2021 H1 Chemical Bonding Lecture Tutor

St Andrew’s Junior College JC1 H1 Chemistry 2021 1 St Andrew’s Junior College H1 Chemistry 2021 Lecture Notes 3: Chemical Bonding (TUTOR) Assessment Objectives: (a) show understanding that all chemical bonds are electrostatic in nature and describe: (i) ionic bond as the electrostatic attraction between oppositely charged ions; (ii) covalent bond as the electrostatic attraction between a shared pair of electrons and positively charged nuclei, (iii) metallic bond as the electrostatic attraction between a lattice of positive ions and delocalised electrons (b) describe, including the use of ‘dot-and-cross’ diagrams: (i) ionic bonding as in sodium chloride and magnesium oxide (ii) covalent bonding as in hydrogen; oxygen; nitrogen; chlorine; hydrogen chloride; carbon dioxide; methane; ethene (iii) co-ordinate (dative covalent) bonding, as in formation of the ammonium ion and in the Al2Cl6 molecule (c) describe covalent bonding in terms of orbital overlap (limited to s and p orbitals only), giving σ and bonds (see also topic on Introduction to Organic Chemistry) (d) explain the shapes of, and bond angles in, molecules such as BF 3 (trigonal planar); CO 2 (linear); CH 4 (tetrahedral); NH3 (trigonal pyramidal); H 2O (bent); SF 6 (octahedral) by using the Valence Shell Electron Pair Repulsion theory (e) predict the shapes of, and bond angles in, molecules analogous to those specified in (d) (f) explain and deduce bond polarity using the concept of electronegativity [quantitative treatment of electro-negativity is not required] (g) deduce the polarity of a molecule using bond polarity and its molecular shape (analogous to those specified in (d)); (h) describe the following forces of attraction (electrostatic in nature): (i) intermolecular forces, based on permanent and induced dipoles, as in liquid and gaseous CHCl3, Br2 and the noble gases (ii) hydrogen bonding, using ammonia and water as examples of molecules containing –NH and –OH groups (i) outline the importance of intermol ecular forces to the liquefaction of gases when subjected to high pressure and / or low temperature (j) outline the importance of hydrogen bonding to the physical properties of substances, including ice a nd water (k) explain the terms bond energy and bond length for covalent bonds (l) compare the reactivities of covalent bonds in terms of bond energy, bond length and bond polarity

St Andrew’s Junior College JC1 H1 Chemistry 2021 2 (m) describe, in simple terms, the lattice structure of a crystalline solid which is: (i) ionic, as in sodium chloride, magnesium oxide (ii) simple molecular, as in iodine (iii) giant molecular, as in graphite; diamond (iv) hydrogen-bonded, as in ice (v) metallic, as in co