SESSION 2023/2024 TOPIC 4: CHEMICAL BONDING CHEMISTRY SK015 47 SUGGESTED ANSWER FOR TUTORIAL 4.0 4.1: Lewis Structure 1. Complete the table below: Element Li Be B C N O Cl Ne No. of Valence Electron 1 2 3 4 5 6 7 8 Lewis dot symbol Li Be B C N O F Ne 2. a) Define Octet rule states that atoms tend to form bonds to obtain 8 electrons in the valence shell. b) electronic configuration and type of stability i. O : 1s 2 2s 2 2p 4 O2- : 1s 2 2s 2 2p 6 (noble gas configuration) ii. Mg : 1s 2 2s 2 2p 6 3s 2 Mg2+ : 1s 2 2s 2 2p 6 (noble gas configuration) iii. Mn : 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 5 Mn2+ : 1s 2 2s 2 2p 6 3s 2 3p 6 3d 5 (half-filled orbital configuration) iv. Zn : 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 10 Zn2+ : 1s 2 2s 2 2p 6 3s 2 3p 6 3d 10 (pseudo-noble gas configuration) 3. a) i. define Ionic bond is the strong electrostatic force between positive and negative ions that hold them together in solid crystals. ii. formation of ionic bond in Na2O. Na2O : Na has 1 valence electron, while O has 4 valence electrons Na loses 1 electron and forms Na+ ion, while O accepts the electrons to form O2- ion. Electrostatic force between Na+ ion and O2- ion form ionic bond. Na Na + Na + 2- O 2 O b) i. covalent bond Covalent bond is formed by a pair of electrons shared between two atoms. Atoms in covalent bond are held by electrostatic forces between the shared electron and the nuclei of the atom involved.
SESSION 2023/2024 TOPIC 4: CHEMICAL BONDING CHEMISTRY SK015 48 ii. formation of covalent bond in CF4 CF4 : C has 4 Valence electrons, while F has 7 Valence electrons. Thus C shared its valence electrons with F in order to form covalent bond. + C + + F + F F F C F F F F c) i. Differences ii. formation of dative bond in NH4 + H N + H H H + H N H H H + 4. Lewis structure and type of octet a) BeCl2 d) SO2 Cl Be Cl O S O Incomplete octet Octet b) CO2 e) NO2 O C O Octet Odd number electron c) BF3 f) CH3Cl F B F F H C H H Cl Incomplete octe Octet Covalent bond Dative bond Covalent bond is formed when two atoms share one or more electron pairs. a bond in which the pair of shared electrons is supplied by one of the two bonded atoms. O N O -
SESSION 2023/2024 TOPIC 4: CHEMICAL BONDING CHEMISTRY SK015 49 g) PCl5 j) XeF4 Expanded octet Expanded octet h) SF4 k) CO3 2- F S F F F Expanded octet Octet i) SF6 l) NO2 + F S F F F F F Expanded octet Octet 5. Lewis structure C2H6 C2H4 C C H H H H H H C C H H H H Bond length C2H6 has longer C-C bond than C2H4. 6. a) possible structures and formal charge S C S 0 0 0 A B S C S 0 -1 +1 most plausible structure. Structure A is the most plausible structure because the formal charge for each atom is zero. Cl P Cl Cl Cl Cl F Xe F F F 2- O C O O O N O +
SESSION 2023/2024 TOPIC 4: CHEMICAL BONDING CHEMISTRY SK015 50 b) possible structures and formal charge N C O 0 -1 0 A B N C O 0 -2 +1 C N C O 0 0 -1 most plausible structure. Structure C is the most plausible structure because the negative formal charge is on more electronegative atom, O. 7. a) definition resonance structures Lewis structure having same arrangement of atoms but differ in the position of their electrons b) resonance structures of the O3 and NO3 − . O3 O O + O O O + O NO3 − - O N O O - O N O O - O N O O 4.2: Molecular Shape and Polarity 1. a) definition Valence Shell Electron-pair Repulsion (VSEPR) theory state that electron pairs around the central atom is located as far as possible from the others in order to minimize the repulsions. b) i) All molecules has 4 electron pairs around their central atom. Therefore, Electron pair arrangement for all molecule: tetrahedral CH4 • 4 Bonding pair and no lone pair • Based on VSEPR theory, the valence electron pairs around central atom are oriented as far as possible to minimize the repulsion between them. • The strength of electron repulsion of Bonding Pair-Bonding Pair are equals. • Molecular geometry: tetrahedral • The H-N-H angle: 109.5o . NH3 • 3 Bonding pair and 1 lone pair • Based on VSEPR theory, the valence electron pairs around central atom are oriented as far as possible to minimize the repulsion between them. • The strength of electron repulsion are Lone Pair-Bonding Pair > Bonding PairBonding Pair. • Molecular geometry: trigonal pyramidal • The H-N-H angle: 107.3o . • H2O
SESSION 2023/2024 TOPIC 4: CHEMICAL BONDING CHEMISTRY SK015 51 • 2 Bonding pair and 2 lone pair • Based on VSEPR theory, the valence electron pairs around central atom are oriented as far as possible to minimize the repulsion between them. • The strength of electron repulsion are Lone Pair-Lone Pair > Lone Pair-Bonding Pair > Bonding Pair-Bonding Pair. • Molecular geometry: bent • The H-N-H angle: 104.5o . ii) SiF4 • 4 electron pairs around central atom. • Electron pair arrangement: tetrahedral • 4 Bonding pair and no lone pair • Based on VSEPR theory, the valence electron pairs around central atom are oriented as far as possible to minimize the repulsion between them. • The strength of electron repulsion of Bonding Pair-Bonding Pair are equals. • Molecular geometry: tetrahedral SF4 • 5 electron pairs around central atom. • Electron pair arrangement: trigonal bipyramidal • 4 Bonding pair and 1 lone pair • Based on VSEPR theory, the valence electron pairs around central atom are oriented as far as possible to minimize the repulsion between them. • The strength of electron repulsion are Lone Pair-Bonding Pair > Bonding PairBonding Pair. • Molecular geometry: see-saw 2. a) Definition dipole moment. Product of the positive charge and distance between the charges. (Dictionary of chemistry) b) factors that affect the polarity of a molecule. • Molecular geometry • Electronegativity of bonded atom c) Explanation • Bond between C-Cl is polar. • The atoms in CCl4 are arrange symmetrically in tetrahedral shape. • The bond dipoles of CCl4 may cancel each other. • Net charge = 0. 3. state molecular geometries, and determine polarity a) BeCl2 Cl Be Cl • Molecular geometry: linear Cl Be Cl • Cl is more electronegative than Be. Bond between Be-Cl is polar. • The dipole moment can cancel each other. equal to 0. • Non-Polar
SESSION 2023/2024 TOPIC 4: CHEMICAL BONDING CHEMISTRY SK015 52 b) CO2 O C O • Molecular geometry: linear • O is more electronegative than C. Bond between C-O is polar. • The dipole moment can cancel each other. equal to 0. • Non-Polar c) BF3 F B F F • Molecular geometry: trigonal planar F B F F • F is more electronegative than B. Bond between B-F is polar. • The dipole moment can cancel each other. equal to 0. • Non-Polar d) SO2 O S O • Molecular geometry: V-shaped S O O • O is more electronegative than S. Bond between S-O is polar. • The dipole moment cannot cancel each other. not equal to 0. • Polar e) NO2 O N O - • Molecular geometry: V- shaped N O O • O is more electronegative than N. Bond between N-O is polar. • The dipole moment cannot cancel each other. not equal to 0. • Polar f) CH3Cl H C H H Cl • Molecular geometry: tetrahedral
SESSION 2023/2024 TOPIC 4: CHEMICAL BONDING CHEMISTRY SK015 53 H C H H Cl • Electronegative of Cl > C > H. Bond between C-H and C-Cl is polar. • The dipole moment cannot cancel each other. does not equal to 0. • Polar g) PCl5 Cl P Cl Cl Cl Cl • Molecular geometry: trigonal bipyramidal Cl P Cl Cl Cl Cl • Cl is more electronegative than P. Bond between P-Cl is polar. • The dipole moment can cancel each other. equal to 0. • Non-Polar h) SF4 F S F F F • Molecular geometry: see-saw S F F F F • F is more electronegative than S. Bond between S-F is polar. • The dipole moment can not cancel each other. not equal to 0. • Polar i) SF6 F S F F F F F • Molecular geometry: octahedral F S F F F F F
SESSION 2023/2024 TOPIC 4: CHEMICAL BONDING CHEMISTRY SK015 54 • F is more electronegative than S. Bond between S-F is polar. • The dipole moment can cancel each other. equal to 0. • Non-Polar j) XeF4 F Xe F F F • Molecular geometry: square planar F Xe F F F • F is more electronegative than Xe. Bond between Xe-F is polar. • The dipole moment can cancel each other. equal to 0. • Non-Polar 4.3: Orbital Overlap and Hybridisation 1. a) Define Valence bond theory state that a covalent bond is formed when neighbouring atomic orbitals overlaps. b) formation of sigma and pi bonds. Sigma bond: Overlapping of orbitals end to end. Pi bond: Overlapping of orbitals side to side. c) formation of bond in O2. O O 1 σ bond, 1 π bonds Valence orbital diagram; O: 2s 2p
SESSION 2023/2024 TOPIC 4: CHEMICAL BONDING CHEMISTRY SK015 55 • 2p orbitals consist of 2 unpaired electrons. • The 2p orbitals of an oxygen atom will overlap with 2p orbitals of another O atom to form 1 σ bond and 1 π bonds. Orbital overlapping diagram; O O 2. a) definition hybridisation of atomic orbitals Mixing of atomic orbitals in an atom to generate new set of orbitals. b) type of hybridisation C C H H C H C N H H sp 2 sp 2 sp 3 sp c) hybridisation of the underlined atoms i. BF3 sp2 ii. CCl4 sp3 3. Type of hybridisation and orbital overlapping diagram a) BeH2 H Be H • 2 Bonding pair and no lone pair • Type of hybrid: sp Valence orbital diagram, Be (ground state): H (ground state): 2s 2p 1s Be (excited state): 2s 2p Be (hybrid): sp 2p
SESSION 2023/2024 TOPIC 4: CHEMICAL BONDING CHEMISTRY SK015 56 Orbital overlapping diagram; H H Be sp sp b) BH3 H B H H • 3 Bonding pair and no lone pair • Type of hybrid: sp2 Valence orbital diagram, B (ground state): H (ground state): 2s 2p 1s B (excited state): 2s 2p B (hybrid): sp 2 2p Orbital overlapping diagram; H H H sp 2 sp 2 sp 2 B c) PCl5 Cl P Cl Cl Cl Cl • 5 Bonding pair and no lone pair • Type of hybrid: sp3d Valence orbital diagram, P (ground state):
SESSION 2023/2024 TOPIC 4: CHEMICAL BONDING CHEMISTRY SK015 57 3s 3p 3d P (excited state): 3s 3p 3d P (hybrid): sp 3 d 3d Cl (ground state): 3s 3p Orbital overlapping diagram; sp 3 d sp 3 d sp 3 d sp 3 d sp 3 d Cl P Cl Cl Cl Cl 3p 3p 3p 3p 3p d) SeF4 F Se F F F • 4 Bonding pair and 1 lone pair • Type of hybrid: sp3d Valence orbital diagram, Se (ground state): F (ground state): 4s 4p 4d 2s 2p Se (excited state): 4s 4p 4d
SESSION 2023/2024 TOPIC 4: CHEMICAL BONDING CHEMISTRY SK015 58 Se (hybrid): sp 3 d 4d Orbital overlapping diagram; sp 3 d sp 3 d sp 3 d sp 3 d sp 3 d Se F F F F 2p 2p 2p 2p e) SCl6 Cl S Cl Cl Cl Cl Cl • 6 Bonding pair and no lone pair • Type of hybrid: sp3d 2 Valence orbital diagram, S (ground state): Cl (ground state): 3s 3p 3d 3s 3p S (excited state): 3s 3p 3d S (hybrid): sp 3 d 2 3d
SESSION 2023/2024 TOPIC 4: CHEMICAL BONDING CHEMISTRY SK015 59 Orbital overlapping diagram; sp 3 d 2 sp 3 d 2 sp 3 d 2 sp 3 d 2 sp 3 d 2 P Cl Cl Cl Cl Cl 3p 3p 3p 3p 3p sp 3 d 2 Cl 3p S f) ICl2 − Cl I Cl - • 2 Bonding pair and 3 lone pair • Type of hybrid: sp3d Valence orbital diagram, I − (ground state): Cl (ground state): 5s 5p 5d 3s 3p I − (excited state): 5s 5p 5d I − (hybrid): sp 3 d 5d Orbital overlapping diagram; sp 3 d sp 3 d sp 3 d sp 3 d sp 3 d I - Cl Cl 3p 3p
SESSION 2023/2024 TOPIC 4: CHEMICAL BONDING CHEMISTRY SK015 60 g) ICl4 + Cl I Cl Cl Cl + • 4 Bonding pair and 1 lone pair • Type of hybrid: sp3d Valence orbital diagram, I + (ground state): Cl (ground state): 5s 5p 5d 3s 3p I + (excited state): 5s 5p 5d I + (hybrid): sp 3 d 5d Orbital overlapping diagram; sp 3 d sp 3 d sp 3 d sp 3 d sp 3 d I + Cl Cl Cl Cl 2p 2p 2p 2p 4.4: Intermolecular Forces 1. a) Attractive force between polar molecule • Polar molecule attract each other via dipole-dipole forces. • When partial +ve charge of one molecule nears the partial –ve charge on another molecule, they attract each other and form dipole-dipole forces. b) London dispersion forces • When molecules are very close to each other, the London Dispersion Forces is significant because electrons repel one another. • The motion of electrons in one atom influence the motions of electrons in neighboring atom. • Thus, the temporary dipole of 1 atom can induce a similar dipole of an adjacent atom causing the atoms to attract to each other forming London dispersion forces.
SESSION 2023/2024 TOPIC 4: CHEMICAL BONDING CHEMISTRY SK015 61 c) type of van der Waals forces i. Cl2 London Dispersion Forces i. PCl3 dipole-dipole forces and London Dispersion Forces iii. H2S dipole-dipole forces and London Dispersion Forces iv. CCl4 London Dispersion Forces 2. a) factors that influence the strength of van der Waals forces. Molecular size, and polarity of molecules. b) i. Boiling point of ICl > Br2 • ICl is polar, Br2 is non-polar. • Intermolecular forces between Br2 molecules is London Dispersion Forces. • Intermolecular forces between ICl molecules is dipole-dipole forces. • dipole-dipole forces stronger than London Dispersion Forces. ii. Boiling point of I2 > Br2 • Molecular weight of I2 > Br2. • Strength of van der Waals forces between I2 molecules > Br2. iii. Boiling point of HBr > CF4 • HBr is polar, CF4 is non-polar. • Intermolecular forces between CF4 molecules is London Dispersion forces. • Intermolecular Forces between HBr molecules is dipole-dipole forces. • dipole-dipole forces stronger than London Dispersion Forces. 3. a) describe HBond and explain factors that influence the hydrogen bond. • Attractive forces between H which is covalently bonded to highly electronegative atom (F, O, N) in one molecule and highly electronegative atom (F,O,N) in another atom. • Factors that influences the strength of hydrogen bond is electronegativity of F, O, and N. Higher the electronegativity, the stronger the hydrogen bond. b) i. Boiling point of H2O > CH4 • H2O can form Hydrogen Bond between molecules. • CH4 can only form van der Waals forces. • Hydrogen Bond stronger than van der Waals forces. ii. Boiling point of H2O > NH3 • O is more electronegative than N. • Strength of Hydrogen Bond between H2O molecules > between NH3 molecule. 4. Boiling point of ethanol > dimethyl ether. • Ethanol can form Hydrogen Bond. • Dimethyl ether can only form van der Waals forces. • Hydrogen bond stronger than van der Waals forces.
SESSION 2023/2024 TOPIC 4: CHEMICAL BONDING CHEMISTRY SK015 62 5. a) The band energy gap is the energy gap between a fully occupied valence band and an empty conduction band. b) In conductors, the valence and conduction bands overlap each other. In insulators, there is large energy gap between valence and conduction bands, while in semiconductors this energy gap is small, so that electrons can make the jump up to the conductions band. 6. a) Electron sea model Al3+ e e e e e e e e e e e e e e e e e e e e e e e e Al3+ Al3+ Al3+ Al3+ Al3+ Al3+ Al3+ Al3+ Al3+ Al3+ Al3+ e e e e e e e e e e e e • When Al atoms are arrange closely packed to each other, each of Al atom will released its valence electrons and forming sea of delocalized electrons and Al3+ ions. • The attractive forces between Al3+ ions and sea of electrons forming metallic bond. b) i. Boiling point Be > Mg. • Size of Be2+ < Mg2+ . • Strength of metallic bond Be > Mg. • Energy needed to break the metallic bond in Be > Mg. ii. Boiling point Al > Mg. • Size of Al3+ < Mg2+ . • Al has greater number of valence electrons than Mg. • Strength of metallic bond Al > Mg. • Energy needed to break the metallic bond in Al > Mg.
SESSION 2023/2024 TOPIC 4: CHEMICAL BONDING CHEMISTRY SK015 63 MEKA 4 1. a) Lewis dot symbol i. H ii. O iii. Al b) formation bond i. Al2O3: Al has 3 Valence electrons, while O has 6 Valence electrons. Al loses 3 electrons and form Al3+ ion, while O accept the electrons to form O2- ion. Electrostatic force between Al3+ ion and O2- ion form ionic bond. Al + O Al 3+ O 2- 3 Al O O 2 ii. H2O: O has 6 Ve, while H has 1 Ve Oxygen will share its 2 valence electrons with two H. Electrostatic force between nucleus of atom and electrons shared form covalent bond. H + O + H H O H iii. + H H O + + H H O H H 2. Lewis structure a) SeF4 b) AlBr3 F Se F F F Br Al Br Br Expanded octet Incomplete octet c) NO3 - d) CCl2F2 O N O O - F C Cl F Cl Octet Octet e) NO2 + f) NO O N O + N O Octet Odd number electron
SESSION 2023/2024 TOPIC 4: CHEMICAL BONDING CHEMISTRY SK015 64 3. CO2 a) Possible Lewis structure O C O O C O A B b) Formal Charge O C O O C O A B +1 0 -1 0 0 0 c) Most plausible structure Structure B is most stable because formal charge of each atom equals to zero. OCS a) Possible Lewis structure O C S O C S A B O C S C b) Formal Charge O C S O C S A B O C S C +1 0 -1 0 0 0 -1 0 +1 c) Most plausible structure Structure B is the most stable because formal charge of each atom equals to zero. N3 - a) Possible Lewis structure N N N N N N A B - - b) Formal Charge N N N N N N A B - 0 +1 - -2 -1 +1 -1 c) Most plausible structure Structure B is most stable because formal charge of each atoms nearer to zero. 4. resonance a) O3 O O O O O O b) NO2 + O N O O N O O N O + + +
SESSION 2023/2024 TOPIC 4: CHEMICAL BONDING CHEMISTRY SK015 65 5. a) i. Valence Shell Electron-pair Repulsion (VSEPR) theory state that electron pairs around the central atom is located as far as possible from the others in order to minimize the repulsions. ii. The strength of repulsion between lone pair-lone pair > lone pair – bonding pair > bonding pair – bonding pair. b) CO2 i. Lewis structure O C O iii. electron pair arrangement : linear iii. number of bonding pair: 2 number of lone pair : 0 iv. Bonding pair-bonding pair repulsion are equal. v. Molecular geometry: Linear O C O vi. Bond angle: 180o vii. Electronegativity • O is more electronegative than C • O-C bond is polar viii. Polarity • Bond dipole can cancel each other, μ=0. • Non-Polar. HCl i. Lewis structure H Cl ii. Molecular geometry: Linear H Cl iii. Electronegativity • Cl is more electronegative than H • H-Cl bond is polar BF3 i. Lewis structure F B F F ii. electron pair arrangement : trigonal planar iii. number of bonding pair: 3 number of lone pair : 0 iv. Bonding pair-bonding pair repulsion are equal. v. Molecular geometry: trigonal planar
SESSION 2023/2024 TOPIC 4: CHEMICAL BONDING CHEMISTRY SK015 66 F B F F vi. Bond angle: 120 o vii. Electronegativity • F is more electronegative than B • B-F bond is polar viii. Polarity • Bond dipole can cancel each other, μ=0. • Non-Polar. SnCl2 *correction on question 5(b) i. Lewis structure Cl Sn Cl ii. electron pair arrangement : trigonal planar iii. number of bonding pair: 2 number of lone pair : 1 iv. lone pair-bonding pair repulsion > bonding pair-bonding pair repulsion. v. Molecular geometry: bent Sn Cl Cl vi. Bond angle: <120o vii. Electronegativity • Cl is more electronegative than Sn • Sn-Cl bond is polar viii. Polarity • Bond dipole cannot cancel each other, μ≠0. • Polar. SO2 i. Lewis structure O S O ii. electron pair arrangement : trigonal planar iii. number of bonding pair: 2 number of lone pair : 1 iv. lone pair-bonding pair repulsion > bonding pair-bonding pair repulsion. v. Molecular geometry: bent S O O
SESSION 2023/2024 TOPIC 4: CHEMICAL BONDING CHEMISTRY SK015 67 vi. Bond angle: <120o vii. Electronegativity • O is more electronegative than S • S-O bond is polar viii. Polarity • Bond dipole cannot cancel each other, μ≠0. • Polar. CCl4 i. Lewis structure Cl C Cl Cl Cl ii. electron pair arrangement : tetrahedral iii. number of bonding pair: 4 number of lone pair : 0 iv. Bonding pair-bonding pair repulsion are equal. v. Molecular geometry: tetrahedral C Cl Cl Cl Cl vi. Bond angle: 109.5o vii. Electronegativity • Cl is more electronegative than C • C-Cl bond is polar viii. Polarity • Bond dipole can cancel each other, μ=0. • Non Polar. CH2Cl2 i. Lewis structure Cl C Cl H H ii. electron pair arrangement : tetrahedral iii. number of bonding pair: 4 number of lone pair : 0 iv. Bonding pair-bonding pair repulsion are equal. v. Molecular geometry: tetrahedral
SESSION 2023/2024 TOPIC 4: CHEMICAL BONDING CHEMISTRY SK015 68 C H H Cl Cl vi. Bond angle: 109.5o vii. Electronegativity • Cl is more electronegative than C • C-Cl bond is polar viii. Polarity • Bond dipole cannot cancel each other, μ≠0. • Polar. NF3 i. Lewis structure F N F F ii. electron pair arrangement : tetrahedral iii. number of bonding pair: 3 number of lone pair : 1 iv. Lone pair-bonding pair repulsion > Bonding pair-bonding pair repulsion. v. Molecular geometry: trigonal pyramidal N F F F vi. Bond angle: <109.5o vii. Electronegativity • F is more electronegative than N • N-F bond is polar viii. Polarity • Bond dipole cannot cancel each other, μ≠0. • Polar. H2O i. Lewis structure H O H ii. electron pair arrangement : tetrahedral iii. number of bonding pair: 2 number of lone pair : 2 iv. lone pair-lone pair repulsion > Lone pair-bonding pair repulsion > Bonding pairbonding pair repulsion. v. Molecular geometry: bent
SESSION 2023/2024 TOPIC 4: CHEMICAL BONDING CHEMISTRY SK015 69 O H H vi. Bond angle: 104.5o vii. Electronegativity • O is more electronegative than H • O-H bond is polar viii. Polarity • Bond dipole cannot cancel each other, μ≠0. • Polar. PCl5 i. Lewis structure Cl P Cl Cl Cl Cl ii. electron pair arrangement : trigonal bipyramidal iii. number of bonding pair: 5 number of lone pair : 0 iv. Bonding pair-bonding pair repulsion are equals. v. Molecular geometry: trigonal bipyramidal P Cl Cl Cl Cl Cl vi. Bond angle: 120o , 90o vii. Electronegativity • Cl is more electronegative than P • P-Cl bond is polar viii. Polarity • Bond dipole can cancel each other, μ=0. • Non Polar. SF4 i. Lewis structure F S F F F ii. electron pair arrangement : trigonal bipyramidal iii. number of bonding pair: 4 number of lone pair : 1
SESSION 2023/2024 TOPIC 4: CHEMICAL BONDING CHEMISTRY SK015 70 iv. lone pair-bonding pair repulsion > Bonding pair-bonding pair repulsion. v. Molecular geometry: see-saw S F F F F vi. Bond angle: <120o , <90o vii. Electronegativity • F is more electronegative than S • S-F bond is polar viii. Polarity • Bond dipole cannot cancel each other, μ≠0. • Polar. ICl3 i. Lewis structure Cl I Cl Cl ii. electron pair arrangement : trigonal bipyramidal iii. number of bonding pair: 3 number of lone pair : 2 iv. lone pair-lone pair repulsion > lone pair-bonding pair repulsion > Bonding pairbonding pair repulsion. v. Molecular geometry: T-shape I Cl Cl Cl vi. Bond angle: 90o vii. Electronegativity • Cl is more electronegative than I • I-Cl bond is polar viii. Polarity • Bond dipole cannot cancel each other, μ≠0. • Polar. XeF2 i. Lewis structure F Xe F ii. electron pair arrangement : trigonal bipyramidal
SESSION 2023/2024 TOPIC 4: CHEMICAL BONDING CHEMISTRY SK015 71 iii. number of bonding pair: 2 number of lone pair : 3 iv. lone pair-lone pair repulsion > lone pair-bonding pair repulsion > Bonding pairbonding pair repulsion. v. Molecular geometry: linear Xe F F vi. Bond angle: 180 o vii. Electronegativity • F is more electronegative than Xe • Xe-F bond is polar viii. Polarity • Bond dipole cannot cancel each other, μ≠0. • Polar. SF6 i. Lewis structure F S F F F F F ii. electron pair arrangement : Octahedral iii. number of bonding pair: 6 number of lone pair : 0 iv. Bonding pair-bonding pair repulsion are equals. v. Molecular geometry: octahedral S F F F F F F vi. Bond angle: 90o vii. Electronegativity • F is more electronegative than S • S-F bond is polar viii. Polarity • Bond dipole can cancel each other, μ=0. • Non Polar.
SESSION 2023/2024 TOPIC 4: CHEMICAL BONDING CHEMISTRY SK015 72 BrF5 i. Lewis structure Br F F F F F ii. electron pair arrangement : Octahedral iii. number of bonding pair: 5 number of lone pair : 1 iv. Lone pair-bonding pair repulsion > Bonding pair-bonding pair repulsion. v. Molecular geometry: square pyramidal Br F F F F F vii. Bond angle: <90o vii. Electronegativity • F is more electronegative than Br • Br-F bond is polar viii. Polarity • Bond dipole cannot cancel each other, μ≠0. • Polar. XeF4 i. Lewis structure Xe F F F F ii. electron pair arrangement : Octahedral iii. number of bonding pair: 4 number of lone pair : 2 iv. Lone pair-lone pair repulsion > Lone pair-bonding pair repulsion > Bonding pair-bonding pair repulsion. v. Molecular geometry: square planar Xe F F F F viii. Bond angle: 90o vii. Electronegativity • F is more electronegative than Xe • Xe-F bond is polar
SESSION 2023/2024 TOPIC 4: CHEMICAL BONDING CHEMISTRY SK015 73 viii. Polarity • Bond dipole can cancel each other, μ=0. • Non Polar. 6. a) i. Valence bond theory state that a covalent bond is formed when neighbouring atomic orbitals overlapped . ii. sigma bond is formed when atomic orbitals is overlap end-to-end while pi bond is formed when atomic orbitals is overlap sideways. b) Shape of orbital hybrid i. sp sp sp ii. sp2 sp 2 sp 2 sp 2 iii. sp3 sp 3 sp 3 sp 3 sp 3 iv. sp3d sp 3 d sp 3 d sp 3 d sp 3 d sp 3 d v. sp3d 2 sp 3 d 2 sp 3 d 2 sp 3 d 2 sp 3 d 2 sp 3 d 2 P sp 3 d 2 c) BeCl2 i. & ii. Lewis structure & formal charge Cl Be Cl 0 0 0 iii. number of bonding pair : 2 number of lone pair:0
SESSION 2023/2024 TOPIC 4: CHEMICAL BONDING CHEMISTRY SK015 74 iv. molecular geometry: linear Cl Be Cl v. valence orbital diagram Be (ground state): 2s 2p Be (excited state): 2s 2p Be (hybrid): sp 2p Cl (ground state): 3s 3p vi. orbital overlapping diagram sp sp Cl Cl 3p 3p Be C2H2 i. & ii. Lewis structure & formal charge H C C H 0 0 0 0 iii. number of bonding pair : 2 number of lone pair:0 iv. molecular geometry: linear H C C H v. valence orbital diagram C (ground state): 2s 2p C (excited state): 2s 2p C (hybrid): sp 2p
SESSION 2023/2024 TOPIC 4: CHEMICAL BONDING CHEMISTRY SK015 75 H (ground state): 1s vi. orbital overlapping diagram H H C sp sp sp sp C 2p 2p 2p 2p AlCl3 i. & ii. Lewis structure & formal charge Cl Al Cl Cl 0 0 0 0 iii. number of bonding pair : 3 number of lone pair:0 iv. molecular geometry: trigonal planar Cl Al Cl Cl v. valence orbital diagram Al (ground state): 3s 3p Al (excited state): 3s 3p Al (hybrid): sp 2 3p Cl (ground state): 3s 3p
SESSION 2023/2024 TOPIC 4: CHEMICAL BONDING CHEMISTRY SK015 76 vi. orbital overlapping diagram sp 2 sp 2 sp 2 Al Cl Cl Cl 3p 3p 3p CH2O i. & ii. Lewis structure & formal charge H C H O 0 0 0 0 iii. number of bonding pair : 3 number of lone pair:0 iv. molecular geometry: trigonal planar O C H H v. valence orbital diagram C (ground state): 2s 2p C (excited state): 2s 2p C (hybrid): sp 2 2p O (ground state): 2s 2p O (excited state): 2s 2p O (hybrid state): sp 2 2p
SESSION 2023/2024 TOPIC 4: CHEMICAL BONDING CHEMISTRY SK015 77 H (ground state): 1s vi. orbital overlapping diagram sp 2 sp 2 sp 2 C H 2p 2p sp 2 sp 2 sp 2 O H 1s 1s CCl4 i. & ii. Lewis structure & formal charge Cl C Cl Cl Cl 0 0 0 0 0 iii. number of bonding pair : 4 number of lone pair:0 iv. molecular geometry: tetrahedral Cl C Cl Cl Cl v. valence orbital diagram C (ground state): 2s 2p C (excited state): 2s 2p C (hybrid): sp 3
SESSION 2023/2024 TOPIC 4: CHEMICAL BONDING CHEMISTRY SK015 78 Cl (ground state): 3s 3p vi. orbital overlapping diagram sp 3 sp 3 sp 3 P Cl Cl Cl Cl 3p 3p 3p 3p sp C 3 NF3 i. & ii. Lewis structure & formal charge F N F F 0 0 0 0 iii. number of bonding pair : 3 number of lone pair:1 iv. molecular geometry: trigonal pyramidal F N F F v. valence orbital diagram N (ground state): 2s 2p N (excited state): 2s 2p N (hybrid): sp 3 F (ground state): 2s 2p
SESSION 2023/2024 TOPIC 4: CHEMICAL BONDING CHEMISTRY SK015 79 vi. orbital overlapping diagram sp 3 sp 3 sp 3 P F F F 2p 2p 2p sp N 3 H2O i. & ii. Lewis structure & formal charge O H 0H 0 0 iii. number of bonding pair : 2 number of lone pair:2 iv. molecular geometry: bent H O H v. valence orbital diagram O (ground state): 2s 2p O (excited state): 2s 2p O (hybrid state): sp 3 H (ground state): 1s vi. orbital overlapping diagram sp 3 sp 3 sp 3 P H H 1s 1s sp O 3
SESSION 2023/2024 TOPIC 4: CHEMICAL BONDING CHEMISTRY SK015 80 PCl5 i. & ii. Lewis structure & formal charge Cl P Cl Cl Cl Cl 0 0 0 0 0 0 iii. number of bonding pair : 5 number of lone pair:0 iv. molecular geometry: trigonal bipyramidal Cl P Cl Cl Cl Cl v. valence orbital diagram P (ground state): 3s 3p 3d P (excited state): 3s 3p 3d P (hybrid): sp 3 d 3d Cl (ground state): 3s 3p vi. orbital overlapping diagram sp 3 d sp 3 d sp 3 d sp 3 d sp 3 d Cl P Cl Cl Cl Cl 3p 3p 3p 3p 3p SF4
SESSION 2023/2024 TOPIC 4: CHEMICAL BONDING CHEMISTRY SK015 81 i. & ii. Lewis structure & formal charge F S F F F 0 0 0 0 0 iii. number of bonding pair : 4 number of lone pair:1 iv. molecular geometry: see-saw F S F F F v. valence orbital diagram S (ground state): 3s 3p 3d S (excited state): 3s 3p 3d S (hybrid): sp 3 d 3d F (ground state): 2s 2p vi. orbital overlapping diagram sp 3 d sp 3 d sp 3 d sp 3 d sp 3 d S F F F F 2p 2p 2p 2p ICl3 i. & ii. Lewis structure & formal charge Cl I Cl Cl 0 0 0 0 iii. number of bonding pair : 3 number of lone pair:2
SESSION 2023/2024 TOPIC 4: CHEMICAL BONDING CHEMISTRY SK015 82 iv. molecular geometry: T-shape Cl I Cl Cl v. valence orbital diagram I (ground state): 5s 5p 5d I (excited state): 5s 5p 5d I (hybrid): sp 3 d 5d Cl (ground state): 3s 3p vi. orbital overlapping diagram sp 3 d sp 3 d sp 3 d sp 3 d sp 3 d Cl I Cl Cl 3p 3p 3p XeF2 i. & ii. Lewis structure & formal charge F Xe F 0 0 0 iii. number of bonding pair : 2 number of lone pair:3 iv. molecular geometry: linear F Xe F v. valence orbital diagram Xe (ground state): 5s 5p 5d Xe (excited state):
SESSION 2023/2024 TOPIC 4: CHEMICAL BONDING CHEMISTRY SK015 83 5s 5p 5d Xe (hybrid): sp 3 d 5d F (ground state): 2s 2p vi. orbital overlapping diagram sp 3 d sp 3 d sp 3 d sp 3 d sp 3 d F F 2p 2p Xe SF6 i. & ii. Lewis structure & formal charge F S F F F F F 0 0 0 0 0 0 iii. number of bonding pair : 6 number of lone pair: 0 iv. molecular geometry: octahedral F S F F F F F v. valence orbital diagram S (ground state): 3s 3p 3d S (excited state):
SESSION 2023/2024 TOPIC 4: CHEMICAL BONDING CHEMISTRY SK015 84 3s 3p 3d S (hybrid): sp 3 d 2 3d F (ground state): 2s 2p vi. orbital overlapping diagram sp 3 d 2 sp 3 d 2 sp 3 d 2 sp 3 d 2 sp 3 d 2 P F F F F F 2p 2p 2p 2p 2p sp 3 d 2 F 2p S BrF5 i. & ii. Lewis structure & formal charge F Br F F F 0 F 0 0 0 0 0 iii. number of bonding pair : 5 number of lone pair: 1 iv. molecular geometry: square pyramidal F Br F F F F v. valence orbital diagram Br (ground state): 5s 5p 5d
SESSION 2023/2024 TOPIC 4: CHEMICAL BONDING CHEMISTRY SK015 85 Br (excited state): 5s 5p 5d Br (hybrid): sp 3 d 2 5d F (ground state): 2s 2p vi. orbital overlapping diagram sp 3 d 2 sp 3 d 2 sp 3 d 2 sp 3 d 2 sp 3 d 2 P F F F F F 2p 2p 2p 2p 2p sp 3 d 2 Br XeF4 i. & ii. Lewis structure & formal charge F Xe F F 0 F 0 0 0 0 iii. number of bonding pair : 4 number of lone pair: 2 iv. molecular geometry: square planar F Xe F F F v. valence orbital diagram Xe (ground state): 5s 5p 5d Xe (excited state): 5s 5p 5d
SESSION 2023/2024 TOPIC 4: CHEMICAL BONDING CHEMISTRY SK015 86 Xe (hybrid): sp 3 d 2 5d F (ground state): 2s 2p vi. orbital overlapping diagram sp 3 d 2 sp 3 d 2 sp 3 d 2 sp 3 d 2 sp 3 d 2 P F F F F 2p 2p 2p 2p sp 3 d 2 Xe 7. a) -hydrogen bond -dipole-dipole forces -metallic bond - London dispersion forces b) i. CH3Br – van der Waals forces CH3F – van der Waals forces Boiling point of CH3Br > CH3F. • CH3Br bigger than CH3F. • Strength of van der Waals forces between molecules CH3Br > CH3F. • More energy needed to overcome forces between CH3Br molecules than CH3F molecules. ii. NH3 – hydrogen bond CH4 – van der Waals forces Boiling point of NH3 > CH4. • Hydrogen bond stronger than van der Waals forces. • More energy needed to break hydrogen bonds between NH3 molecules. iii. CCl4 – non- polar molecules - London dispersion forces CH3Cl – polar molecules - dipole-dipole forces Boiling point of CH3Cl > CCl4. • Dipole-dipole forces stronger than London dispersion forces. • More energy needed to overcome dipole-dipole forces between CH3Cl molecules. iv. H2O – hydrogen bond NH3 – hydrogen bond Boiling point of H2O > NH3. • O is more electronegative than N. • Strength of hydrogen bond between molecules H2O > NH3. • More energy needed to break hydrogen bonds between H2O molecules.
SESSION 2023/2024 TOPIC 4: CHEMICAL BONDING CHEMISTRY SK015 87 v. H2O – hydrogen bond HF – hydrogen bond Boiling point of H2O > HF. • H2O can form more hydrogen bond than HF. • Strength of hydrogen bond between molecules H2O > HF. • More energy needed to break hydrogen bonds between H2O molecules. c) i. Be Be2+ e e e e e e e e e e e e e e e e e e e e e e e e Be2+ Be2+ Be2+ Be2+ Be2+ Be2+ Be2+ Be2+ Be2+ Be2+ Be2+ • When Be atoms are arrange closely packed to each other, each of Be atom will released its valence electrons and forming sea of delocalized electrons and Be2+ ions. • The attractive forces between Be2+ ions and sea of electrons forming metallic bond. Mg Mg2+ e e e e e e e e e e e e e e e e e e e e e e e e Mg2+ Mg2+ Mg2+ Mg2+ Mg2+ Mg2+ Mg2+ Mg2+ Mg2+ Mg2+ Mg2+ • When Mg atoms are arrange closely packed to each other, each of Mg atom will released its valence electrons and forming sea of delocalized electrons and Mg2+ ions. • The attractive forces between Mg2+ ions and sea of electrons forming metallic bond. ii. - size of ion Mg2+ > Be 2+ iii. - melting point of Be > Mgl. - size of ion Mg2+ > Be2+ . - Be metal has stronger metallic bond.
SESSION 2023/2024 TOPIC 4: CHEMICAL BONDING CHEMISTRY SK015 88 KUMBE 4 1. a) possible structures and formal charge C O O H H 0 0 0 0 0 C O O H H -1 0 0 0 +1 A B most plausible structure. Structure A is the most plausible structure because the formal charge for each atom is zero. b) i. SF2 F S F 0 0 0 stable, formal charge of all atoms are zero. ii. SF3 + *correction F S + F F 0 0 0 unstable, formal charge of S is +1. iii. SF4 F S F F F 0 0 0 0 0 stable, formal charge of all atoms are zero. iv. SF5 + *correction F S + F F F F 0 0 0 0 0 unstable, formal charge of S is +1. v. SF6 F S F F F F F 0 0 0 0 0 0 0 stable, formal charge of all atoms are zero.
SESSION 2023/2024 TOPIC 4: CHEMICAL BONDING CHEMISTRY SK015 89 2. a) SiF4 F Si F F F • 4 electron pairs around central atom. • Electron pair arrangement: tetrahedral • 4 Bonding pair and no lone pair • Based on VSEPR theory, the valence electron pairs around central atom are oriented as far as possible to minimize the repulsion between them. • The strength of repulsion of Bonding Pair-Bonding Pair are equals. • Molecular geometry: tetrahedral SF4 F S F F F • 5 electron pairs around central atom. • Electron pair arrangement: trigonal bipyramidal • 4 Bonding pair and 1 lone pair • Based on VSEPR theory, the valence electron pairs around central atom are oriented as far as possible to minimize the repulsion between them. • The strength of repulsion are Lone Pair-Bonding Pair > Bonding Pair-Bonding Pair. • Molecular geometry: see-saw XeF4 F Xe F F F • 6 electron pairs around central atom. • Electron pair arrangement: octahedral • 4 Bonding pair and 2 lone pair • Based on VSEPR theory, the valence electron pairs around central atom are oriented as far as possible to minimize the repulsion between them. • The strength of repulsion are Lone pair-bonding > Lone Pair-Bonding Pair > Bonding Pair-Bonding Pair. • Molecular geometry: square planar. b) All species have 4 electron pairs around their central atom. Therefore, Electron pair arrangement for all species are tetrahedral NH2 - • 2 Bonding pair and 2 lone pair • Based on VSEPR theory, the valence electron pairs around central atom are oriented as far as possible to minimize the repulsion between them. • The strength of repulsion are Lone pair-bonding > Lone Pair-Bonding Pair > Bonding Pair-Bonding Pair. • Molecular geometry: bent • The H-N-H angle: 105o .
SESSION 2023/2024 TOPIC 4: CHEMICAL BONDING CHEMISTRY SK015 90 NH3 • 3 Bonding pair and 1 lone pair • Based on VSEPR theory, the valence electron pairs around central atom are oriented as far as possible to minimize the repulsion between them. • The strength of repulsion are Lone Pair-Bonding Pair > Bonding Pair-Bonding Pair. • Molecular geometry: trigonal pyramidal • The H-N-H angle: 107o . NH4 + • 4 Bonding pair and no lone pair • Based on VSEPR theory, the valence electron pairs around central atom are oriented as far as possible to minimize the repulsion between them. • The strength of repulsion of Bonding Pair-Bonding Pair are equals. • Molecular geometry: tetrahedral • The H-N-H angle: 109 o . 3. PF3 F P F F • Molecular geometry trigonal pyramidal. F P F F • F is more electronegative than P. P-F bond is polar. • Bond dipole cannot cancel each other. μ ≠ 0. • Polar. BF3 F B F F • Molecular geometry trigonal planar. F B F F • F is more electronegative than B. B-F bond is polar. • Bond dipole can cancel each other. μ = 0. • Non Polar. 4. a) type of hybrid H N C H C H H O O H sp3 sp3 sp3 sp2 sp2 a b a b
SESSION 2023/2024 TOPIC 4: CHEMICAL BONDING CHEMISTRY SK015 91 b) orbital overlapping diagram N (ground state): 2s 2p N (excited state): 2s 2p N (hybrid): sp 3 Ca (ground state): 2s 2p Ca (excited state): 2s 2p Ca (hybrid): sp 3 Cb (ground state): 2s 2p Cb (excited state): 2s 2p Cb (hybrid): sp 2 2p Oa (ground state): 2s 2p Oa (excited state): 2s 2p Oa (hybrid state): sp 2 2p Ob (ground state):
SESSION 2023/2024 TOPIC 4: CHEMICAL BONDING CHEMISTRY SK015 92 2s 2p Ob (excited state): 2s 2p Ob (hybrid state): sp 3 H (ground state): 1s sp 3 sp 3 sp 3 P H H 1s 1s sp 3 N sp 3 sp 3 H H 1s 1s sp 3 sp 3 Ca sp 2 sp 2 sp 2 Cb sp 2 sp 2 sp 2 Oa 2p 2p sp 3 sp 3 sp 3 sp 3 Ob H 1s 5. a) Boiling point of ethanol > dimethyl ether. • Ethanol can form Hydrogen Bond. • dimethyl ether can only form van der Waals forces. • Hydrogen Bond stronger than van der Waals forces. • More energy needed to break the hydrogen bond between ethanol. b) Boiling point of calcium is higher than that of potassium. • Ca has 2 Valence electrons, while K has 1 Valence electrons. • Strength of Metallic Bond between Ca atoms > between K atoms. • More energy needed to break the metallic bond between Ca atoms. c) ice floats on water. • In ice, water is tetrahedrally bonded to other four water molecules to form open hexagonal structure with many empty space between molecules. • Thus, ice occupies larger volume than liquid. • As a result, water is less dense than water. d) Copper can easily be shaped into pipes and drawn into wires. • In solid state, Cu atoms are arranged closely packed. • When sufficient force is applied to the metal, one layer of atoms can slide over another without disrupting the metallic bonding. • As a result, metals are malleable and can be drawn into wires (ductile).