which is recently discovered :- (1) 20 (2) 119 (3) 111 20 (4) None LL 5. Which of the following electronic configurations in the outermost shell is characteristic of alkali metals (1) (n–1) s2p6 ns2p1 (2) (n–1) s2p6d10 ns1 (3) (n–1) s2p6 ns1 (4) ns2np6 (n–1)d10 n 6. Which of the following elements belong to alkali metals ? io (1) 1s2, 2s2 2p2 (2) 1s2, 2s2 2p6, 3s2 3p6 3d10, 4s2 4p6, 5s1 (3) 1s2, 2s2 2p5 (4) None of these ss 7. Elements whose atoms have three outermost shells incomplete are called – (1) s-block (2) p-block (3) d-block (4) f-block Se 8. Which of the following statement is wrong :- A (1) All the actinides are synthetic (man made) elements (2) In the Lanthanides last electron enters in 4f orbitals (3) Np93 onwards are transuranic elements Z:\NODE02\B0AI-B0\TARGET\CHEM\ENG\MODULE-2\1-PERIODIC TABLE\01THEORY.P65 (4) Lanthanum is d–block element 9. Which of the following statement is wrong :- (1) Total no. of liquid elements in the periodic table.....Six (2) First metal element in the periodic table is....Li (3) All type of elements are present in 6th period (4) Iodine is a gaseous element. 10. An element which is recently discovered is placed in 7th period and 10th group. IUPAC name of the element will be :- (1) Unnilseptium (2) Ununnilium (3) Ununbium (4) None 10 E  Pre-Medical : Chemistry ALLEN 1.2 PERIODICITY (A) In a period, the ultimate orbit remain same, but the number of e– gradually increases. In a group, the number of e– in the ultimate orbit remains same, but the values of n increases. (B) Causes of periodicity : (a) The cause of periodicity in properties is due to the same outermost shell electronic configuration coming at regular intervals. (b) In the periodic table, elements with similar properties occur at intervals of 2, 8, 8, 18, 18 and 32. These numbers are called as magic numbers. SCREENING EFFECT (s) AND EFFECTIVE NUCLEAR CHARGE (Zeff) : (i) Valence shell e– suffer force of attraction due to nucleus and force of repulsion due to inner shell electrons. (ii) The decrease in force of attraction on valence e– due to inner shell e– is called screening effect or shielding effect.(i.e. total repulsive force is called shielding effect.) (iii) Due to screening effect valence shell e– experiences less force of attraction exerted by nucleus. i.e. total attraction force experieced by valence electrons represented by a number is Zeff. N (iv) There is a reduction in nuclear charge due to screening effect. Reduced nuclear charge is called effective nuclear charge. 0 (v) If nuclear charge = Z, effective nuclear charge = Zeff , s (Sigma)= Screening constant or shielding constant. -2 So, Zeff = ( Z - s ) l E Slater's rule to know screening constant (s) 19 (a) For single electron species s = 0 (b) Screening effect (S.E.) for two e– species 0.30 Ex. In He (1s2) 20 LL Screening effect of one 1s e–. where s = 0.30 \ Zeff = Z – s = 2 – 0.30 = 1.7 n (c) Screening effect of each ns and np (Outermost orbit) electrons is 0.35 io (d) Screening effect of each (n – 1) penultimate orbit s, p, d electrons is 0.85 ss (e) Screening effect of each (n – 2) and below all the e– present in s, p, d, f is 1.0 From top to bottom in a group Zeff remain constant Se Group Element Li Na K Rb Cs Fr A Zeff 1.30 2.20 2.20 2.20 2.20 2.20 Period Element Be B C N O F Zeff 1.95 2.6 3.25 3.90 4.55 5.20 Z:\NODE02\B0AI-B0\TARGET\CHEM\ENG\MODULE-2\1-PERIODIC TABLE\01THEORY.P65 For same shell shielding effect has the order as s > p > d > f (due to penetration effect) Zeff for different ions of an element positive charge ( i ) Zeff for different ions of an element Zeff µ negative charge (ii) Z eff for isoelectronic species. (i) Zeff for different ions of an element Ex. N+ > N > N– = Zeff (ii) Zeff of isoelectronic species Ex. H– < Li+ < Be+2 < B+3 (2e– species) N–3 < O–2 < F– < Na+ < Mg+2 (10e– species) E 11 Pre-Medical : Chemistry ALLEN 1.3 ATOMIC RADIUS The average distance of valence shell e– from nucleus is called atomic radius. It is very difficult to measure the atomic radius because – (i) The isolation of single atom is very difficult. (ii) There is no well defined boundary for the atom. (The probability of finding the e– is 0 only at infinity). So, the more accurate definition of atomic radius is – l Half the inter-nuclear distance(d) between two atoms in a homoatomic molecule is known as atomic radius. l This inter-nuclear distance is also known as bond length. Inter-nuclear distance depends upon the type of bond by which two atoms combine. Based on the chemical bonds, atomic radius is divided into four categories – (A) Covalent radius (B) Ionic radius (C) Metallic radius (D) van der Waal's radius (A) Covalent Radius (SBCR –Single Bonded Covalent Radius) N (a) Covalent bonds are formed by overlapping of atomic orbitals. (b) Internuclear distance is minimum in this case. 0 (c) Covalent radius is the half of the internuclear distance between two singly bonded homo atoms. -2 E Ex. If internuclear distance of A–A(A2) molecule is (dA – A) and covalent radius is rA then 19 dA–A = rA + rA or 2rA rA = dA-A 2 20 LL 1.98 Ex. In Cl2 molecule, internuclear distance is 1.98A0 so rcl = = 0.99 Å n 2 io (B) Ionic Radius (i) Cationic Radius ss (a) When an neutral atom loses e– it converts into cation (+ve charged ion) (b) Cationic radius is always smaller than atomic radius because after loosing e– number of e– reduces, but Se number of protons remains same, due to this Zeff increases, hence electrons are pulled towards nucleus and A atomic radius decreases, moreover after loosing all the electrons from the outer most shell, penultimate shell becomes ultimate shell which is nearer to nucleus so size decreases. 1 Z:\NODE02\B0AI-B0\TARGET\CHEM\ENG\MODULE-2\1-PERIODIC TABLE\01THEORY.P65 (c) Size of cation µ Magnitude of the charge or Z eff Ex. (i) Fe > Fe+2 > Fe+3 (ii) Pb+2 > Pb+4 (iii) Mn > Mn+2 > Mn+3 > Mn+4 > Mn+5 > Mn+6 > Mn+7 12 E  Pre-Medical : Chemistry ALLEN (ii) Anionic Radius (a) When a neutral atom gains e– it converts into anion [Negative charge ion] (b) Anionic radius is always greater than atomic radius because in an anion e– are more than protons and inter electronic repulsion increases, which also increases screening effect. So effective nuclear charge reduces, so distance between e– and nucleus increases and size of anion also increases. Ex. Flourine (Z=9) F F– Proton 9 9 e – 9 10 Z 9 9 so = =1 = 0.9 As Zeff of F– is less than F so size of F– > F e 9 10 (c) Size of isoelectronic species : Those species having same number of e– but different nuclear charge forms isoelectronic series. For isoelectronic species the atomic radius increases with decrease in effective nuclear charge Species K+ Ca+2 S–2 Cl– N Z 19 20 16 17 e 18 18 18 18 0 Z 19 20 16 17 e 18 18 18 18 -2 Order of radius : (S–2 > Cl– > K+ > Ca+2), E (N3–> O2–> F–> Na+ > Mg+2 > Al+3) 19 18 e– 10 e– (C) Metallic/Crystal Radius 20 (a) Half of the inter nuclear distance between two adjacent metallic atoms in crystalline lattice structure. LL (b) there is no overlapping of atomi