NJC 2023 Chemical Bonding Tutorial Answer

National Junior College SH1 H2 Chemistry 1 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. NaCl Giant ionic lattice Strong ionic bonds require great amt of energy to overcome. When the regular arrangement of the oppositely charged ions are disrupted, repulsion between like charges causes the lattice to break down. (b) A solid that conducts electricity and melts at 1085oC. Cu Giant metallic structure Strong Metallic bond require great amt of energy to overcome. Sea of delocalised electrons are the mobile charge carriers than enable electrical conductivity. (c) A solid that cuts through metal and does not conduct electricity. Diamond Giant covalent lattice (Giant molecular lattice) Form strong c ovalent bonds with 4 other C atoms in a 3D tetrahedral arrangement, making the lattice very strong. All valence e used for sigma bond formation, absence of mobile charge carriers. (d) A substance that sublimates when heated. I2 Simple molecular structure • Covalent bonding within molecule • Weak intermolecular force of attraction between molecules

National Junior College SH1 H2 Chemistry 2 that can be easily overcome with heat. (e) A solid that can be used as a lubricant. Graphite Giant covalent lattice (Giant molecular lattice) • Forms covalent bond with 3 other C atoms in a 2D network hexagonal carbon rings => graphene layer • Weak intermolecular force of attraction between layers causing the layers to slide over each other easily. 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.

National Junior College SH1 H2 Chemistry 3 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+. Calcium and sodium have giant metallic lattices. Melting point magnitude reflects metallic bond strength. Giant metallic lattice consists of cations in a sea of delocalized electrons, thus metallic bond strength increases with 1) Greater number of valence electrons involved in delocalization. 2) Cation of higher charge over size ratio when factor 1 is the same. Statement C is the answer as it implies that there are greater number of valence electrons involved in the sea of delocalised electrons for calcium than sodium. 2 Which statement(s) are correct? I HCl (aq) cannot conduct