UNIT Periodic Classification 12 of Elements

Learning Objectives

After completing this lesson, students will be able to „„ know the concept of classification of elements in early days. „„ understand the postulates, advantages and limitations of modern periodic table. „„ understand the classification of elements based on the electronic configuration. „„ learn about the position of hydrogen in the periodic table. „„ study about the position of rare gases (Noble gases) in the periodic table. „„ distinguish between metals and non-metals. „„ know about metalloids and alloys.

Introduction 12.1. Early Concepts of Classification of We live in the world of substances with Elements great diversity. Substances are formed by the 12.1.1. Dobereiner’s Triads combination of various elements. All the elements are unique in their nature and property. In 1817, Johann Wolfgang Dobereiner, To categorize these elements according to their a German chemist, suggested a method of properties, scientists started to look for a way. grouping elements based on their relative In 1800, there were only 31 known elements. atomic masses. He arranged the elements into By 1865, their number became 63. Now 118 groups containing three elements each. He elements have been discovered. As different called these groups as ‘triads’ (tri – three). elements were being discovered, scientists Dobereiner showed that when the three gathered more and more information about elements in a triad are arranged in the ascending the properties of these elements. They found it order of their atomic masses, the atomic mass difficult to organize all that was known about of the middle element is nearly the same as the elements. They started looking for some average of atomic masses of other two elements. pattern in their properties, on the basis of This statement is called the Dobereiner’s law which they could study such a large number of of triads. Table 12.1 shows the law of triads elements with ease. Let us discuss the concepts proposed by Dobereiner. of classification of elements proposed by various Example: In the triad group (1), arithmetic scientists from early to modern period. mean of atomic masses of 1st and 3rd elements,

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IX_SCI_EM_Unit-12_CHE.indd 138 09-03-2019 12:21:09 Table 12.1 Dobereiner's law of triads Triad Group (1) Triad Group (2) Triad Group (3) Element Atomic Mass Element Atomic Mass Element Atomic Mass Li 6.9 Cl 35.5 Ca 40.1 Na 23 Br 79.9 Sr 87.6 K 39.1 I 126.9 Ba 137.3

(6.9 + 39.1)/2 = 23. So the atomic mass of Na ™™ Some elements, totally dissimilar in their (middle element) is 23. properties, were fitted into the same group. Limitations: (Arrangement of Co, Ni, Pd, Pt and Ir in the row of halogens) „„ Dobereiner could identify only three triads ™™ The law of octaves was not valid for elements from the elements known at that time and that had atomic masses higher than that of all elements could not be classified in the calcium. form of triads. ™ „„ The law was not applicable to elements ™ Newlands’ table was restricted to only 56 having very low and very high atomic elements and did not leave any room for mass. new elements. ™™ Discovery of inert gases (Neon. Argon….) 12.1.2 Newlands’ Law at later stage made the 9th element similar of Octaves to the first one. Eg: Neon between Fluorine In 1866, John Newlands arranged 56 and Sodium. known elements in the increasing order of their 12.1.3 Mendeleev’s Periodic atomic mass. He observed that every eighth Table element had properties similar to those of the first element like the eighth note in an octave of In 1869, Russian chemist, Dmitri music is similar to the first. This arrangement Mendeleev observed that the elements of similar was known as 'law of octaves'. properties repeat at regular intervals when the elements are arranged in the order of their The octave of Indian music system is sa, atomic masses. Based on this, he proposed the re, ga, ma, pa, da, ni, sa. The first and last notes law of periodicity which states that “the physical of this octave are same i.e. sa. Likewise, in the and chemical properties of elements are the Newlands’ table of octaves, the element ‘F’ is periodic functions of their atomic masses”. eighth from the element ‘H’, thus they have He arranged 56 elements known at that time similar properties. according to his law of periodicity. This was best known as the short form of periodic table. Activity 1 (a) Features of Mendeleev’s Periodic Table: Find the pair of elements having similar ™™ It has eight vertical columns called ‘groups’ properties by applying Newlands’ law of and seven horizontal rows called ‘period’. Octaves (Example: Mg & Ca): ™™ Each group has two subgroups ‘A’ and ‘B’. Set I : F, Mg, C, O, B All the elements appearing in a group were Set II: Al, Si, S, Cl, Ca found to have similar properties. ™™ For the first time, elements were Limitations: comprehensively classified in such a way ™™ There are instances of two elements being that elements of similar properties were fitted into the same slot, e.g. cobalt and nickel. placed in the same group.

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IX_SCI_EM_Unit-12_CHE.indd 139 09-03-2019 12:21:09 Table 12.2 Newland’s table of octaves (oct- eight) No. No. No. No. No. No. No. No. H 1 F 8 Cl 15 Co & Ni 22 Br 29 Pd 36 I 42 Pt & Ir 50 Li 2 Na 9 K 16 Cu 23 Rb 30 Ag 37 Cs 44 Os 51 G 3 Mg 10 Ca 17 Zn 24 Sr 31 Cd 38 Ba & V 45 Hg 52 Bo 4 Al 11 Cr 19 Y 25 Ce & La 33 U 40 Ta 46 Ti 53 C 5 Si 12 Ti 18 In 26 Zr 32 Sn 39 W 47 Pb 54 N 6 P 13 Mn 20 As 27 Di & Mo 34 Sb 41 Nb 48 Bi 55 O 7 S 14 Fe 21 Se 28 Ro & Ru 35 To 43 Au 49 Th 56

™™ It was noticed that certain elements could and Eka Silicon to those elements which not be placed in their proper groups in this were to be placed below Aluminium manner. The reason for this was wrongly and Silicon respectively in the periodic determined atomic masses. Consequently table and predicted their properties. The those wrong atomic masses were corrected. discovery of Germanium later on, during Eg: The atomic mass of beryllium was known his life time, proved him correct. to be 14. Mendeleev reassessed it as 9 and assigned beryllium a proper place. (b) Limitations: ™™ Columns were left vacant for elements ™™ Elements with large difference in properties which were not known at that time and their were included in the same group. Eg: Hard properties also were predicted. This gave metals like copper (Cu) and silver (Ag) motivation to experiment in Chemistry. were included along with soft metals like Eg: Mendeleev gave names Eka Aluminium sodium (Na) and potassium (K). Table 12.3 Mendeleev's Periodic Table Group I II III IV V VI VII VIII

Oxide: R2O RO R2 O3 RO2 R2O5 RO3 R2O7 RO4 Hydride: RH RH4 RH4 RH4 RH3 RH2 RH Periods A B A B A B A B A B A B A B Transition series H 1 1.008 Li Be B C N O F 2 6.939 9.012 10.81 12.011 14.007 15.999 18.988 Na Mg Al Si P S Cl 3 22.99 22.99 24.31 28.09 30.974 32.06 35.453 4 First K Ca Sc Ti V Cr Mn Series 39.102 40.08 44.96 47.90 50.94 50.20 54.94 Fe Co Ni Second Cu Zn Ga Ge As Se Br 55.85 58.93 58.71 series 63.54 65.54 69.72 72.59 74.92 78.96 79.909 5 First Rb Sr Y Zr Nb Mo Tc Series 85.47 87.62 88.91 91.22 92.91 95.94 99 Ru Rh Pd Second Ag Cd In Sn Sb Te I 101.07 102.91 106.4 series 107.87 112.40 114.82 118.69 121.60 127.60 126.90 6 First Cs Ba La Hf Ta W Series 132.90 137.34 138.91 178.40 180.95 183.85 Os Ir Pt Second Au Hg Tl Pb Bi 190.2 192.2 195.05 series 196.97 200.59 204.37 207.19 208.98 Rn Fr Ra Ac Th Pa U 7 222 223 226 227 232 231 238

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IX_SCI_EM_Unit-12_CHE.indd 140 09-03-2019 12:21:09 ™™ No proper position could be given to the configuration) in atoms. Hence, the modern element hydrogen. Non-metallic hydrogen periodic law can be stated as follows: “The was placed along with metals like lithium chemical and physical properties of elements (Li), sodium (Na) and potassium (K). are periodic functions of their atomic ™™ The increasing order of atomic mass numbers”. Based on the modern periodic law, was not strictly followed throughout. the modern periodic table is derived. Eg. Co & Ni, Te & I. ™™ No place for isotopes in the periodic table. 12.2.2 Features of Modern Periodic Table Table 12.4 Properties of Germanium „„ All the elements are arranged in the Mendeleev’s Actual increasing order of their atomic number. Property prediction property „„ The horizontal rows are called periods. (1871) (1886) There are seven periods in the periodic Atomic About 72 72.59 table. Mass „ Specific „ The elements are placed in periods based on 5.5 5.47 Gravity the number of shells in their atoms. Colour Dark grey Dark grey „„ Vertical columns in the periodic table starting Formula from top to bottom are called groups. There EsO GeO of Oxide 2 2 are 18 groups in the periodic table. Nature of EsCl GeCl „„ Chloride 4 4 Based on the physical and chemical properties of elements, they are grouped into various families. 12.2 Modern Periodic Table Table 12.5 Groups in modern periodic table

In 1913, the English Physicist Henry Moseley, Group Families through his X-ray diffraction experiments, 1 Alkali metals proved that the properties of elements depend on 2 Alkaline earth metals the atomic number and not on the atomic mass. 3 to 12 Transition metals Consequently, the modern periodic table was 13 Boron Family prepared by arranging elements in the increasing 14 Carbon Family order of their atomic number. 15 Nitrogen Family This modern periodic table is the extension 16 Oxygen Family (or) Chalcogen of the original Mendeleev’s periodic table and Family known as the long form of periodic table. 17 Halogens 18 Noble gases 12.2.1 Modern Periodic Law

Atomic number of an element (Z) 12.2.3 Classification of indicates the number of protons (positive elements into blocks charge) or the number of electrons (negative charge). The physical and chemical properties We know that the electrons in an atom are of elements depend not only on the number accommodated in shells around the nucleus. of protons but also on the number of Each shell consists of one or more subshells in electrons and their arrangements (electronic which the electrons are distributed in certain

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IX_SCI_EM_Unit-12_CHE.indd 141 09-03-2019 12:21:09 (262) (294) (222) VIIIA 131.29 39.948 83.798 20.180 4.0026 174.97 NEO N Xe Ne Ar Lr Kr XENO N He RADO N ARGO N Rn Og Lu HELIUM KRYPTON LUTETIU M 86 18 2 118 10 36 OGANESSO N 18 54 71 103 LAWRENCIUM II A (294) (210) (259) 35.4 5 I 126.90 79.904 173.05 18.998 F Cl At Ts Br IODIN E No Yb BROMIN E ASTATINE FLUORINE CHLORIN E ENNESSINE NOBELIUM YTTERBIU M 17 9 85 117 35 53 17 70 102 M R VI AV (258) (291) (209) 32.0 6 78.971 127.60 168.93 15.999 S O Se Te Po HULIUM Lv ELENIUM OXYGE N ELLURIU Tm Md SULPHU IVERMORIUM POLONIUM 16 8 84 116 52 MENDELEVIUM 16 69 34 101 VA (289) (257) 30.974 121.76 74.922 208.98 14.007 167.26 P N Bi ISMUTH As Sb Er NTIMON YT ERBIU MT Mc Fm ARSENI CS FERMIU M NITROGEN 15 7 MOSCOVIU MT 83 33 51 68 115 PHOSPHORU S 15 100 IVA (287) (252) 72.6 4 207. 2 118.71 12.011 28.085 164.93 TI NA C Si Fl LEA DB Es Sn Pb Ge Ho SILICON CARBO N HOLMIUM FLEROVIU ML GERMANIUM 82 14 114 32 67 14 6 99 50 EINSTEINIUM IIIA a (285) (251) 10.8 1 26.982 114.82 204.38 69.723 162.50 B Tl In Al Cf INDIUM Dy BORON Nh GALLIUM THALLIUM NIHONIUM ALUMINIUM 31 113 66 81 49 13 5 13 98 CALIFORNIU M DYSPROSIU M II B (285) (247) 65.3 8 112.41 158.93 200.59 ZINC ERBIU M Zn Tb Bk Hg Cd Cn ERKELIUM CADMIUM MERCURY COPERNICIU M 12 30 80 65 97 112 48 IB (280) (247) 196.97 107.87 157.25 63.546 URIU MB OPPER GOLD Ag Rg SILVER Cu Au Gd s - synthetic - solid Cm

ROENTGENIU M 11 29 47 GADOLINIU MT 64 79 96 111 Tc Fe Nonmetal Chalcogens element Halogens element Noble ga (281) (243) 106.42 58.693 195.08 151.96 d Pt Ni Ds Pd Eu NICKE LC Am PLATINU M EUROPIUM PALLADIUM AMERICIU MC 63 78 10 28 95 46 DARMSTADTIUM 110 - liqui - gas 2 STANDARD STATE (25 °C; 101 kPa) Ne Hg (244) (276) 102.91 192.2 150.3 6 58.933 Ir VIIIB RIDIUM HODIUM Pu Co Mt Rh COBAL T Sm Semimetal LUTONIUM SAMARIUM 62 9 27 109 MEITNERIU M 94 77 45 MR (145) (277) (237) 190.23 101.07 55.845 IRON SMIU MI Fe Os Hs Np Ru HASSIUM Actinide Lanthanide Pm NEPTUNIU MP RUTHENIU 93 8 26 61 44 108 76 PROMETHIUM Transition metals Alkaline earth metal Metal Alkali metal M MO (98) (272) VIIB 186.21 238.03 144.24 54.938 U Tc Re Bh Nd Mn URANIU RHENIU BOHRIUM NEODYMIUM 7 25 60 107 92 TECHNETIU M MANGANESE 43 75 VIB (271) 95.95 140.91 231.04 183.84 51.996 W Pr Sg Pa Cr Mo GROUP CAS TUNGSTEN CHROMIUM 91 6 24 74 42 PRASEODYMIUM SEABORGIUM 59 106 PROTACTINIUM MOLYBDENUM M IA VB (268) 1.008 140.12 232.04 180.95 92.906 50.942 V H IOBIU M Ce Ta Th Nb Db CERIUM THORIU M DUBNIU VANADIUM TANTALUM 5 23 HYDROGEN 41 90 73 58 105 1 1 ELEMENT NAME M IVB (267) (227) 138.91 91.224 178.49 47.867 RELATIVE ATOMIC MASS (1) Ti Zr Ac La Rf Hf HAFNIUM ACTINIUM TITANIUM ZIRCONIU MN LANTHANU 89 57 4 22 72 40 104 RUTHERFORDIUM SYMBOL LANTHANIDE ACTINIDE GROUP IUPAC IIIB 44.956 88.906 Y ATOMIC NUMBER Sc TTRIUM PERIODIC TABLE OF THE ELEMENTS 57-71 Actinide 89-103 SCANDIUM Ac-Lr La-Lu 39 3 21 Lanthanide IIA (226) 87.62 40.078 9.0122 137.33 24.305 Sr Be Ba Ca Ra BARIUM RADIUM Mg CALCIUM BERYLLIUM STRONTIU MY MAGNESIUM 88 12 56 2 4 20 38 IA 6.94 (223) 1.008 39.098 132.91 22.990 85.468 H KG Li Fr Cs Na Rb LITHIUM SODIUM CAESIUM RUBIDIUM FRANCIUM GROUP HYDROGE N POTASSIUM 3 37 1 1 11 87 55 19

1 3 2 4 5 6 7

D PERIO

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IX_SCI_EM_Unit-12_CHE.indd 142 09-03-2019 12:21:09 manner. These subshells are designated as 12.2.4 Advantages of the Modern s, p, d, and f. Based on the arrangement of Periodic Table electrons in subshells, the elements of periodic table are classified into four blocks namely s, p, • The table is based on a more fundamental d and f blocks. property i.e., atomic number. • It correlates the position of the element with (1) s-Block Elements: It includes group 1 its electronic configuration more clearly. (alkali metals) and group 2 (alkaline earth metals) elements. They are also called as • The completion of each period is more logical. representative elements. The elements of In a period, as the atomic number increases, group 1 (except hydrogen) are metals. They the energy shells are gradually filled up until react with water to form solutions that an inert gas configuration is reached. change the colour of a vegetable dye from red • It is easy to remember and reproduce. to blue. These solutions are said to be highly • Each group is an independent group and the alkaline or basic. Hence they are called alkali idea of subgroups has been discarded. metals. • One position for all isotopes of an element is justified, since the isotopes have the same The elements of group 2 are also metals. atomic number. They combine with oxygen to form oxides, • The position of the eighth group (in formerly called 'earths', and these oxides Mendeleev‘s table) is also justified in this produce alkaline solutions when they are table. All transition elements have been dissolved in water. Hence, these elements are brought in the middle as the properties of called alkaline earth metals. transition elements are intermediate between (2) p-Block Elements: These elements are left portion and right portion elements of the in group 13 to 18 in the periodic table. They periodic table. include boron, carbon, nitrogen, oxygen, • The table completely separates metals from fluorine families in addition to noble gases nonmetals. The nonmetals are present in (Except helium). They are also called as upper right corners of the periodic table. representative elements. The p-block is • The positions of certain elements which home to the biggest variety of elements were earlier misfit (interchanged) in the and is the only block that contains all three Mendeleev’s periodic table are now justified types of elements: metals, nonmetals, and because it is based on atomic number of the metalloids. elements. (3) d-Block Elements: It includes group 3 • Justification has been offered for placing to group 12 elements. They are found in the lanthanides and actinides at the bottom of the centre of the periodic table. Their properties periodic table. are intermediate to that of s block and p block elements and so they are called transition 12.2.5 Position of hydrogen in elements. the periodic table (4) f – Block Elements: It includes 14 elements Hydrogen is the lightest, smallest and first after (Lanthanum) La (57), called Lanthanoides element of the periodic table. Its electronic and 14 elements after (Actinium) Ac (89), called configuration (1s1) is the simplest of all the Actinoides. They are placed at the bottom of elements. It occupies a unique position in the the periodic table. They are also called as inner periodic table. It behaves like alkali metals as Transition elements. well as halogens in its properties.

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IX_SCI_EM_Unit-12_CHE.indd 143 09-03-2019 12:21:10 Table 12.6 Number of electrons in subshell Shell number (Symbol) 1 (K) 2 (L) 3 (M) 4 (N) Sub shell 1s 2s 2p 3s 3p 3d 4s 4p 4d 4f Maximum number of 2 2 6 2 6 10 2 6 10 14 electrons in each sub shell Maximum number of 2 8 18 32 electrons in each shell

In the periodic table, it is placed at the top (i) Alkali metals. e.g. Lithium to Francium of the alkali metals. (top to bottom) (i) Hydrogen can lose its only electron to form (ii) Alkaline earth metals. e.g: Beryllium to a hydrogen ion (H+) like alkali metals. Radium (top to bottom) (ii) It can also gain one electron to form the (iii) Transition Metals. Group III B to II A hydride ion (H-) like halogens. (iv) P-Block metals. e.g: Al, Ga, In, Tl, Sn, Pb (iii) Alkali metals are solids while hydrogen is a and Bi. gas. 4.3.2. Non-metals Hence the position of hydrogen in the A non-metal is an element that does modern periodic table is still under debate as not have the characters like hardness, shiny, the properties of hydrogen are unique. malleable, suitable and ductile. In other words, 12.2.6. Position of Rare Gases a non-metal is an element that does not have the properties of metal. e.g. All non metals are The elements Helium, Neon, Argon, arranged in P-Block only. P-Block non metals: Krypton, Xenon and Radon of group 18 in C, N O, P, S, Se, Halogen (F, Cl, Br and I) and the periodic table are called as Noble gases or inert gases (Heyo Rn). Rare gases. They are monoatomic gases and do not react with other substances easily, due 12.3.3 Metalloids to completely filled subshells. Hence they are Elements which have the properties of both called as inert gases. They are found in very small metals and non-metals are called as metalloids. quantities and hence they are called as rare gases. (eg) Boron, Arsenic.

12.3 Metals, Non-Metals 12.4 Alloys and Metalloids During 3500 BC(BCE), people used an alloy named 12.3.1 Metals ‘bronze’. The idea of making Metals are typically hard, shiny, malleable an alloy was quite old. The (can be made as sheet), fusible and ductile (can majority of the metallic be drawn into wire) with good electrical and substances used today are thermal conductivity. Except mercury, most alloys. Alloys are mixtures of two or more of the metals are solids at room temperature. metals and are formed by mixing molten metals Metals occupy larger area in the periodic table thoroughly. Rarely nonmetals are also mixed and are categorized as: with metals to produce alloys.

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IX_SCI_EM_Unit-12_CHE.indd 144 09-03-2019 12:21:10 It is generally found that alloying produces Points to Remember a metallic substance that has more useful properties than the original pure metals from ™™ Dobereiner grouped the elements based which it is made. For example, the alloy brass is on their relative atomic masses in a group made from copper and zinc. of three (triads). ™™ John Newlands arranged 56 known 12.4.1 Advantages of alloys elements in the increasing order of their atomic mass. • Alloys do not get corroded or get corroded ™™ Dmitri Mendeleev proposed the law of to very less extent. periodicity. • They are harder and stronger than pure ™™ Mendeleev’s Periodic Table has eight metals (Example: Gold is mixed with vertical columns called ‘groups’ and seven copper and it is harder than pure gold). horizontal rows called ‘period’. • They have less conductance than pure ™™ In the modern periodic table all the metals (Example: Copper is good conductor elements are arranged in the increasing of heat and electricity whereas brass and order of their atomic number. bronze are not good conductors). ™™ There are seven periods and 18 groups in • Some alloys have lower melting point than the periodic table. pure metals (Example: Solder is an alloy ™™ The elements are placed in periods based of lead and tin which has lower melting on the number of shells in their atoms. point than each of the metals). ™™ Based on the common characteristics of • When metal is alloyed with mercury, it is elements in each group, they are grouped called amalgam. as various families.

GLOSSARY Dobereiner’s Law of Triads The atomic mass of the middle element is nearly the same as average of atomic masses of other two elements. Newlands’ Law of Octaves Every eighth element had properties similar to those of the first element like the eighth note in an octave of music is similar to the first. Mendeleev’s Law of Periodicity The physical and chemical properties of elements are the periodic functions of their atomic masses. Modern Periodic Law The chemical and physical properties of elements are the periodic functions of their atomic numbers. Periods Horizontal rows in the modern periodic table. Columns Vertical columns in the modern periodic table s block elements Elements whose valence electrons are added to s subshell. p block elements Elements whose valence electrons are filled in p subshells. d block elements Elements having their valence electrons in the d subshells. f block elements Elements having their valence electrons in the f subshells.

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IX_SCI_EM_Unit-12_CHE.indd 145 09-03-2019 12:21:10 TEXTBOOK EXERCISES

I. Choose the correct answer. 1. If Dobereiner is related with ‘law of triads’, 2. Metals can gain electrons. then Newlands is related with 3. Alloys bear the characteristics of both a) Modern periodic law b) Hund’s rule metals and nonmetals. c) Law of octaves d) Pauli’s Exclusion principle 4. Lanthanides and actinides are kept at 2. Modern periodic law states that the physical the bottom of the periodic table because and chemical properties of elements are the they resemble each other but they do not periodic functions of their resemble with any other group elements. a) atomic numbers b) atomic masses 5. Group 17 elements are named as Halogens. c) similarities d) anomalies V. Assertion and Reason. 3. Elements in the modern periodic table are arranged in groups and periods. Statement: Elements in a group generally a) 7, 18 b) 18, 7 c) 17, 8 d) 8, 17 possess similar properties but elements along a period have different properties. II. Fill in the blanks. Reason: The difference in electronic 1. In Dobereiner’s triads, the atomic weight of configuration makes the element differ in their the middle element is the of the chemical properties along a period. atomic masses of 1st and 3rd elements. a) Statement is true and reason explains the statement. 2. Noble gases belong to group of b) Statement is false but the reason is correct. the periodic table. 3. The basis of the classifications proposed by VI. Answer the following. Dobereiner, Newlands and Mendeleev was 1. State modern periodic law. . 2. What are groups and periods in the modern 4. Example for liquid metal is . periodic table? 3. What are the limitations of Mendeleev's III. Match the following. periodic table? Triads Newlands 4. State any five features of modern periodic Alkali metal Calcium table. Law of octaves Henry Moseley Alkaline earth metal Sodium REFERENCE BOOKS Modern Periodic Law Dobereiner

IV. State whether true or false. If false, 1. CONCISE Inorganic chemistry : 5th Edition ­correct the statement. by J.D. Lee 1. Newlands’ periodic table is based on atomic 2. Inorganic Chemistry by P.L.Soni masses of elements and modern periodic 3. The Periodic table: Its story and its table is based on atomic number of elements. significance: Eric R. Scerri

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IX_SCI_EM_Unit-12_CHE.indd 146 09-03-2019 12:21:10 Concept Map

ICT CORNER Periodic Classification

Steps 1.Type the URL link given below in the browser OR scan the QR code. You can also download the “Royal society of chemistry” mobile app from the given app URL. 2. Click the element from the table and explore the properties of the element you want to learn. 3.On the right top corner click option as shown to learn the uses and properties. 4.For every element we can understand the uses and the properties of elements.

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IX_SCI_EM_Unit-12_CHE.indd 147 09-03-2019 12:21:12