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 proces