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ICSE Notes 2017 : Chemistry - PERIODIC TABLE

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Yasen Ali Syed Shakil
International School, Hyderabad

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1 Chapter-1 PERIODIC TABLE The arrangement of elements in Periodic table made easy to study their properties. The elements are arranged in the increasing order of their atomic numbers. - Atomic number is equal to the number of electrons in the orbits ( or energy shells) of an atom. Modern periodic law - The physical and chemical properties of elements are the periodic functions of their atomic number . Modern Periodic Table has 18 Groups (vertical columns) and 7 Periods (horizontal rows). The elements belonging to a particular group have same number of valence electrons. The period number indicates the number of shells in the atom of an element. Modern Periodic table (Long form of Periodic table) valency No. of valenc e electro ns 1+ 2+ 3+ 4 3- 2- 1- 0 1 2 3 4 5 6 7 8 GROUP NUMBE R IA IIA IIIA IVA VA VIA VIIA 0 1 2 13 14 15 16 17 18 PERIOD 11 shell PERIOD 2 2 shells PERIOD 3 3 shells 3 4 5 6 7 8 9 1 0 1 1 1 2 He2 H- 1 Li 2,1 Be 2,2 Na Mg 2,8,1 B 2,3 2,8,2 C 2,4 N 2,5 O 2,6 Al Si P S 2,8, 3 2,8, 4 2,8, 5 2,8, 6 F 2,7 Ne 2,8 Cl Ar 2,8,7 2,8,8 PERIOD 4 4 shells K Ca 2,8,8 ,1 2,8,8, 2 Br Kr PERIOD 5 Rb Sr I Xe PERIOD 6 Cs Ba At Rn PERIOD 7 Fr Ra ALKAL I META LS ALKALI NE EARTH METAL S TRANSITION ELEMENTS (METALS) HALOGE NS NOB LE GASE S http://icsechemistry16.blogspot.com ICSE CHEMISTRY for Class X www.icsechemistry16.blogspot.com 2 Periodic properties- 1. Ionisation potential (I.P): The minimum amount of energy required to remove a valence electron from an isolated gaseous atom. I.P value is directly proportional to the effect of nucleus on the valence electrons. i.e. I.P value increases with the increase in the nuclear pull over the valence electrons. Helium has the highest ionisation potential value. Across a period: I.P value increases from left to right across a period. ICSE CHEMISTRY for Class X www.icsechemistry16.blogspot.com 3 Reason : As the nuclear pull over valence electron increases across a period require more energy to remove the valence electron. Down a group: I.P value decreases down a group. Reason: As the distance between the Nucleus and the valence shell increases the energy required to remove the valence electron decreases. 2. Electron Affinity (E.A): The amount of energy released when an atom in gaseous state accepts one electron and forms an anion. E.A Value is directly proportional to the tendency of an atom to accept electron i.e the E.A value increases with the tendency to accept electrons. Chlorine has the highest E.A value. Across a Period: The E.A value increases across a period. Reason: The nuclear attraction on the valence electrons increases hence the atom takes the electron more readily. Down a Group: E.A value decreases down a group. Reason: Increase in the atomic radium dominates the tendency to take up the electron. 3. Electronegativity(E.N): The tendency of an atom to attract the bond pair of electrons to itself. E.N value is directly proportional to the nuclear attraction on the valence electron. Fluorine has the highest E.N value. Across a period : The E.N value increases from left to right across a period. Reason: The effect of Nuclear attraction increases on the valence electrons. Across a Group: The E.N value decreases down a group. Reason: The effect of nuclear attraction decreases on the valence electrons. 4. Metal: The element which tends to lose electron/s. Non-metal : The element which gains electron/s. http://icsechemistry16.blogspot.com ICSE CHEMISTRY for Class X www.icsechemistry16.blogspot.com 4 Decreas es ICSE CHEMISTRY for Class X www.icsechemistry16.blogspot.com

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