NJC 2023 Chemical Bonding Tutorial

National Junior College SH1 H2 Chemistry 1 Success criteria: Relevant Tutorial question What do you still struggle with? Write your queries here. 1. understand that all interatomic bonds and intermolecular forces of attraction are electrostatic in nature and energy is required to overcome them. Thus , the magnitude of the melting/boiling points reflects the strength of the different electrostatic forces of attraction. • describe metallic bond as the electrostatic attraction between a lattice of positive ions and delocalised electrons • describe the metallic lattice structure of a crystalline solid as in copper (see checkpt 5 on pg 18) • describe ionic bond as the electrostatic attraction between oppositely charged ions • describe the ionic lattice structure of a crystalline solid as in NaCl and MgO. See Figures 2.2 under section 2.2 on pg 8. • describe covalent bond as the electrostatic attraction between a shared pair of electrons and positively charged nuclei Q1, Q2 2. describe, interpret and/or predict the effect of different types of structure and bonding on the physical properties of substances. Refer to pg 12 - 18 of lecture notes 3. describe co-ordinate (dative covalent) bonding where both electrons in the covalent bond comes from only one of the bonding atoms. Q3a/ Q9d 4. describe covalent bonding in terms of orbital overlap (use s and p orbitals only), giving σ and π bonds in diatomic molecules. 5. Understand that the pair of orbitals taking part in covalent bonding must either have one unpaired electron each (see section 3.3 on pg 16) or one orbital with lone pair while the other orbital is without electrons (see section 3.2). 6. Covalent bond strength increases with increase in shared electron density between 2 nuclei. See section 3.3 (sigma > pi) and 3.4. (a) bond order (b) effectiveness of orbital overlap. See checkpt 5. Q3b Assess in chemical energetics/ organic chemistry 7. Define the terms ‘Bond energy’ and ‘Bond length’. 8. ‘Bond energy’ and ‘Bond length’ are numerical values that help us compare covalent bond strength. 9. Compare covalent bond strength qualitatively by considering in decreasing order of priority (i) bond order (ii) effectiveness of orbital overlap. See checkpt 5. Q 4 (iii)

National Junior College SH1 H2 Chemistry 2 Refer to pg 19 - 21 of lecture notes 10. describe the lattice structure of a crystalline solid of simple covalent molecule such as iodine and giant molecular lattice (giant covalent lattice) structure of a crystalline solid as in graphite and diamond (see figure 3.5b.1 and 3.5b.2.) see checkpt 6. 11. Able to use the concept of the number orbitals in the valence shell and electronegativity to explain why certain compounds can be formed with period 3 element but not period 2 element. See checkpt 7 Q1 Q6 Refer to pg 22 - 23 of lecture notes for thinking process 12. use of ‘dot -and-cross’ diagrams to describe covalent and ionic bonding Q5 (1st column) Refer to pg 32 - 35, 39 - 40 of lecture notes for thinking process 13. Able to use dot -and-cross diagram and Valence Shell Electron Pair Repulsion theory to identify the different electron geometry of atoms covalently bonded to each other. 14. Able to deduce and compare with reasoning, the shape (molecular geometry) and the bond angle by considering (i) the number of bonding and non -bonding pairs in the electron geometry and (ii) repulsive forces which increase with electron density of the electron pair nearer to the central atom. Q5 (2nd column), Q7, Q8/ Q9 15. explain and deduce bond polarity using the concept of electronegativity [quantitative treatment of electronegativity is not required] 16. deduce the polarity of a molecule using bond polarity and its molecular shape Q 10 Refer to pg 46 thinking processes 17. Describe in words or using suitable diagrams to illustrate the formation of the following intermolecular forces (IMF) i. instantaneous dipole-induced dipole interactions. ii. permanent dipole-permanent dipole interactions between polar molecules. iii. hydrogen bonding between molecules with protonic hydrogen (H directly bonded to N,O and F). 18. For simple covalent molecules, only IMF are overcome during a physical change while interatomic covalent bonds are broken during a chemical change. 19. Strength of Hydrogen bonding > permanent dipole-permanent dipole > instantaneous dipole-induced dipole when molecules of similar Mr are being compared. Q 5 (3 rd column) Q 11/ Q12/ Q 14/ Q16

National Junior College SH1 H2 Chemistry 3 Refer to pg 46 - 49 of lecture notes for the thinking process 20. suggest the type of structure and bonding present in a substance from given information Q4/ Q 13 Q18/ Q19 Refer to pg 54 - 56 of lecture notes for thinking process 21. Dissolution of a solute is energetically favourable if: energy released in the formation of solute-solvent interactions ≥ energy taken in to break the solute- solute and solvent-solvent interactions Q15 22. Able to illustrate ion dipole interaction with one water molecule using a labelled diagram. Q16 Refer to pg 57 23. outline the importance of hydrogen bonding to the physical properties of substances, including ice and water Q 17

National Junior College SH1 H2 Chemistry 4 CHEMICAL BONDING TUTORIAL Interatomic Bonding 1(a) Fill in the following table by matching the following substances to their physical properties. graphite, diamond, copper, iodine, sodium chloride Properties substance structure Describe bonding and relate it to the physical properties (a) A hard and brittle solid. (b) A solid that conducts electricity and melts at 1085oC. (c) A solid that cuts through metal and does not conduct electricity. (d) A substance that sublimates when heated. (e) A solid that can be used as a lubricant.

National Junior College SH1 H2 Chemistry 5 1(b) 2010 MCQ 6 Which diagram best represents the structure of solid magnesium oxide? 1(c) The melting point of calcium, 839oC, is much higher than the melting point of sodium, 98 oC. Which statement is most relevant in explaining the difference? A The calcium atom is larger than the sodium atom. B The calcium atom is heavier than the sodium atom. C The calcium ion, Ca2+, has a higher charge than the sodium ion, Na+. D The calcium ion, Ca2+, contains more electrons than the sodium ion, Na+. 2 Which statement(s) are correct? I HCl (aq) cannot conduct electricity. II Covalent bond is a weak bond compared to ionic bond as boiling point of H 2O is lower than that of MgO. III Ionic bonds and covalent bonds can both occur in the same compound. IV Metals can be distinguished from ionic compounds by their electrical conductivity in the solid state. A Statements I and III are correct. B Statements II and IV are correct. C Statement III and IV are correct. D Statements I, III and IV are correct

National Junior College SH1 H2 Chemistry 6 3(a) Boron trifluoride and ammonia reacts in a 1:1 mole ratio to form a single compound. Describe the type of bond formed during this reaction. 3(b) 2015 MCQ 2 Which row about sigma () bonds and pi () bonds in hydrocarbons is correct? () bonds () bonds A Can be formed by either s or p orbitals Can be formed by either s or p orbitals B Can be formed by either s or p orbitals Can be formed by p orbitals but not s orbitals C Can be formed by p orbitals but not s orbitals Can be formed by either s orbitals but not p orbitals D Can be formed by s orbitals but not p orbitals Can be formed by p orbitals but not s orbitals 4 Explain the following observations. i. Magnesium oxide is used i