The Periodic Table Lecture Notes 2021 H1 tutor

St Andrew’s Junior College JC1 H1 Chemistry 2021 1 St Andrew’s Junior College H1 Chemistry 2021 Lecture Notes 6 The Periodic Table Assessment Objectives: Trends and variations in atomic and physical properties For elements in the third period (sodium to chlorine), and in Group 17 (chlorine to iodine) candidates should be able to (a) recognise variation in the electronic configurations across a Period and down a Group (b) describe and explain qualitatively the trends and variations in atomic radius, ionic radius, first ionisation energy and electronegativity: (i) across a Period in terms of shielding and nuclear charge (ii) down a Group in terms of increasing number of electronic shells and nuclear charge (c) interpret the variation in melting point and in electrical conductivity acr oss a Period in terms of structure and bonding in the elements (metallic, giant molecular or simple molecular) (d) describe and explain the trend in volatility of the Group 17 elements in terms of instantaneous dipole-induced dipole attraction Trends and variations in chemical properties For elements in the third period (sodium to chlorine) candidates should be able to (e) (i) state and explain the variation in the highest oxidation number of the elements in oxides (for Na2O; MgO; Al2O3; SiO2; P4O10; SO3) and chlorides (for NaCl; MgCl2; AlCl3; SiCl4; PCl5) (ii) state and explain the variation in bonding in oxides and chlorides in terms of electronegativity (with the exception of AlCl3) (iii) describe the reactions of the oxides with water(for Na2O; MgO; Al2O3; SiO2; P4O10; SO3) (iv) describe and explain the acid/base behaviour of oxides (for Na2O; MgO; Al2O3; SiO2; P4O10; SO3) and hydroxides (for NaOH; Mg(OH) 2; Al(OH)3), including, where relevant, am photeric behaviour in reaction with sodium hydroxide (only) and acids. (v) describe and explain the reactions of the chlorides with water (for NaCl; MgCl2; AlCl3; SiCl4; PCl5) (vi) suggest the types of structure and bonding present in the oxides and chlorides from observations of their chemical and physical properties For elements in Group 1 (lithium to caesium) and Group 17 (chlorine to iodine) candidates should be able to (f) describe and explain the relative reactivity of elements of: (i) Group 1 as reducing agents in terms of ease of loss of electron; (ii) Group 17 as oxidising agents in terms of ease of gain of electron (g) describe and explain the trend in thermal stability of Group 17 hydrides in terms of bond energies In addition, candidates should be able to: (h) predict the characteristic properties of an element in a given Group by using knowledge of chemical periodicity (i) deduce the nature, possible position in the Periodic Table, and identity of unknown elements from given information of physical and chemical properties

St Andrew’s Junior College JC1 H1 Chemistry 2021 2 Content: 1. Introduction 2. Variation of Atomic and Physical properties (Also see Atomic Structure & Chemical Bonding) 2.1 Atomic Radius 2.2 Ionic Radius 2.3 First Ionisation Energy 2.4 Electronegativity 2.5 Melting Point 2.6 Electrical Conductivity 3. Variation of Chemical Properties 3.1 Oxidation number of Period 3 oxides and chlorides 3.2 Period 3 oxides and their properties 3.2.1 Bonding 3.2.2 Reaction with water 3.2.3 Acid-base nature of oxides and hydroxides 3.3 Period 3 chlorides and their properties 3.3.1 Bonding 3.3.2 Reaction with water 3.4 Group 1 elements 3.5 Group 17 3.5.1 Group 17 elements 3.5.2 Group 17 hydrides 4. Application of concepts in Periodicity 4.1 Predicting the characteristic properties of an element 4.2 Diagonal relationship in the Periodic Table 4.3 Deducing identity of unknown element from given information 5. Appendix References:  Chemistry in Context by Graham Hill and John Holman  Chemistry in Action by Michael Freemantle Chemguide http://www.chemguide.co.uk/inorganic/period3menu.html

St Andrew’s Junior College JC1 H1 Chemistry 2021 3 1. INTRODUCTION (a) recognise variation in the electronic configurations across a Period and down a Group Elements in the Periodic Table are arranged in increasing order of proton number. The modern Periodic Table is largely based on the works of Dmitri Mendeleev, Lothar Meyer and Henry Moseley. (See Appendix.) The vertical columns are called groups. Elements in the same group have the same number of valence electrons and outer electronic configuration. As such, they show similarities in their physical and chemical properties. The horizontal rows are called periods. Elements in the same period have the same number of filled quantum shells. They have different physical and chemical properties, but there are trends in these properties as we move across the period. The elements are further grouped into four blocks in the periodic table.  s-block [Groups 1 and 2]  p-block [Groups 13 to 18]  d-block [Transition metals] (JC2)  f-block [Lanthanides & Actinides] (not in syllabus) d–block p–block s–block f–block

St Andrew’s Junior College JC1 H1 Chemistry 2021 4 0.00 0.05 0.10 0.15 0.20 0.25 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35 2. VARIATION OF ATOMIC AND PHYSICAL PROPERTIES (b) describe and explain qualitatively the trends and variations in atomic radius, ionic radius, first ionisation energy and electronegativity: (i) across a Period in terms of shielding and nuclear charge (ii) down a Group in terms of increasing number of electronic shells and nuclear charge 2.1 Atomic Radius (refer to Atomic Structure lecture notes) Trend: Atomic radius decreases across the period. Reason: Across a period,  Nuclear charge increases as number of protons increase.  Shielding effect is approximately constant as successive electrons are added to the same quantum shell  Effective nuclear charge increases  Valence electrons are more strongly attracted towards the nucleus Trend: Atomic radius increases down the group. Reason: Down a group,  Although nuclear charge increases as number of protons increase,  the more significant factor is the increased number of filled quantum shells  causing the valence electrons to be further away from the nucleus Proton Number Atomic Radius / nm Li F Na Cl K Sc Zn Br Ga

St Andrew’s Junior College JC1 H1 Chemistry 2021 5 2.2 Ionic Radius (refer to Atomic Structure lecture notes) (a) Cationic radius is smaller than corresponding parent atom Reason:  Nuclear charge remains constant (as number of protons in both the atom and its cation are the same).  The cation has fewer electrons than its atom , thus, the remaining electrons are more strongly attracted to the nucleus.  Furthermore, the cation contains one less filled quantum shell. (b) Anionic radius is greater than corresponding parent atom Reason:  Nuclear charge remains constant (as number of protons in both the a tom and its anion are the same).  The anion has more electrons than protons, thus, the valence electrons are less strongly attracted to the nucleus. (c) Ionic Radius of Isoelectronic Species Trend: Ionic radius of isoelectronic ions decrease across the period. There are 2 sets of isoelectronic ions. Cations: Na+ > Mg2+ > Al3+ > Si4+ [1s2 2s2 2p6] Anions: P3- > S2- > Cl- [1s2 2s2 2p6 3s2 3p6] ratom > rcation ratom < ranion

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