RI 2025 Chemical Bonding 2 Tutorial ans

1 RAFFLES INSTITUTION YEAR 5 H2 CHEMISTRY 2025 Tutorial 8: Chemical Bonding II Answers CH C C H H C C H H H There is no 2sp − 2sp2 overlap since the sp and sp2 C are not next to each other. At the C=C and C≡C bonds, the π bonds are formed by the side-on overlap between the 2p orbitals of C. The 1s and 2sp overlap occur between the triple bonded C and the H atom which uses its 1s orbitals for σ bond with the 2sp hybrid orbital of C. Answer: C 2. H3C C C CH2 4 3 2 1 OH The terminal carbon atoms (1 and 4) are sp3 and not sp2 hybridised. Hence option C is not correct and so is the answer. Answer: C 3. (a) (b) A σ–bond is formed when valence orbitals overlap head–on while a π–bond is formed when valence orbitals overlap side–on. In ethene, the two carbon atoms form a σ–bond via the head–on overlapping of two sp 2 hybrid orbitals i.e. In ethene, the two carbon atoms also form a π–bond via the side–on overlapping of the two unhybridised p orbitals i.e. (c) sp2 hybridisation (d) 3 sp2 orbitals (each with one small and one large lobe): 120o 120o 120o 120o sp2 hybrid orbitals σ bond p orbitals π bond 2sp 2sp 2sp3 2sp2 2sp2 1. sp3 sp sp sp3 sp3

2 4. (a) (b) BeF2 F Be F sp hybridisation [BeF4]2− Be F F F F 2− sp3 hybridisation 5. (a) (b) Shape: Bent O-N-O Bond angle: 115° (Any answer between 109.5o and 120o is acceptable) (c) sp2. (d) The unhybridised p orbital of N and p orbitals of the O atoms are perpendicular to the plane of the ion (containing σ bonds). These p orbitals overlap side-on continuously, so that the π electrons are delocalised over the N and O atoms. Thus, NO2− exhibits resonance and the two N–O bonds are equivalent, with the same bond length. N O O − N− O O N OO 6. (a) (b) It is expected that BN is an electrical conductor due to the delocalistion of π electrons from the continuous side- on overlap of p orbitals . However, since N is more electronegative than B, the π electrons tend to stay with N rather than delocalise throughout the π -electron cloud. Hence, BN is a poorer electrical conductor than graphite. B N BN B N B N BN N B N B N B N B N N BN B N B N B 109.5o N − Both B and N are sp2 hybridised and each B and N atom has an unhybridised p orbital perpendicular to the plane of atoms. Each B atom forms 3 σ bonds with 3 N atoms and each N atom also forms 3 σ bonds with 3 B atoms. B is from Group 13 and its unhybridised p orbital is empty while N is from Group 15 and its unhybridised p orbital has 2 electrons. The unhybridised p orbitals overlap side -on continuously with its neighbours resulting in the delocalisation of π electrons over the whole layer.