FSS Chemistry- Miss.Sumathi

FSS 11034 Chemistry- Miss.Sumathi
Chemical Bonding : Chapter 3 11/23/2018 FSS Chemistry- Miss.Sumathi .

Valence electrons are the outer shell electrons of an atom. The valence electrons are the electrons that particpate in chemical bonding. Group # of valence e- e- configuration 1A 1 ns1 2A 2 ns2 3A 3 ns2np1 4A 4 ns2np2 5A 5 ns2np3 6A 6 ns2np4 7A 7 ns2np5 11/23/2018 FSS Chemistry- Miss.Sumathi 9.1

11/23/2018 FSS Chemistry- Miss.Sumathi 9.1

Ionic Bond 11/23/2018 FSS Chemistry- Miss.Sumathi

In the formation of electrovalent bond / ionic bond: An ionic bond formed by electrostatic forces. Ionic bond formed by ions with 2 different charges and through a electron transfer. 11/23/2018 FSS Chemistry- Miss.Sumathi

Metal elements will donate electrons while non-metal will receive electrons to achieve octet. This happen because metal more electropositive while non-metal more electronegative. 11/23/2018 FSS Chemistry- Miss.Sumathi

Example : Na Na e- 1s22s22p63s s22s22p6 (obey the octet rule) Cl + e- Cl- 1s22s22p63s23p5 1s22s22p63s23p6 11/23/2018 FSS Chemistry- Miss.Sumathi

VIDEO 1 Formation can be described by Lewis structure – valence e- represented as dot or cross. + - xx xx Na • Cl Na Cl x • x x x xx xx xx (formation of electrovalence bond ) 11/23/2018 FSS Chemistry- Miss.Sumathi

The Ionic Bond Li+ F - Li + F 1s22s1 1s22s22p5 1s2 1s22s22p6 Li Li+ + e- e- + F - F - Li+ + Li+ 11/23/2018 FSS Chemistry- Miss.Sumathi 9.2

Exercise: a) Calcium bromide, CaBr2 b) Plumbum oxide, PbO 11/23/2018 FSS Chemistry- Miss.Sumathi

Covalent Bond 11/23/2018 FSS Chemistry- Miss.Sumathi

Formation of Covalent Bond Formed by sharing 1 or more pairs of valence electrons between the bonded atoms, involving only-non metal atoms. . . .. H H H H or H ─ H 11/23/2018 FSS Chemistry- Miss.Sumathi

- Atoms other than H tends to form bonds until it is surrounded by 8 valence electrons. Lone pairs are pairs of valence electrons that is not involved in covalent bond formation. Can form different types of covalent bonds single bond, 2 atoms are held by 1 pair of e. double bond, 2 atoms shared 2 pairs of e. 11/23/2018 FSS Chemistry- Miss.Sumathi

(share 1 pair electrons)
Example: F2 xx xx xx xx xx F + F xx F x x F xx xx xx xx xx xx xx Covalent bond (share 1 pair electrons) Non metal Non metal Example: HCl .. .. H Cl H Cl . . .. .. .. .. x x 11/23/2018 FSS Chemistry- Miss.Sumathi

Single bond – two atoms share a pair of electrons 7e- 7e- 8e- 8e- F F + F Lewis structure of F2 lone pairs F single covalent bond single covalent bond F 11/23/2018 FSS Chemistry- Miss.Sumathi

Lewis structure of water single covalent bonds 2e- 8e- 2e- H + O + H O H or Double bond – two atoms share two pairs of electrons 8e- 8e- 8e- O C or O C double bonds double bonds Triple bond – two atoms share three pairs of electrons 8e- N 8e- or N triple bond triple bond 11/23/2018 FSS Chemistry- Miss.Sumathi 9.4

Formation of Dative Bond
Covalent bond formed when only 1 atom can provide both electrons of the shared pairs. - Also known as coordinate bond. 11/23/2018 FSS Chemistry- Miss.Sumathi

Example: Hydroxonium ion, H3O+ .. H :O: H O + Sometimes shown as arrow pointing from the donor atom to acceptor atom. 11/23/2018 FSS Chemistry- Miss.Sumathi

PHYSICAL PROPERTIES IONIC BOND COVALENT BOND High melting and boiling points A large amount of energy is required to break the bond, because the ions are held together by strong electrostatic forces of attraction. Low melting and boiling points The melting and boiling points of covalent compounds are generally low. This is because of the fact that the forces between the molecules are weak and thus are easily overcome at low temperatures. 11/23/2018 FSS Chemistry- Miss.Sumathi

Ionic Bond Covalent bond Electrical conductor In solution or in their molten states, ions become free to move and good conductors of electricity in these states. However, these do not conduct in their solid state because of strong electrostatic forces between the ions, that does not make them mobile. Non-conductors Since covalent compounds do not give ions in solution, these are poor conductors of electricity in the fused or dissolved state. 11/23/2018 FSS Chemistry- Miss.Sumathi

Ionic Bond Covalent bond Solubility Ionic compounds are generally soluble in water and other polar solvents having high dielectric constants. This is due to larger electrostatic interactions between polar solvents and ions. However ionic compounds are insoluble in non-polar solvents. Solubility Covalent compounds are generally insoluble or less soluble in water and in other polar solvents. They are however, soluble in non-polar solvents such as benzene, carbon tetrachloride etc. 11/23/2018 FSS Chemistry- Miss.Sumathi

Lewis Structure 11/23/2018 FSS Chemistry- Miss.Sumathi

Writing Lewis Structures
Draw skeletal structure of compound showing what atoms are bonded to each other. Put the least electronegative element in the center. Count total number of valence e-. Add 1 for each negative charge. Subtract 1 for each positive charge. Complete an octet for all terminal atoms except hydrogen If structure contains too many electrons, form double and triple bonds on central atom as needed. 11/23/2018 FSS Chemistry- Miss.Sumathi

Write the Lewis structure of nitrogen trifluoride (NF3).
Step 1 – N is less electronegative than F, put N in center Step 2 – Count valence electrons N - 5 (2s22p3) and F - 7 (2s22p5) 5 + (3 x 7) = 26 valence electrons Step 3 – Draw single bonds between N and F atoms and complete octets on N and F atoms. Step 4 - Check, are # of e- in structure equal to number of valence e- ? 3 single bonds (3x2) + 10 lone pairs (10x2) = 26 valence electrons F N 11/23/2018 FSS Chemistry- Miss.Sumathi 9.6

Species Step NF3 1 Total no. of valence electron: 1 N atom = 1 x 5 = 5 3 F atoms = 3 x 1 = 3 8 2 H is less electronegative than F. Skeletal structure: F N F F 3 Draw a single bond. Complete the octets of the terminal atoms. .. F ─ N ─ F  11/23/2018 FSS Chemistry- Miss.Sumathi

Write the Lewis structure of the carbonate ion (CO32-).
Step 1 – C is less electronegative than O, put C in center Step 2 – Count valence electrons C - 4 (2s22p2) and O - 6 (2s22p4) -2 charge – 2e- 4 + (3 x 6) + 2 = 24 valence electrons Step 3 – Draw single bonds between C and O atoms and complete octet on C and O atoms. Step 4 - Check, are # of e- in structure equal to number of valence e- ? 3 single bonds (3x2) + 10 lone pairs (10x2) = 26 valence electrons Step 5 - Too many electrons, form double bond and re-check # of e- 2 single bonds (2x2) = 4 1 double bond = 4 8 lone pairs (8x2) = 16 Total = 24 O C 11/23/2018 FSS Chemistry- Miss.Sumathi 9.6

Try it out What is the Lewis structure for SF4? What is the Lewis structure for CCl4 (a substance once used as a dry cleaning solvent until it was found to be very toxic) Draw Lewis structure that obey the octet rule for the ions NO3-, SO32- 11/23/2018 FSS Chemistry- Miss.Sumathi

Intermolecular Forces and Liquids and Solids
11/23/2018 FSS Chemistry- Miss.Sumathi Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Intermolecular forces are attractive forces between molecules. generally much weaker than covalent bonds. The strength of intermolecular forces determine the physical properties of the substances 11/23/2018 FSS Chemistry- Miss.Sumathi

Attractive forces between neutral molecules are 1. Van der Waals forces 2. Hydrogen Bond 11/23/2018 FSS Chemistry- Miss.Sumathi

Van der Waals forces 3 types of Van der Waals forces a. dipole-dipole forces b. induce dipole-dipole forces c. London dispersion forces The intermolecular forces increase in strength according to the following; London < dipole-dipole < H-bonding dispersion 11/23/2018 FSS Chemistry- Miss.Sumathi

(a) Dipole-Dipole Forces
VIDEO 1 A dipole-dipole forces exists between neutral polar molecules. 11/23/2018 FSS Chemistry- Miss.Sumathi

Orientation of Polar Molecules in a Solid
11/23/2018 FSS Chemistry- Miss.Sumathi

The strength of dipole-dipole forces depends on the dipole moment of the molecule. A more polar molecule, have stronger dipole-dipole forces. Example: the dipole-dipole forces in H-Cl are stronger than in H-Br 11/23/2018 FSS Chemistry- Miss.Sumathi

b) London Dispersion Forces
VIDEO 2 b) London Dispersion Forces Exist in all atoms and molecules. Non-polar molecules would not seem to have any basis for attractive interactions At any instant one side of the molecule has higher electron density while the other side has lower electron density. At this instant, the atoms or molecules become a small instantaneous dipole. Then, induce a dipole on the neighboring atom and molecule. 11/23/2018 FSS Chemistry- Miss.Sumathi

Polarizability is the ease with which the electron distribution in the atom or molecule can be distorted. Polarizability increases with: greater number of electrons more diffuse electron cloud Dispersion forces usually increase with molar mass. 11/23/2018 FSS Chemistry- Miss.Sumathi

Factors which influence van der Waals forces
Molecular size Molecular shape Molecular Polarity 11/23/2018 FSS Chemistry- Miss.Sumathi

the bigger molecules are "stickier".
i. Molecular Size VIDEO 3 go down a group, number of electrons increases, atomic radius increases. The more electrons, the more distance over which they can move, the bigger the possible temporary dipoles and therefore the bigger the dispersion forces. the bigger molecules are "stickier". 11/23/2018 FSS Chemistry- Miss.Sumathi

VIDEO 4 ii. Molecular shape Long thin molecules can develop bigger temporary dipoles due to electron movement than short fat ones containing the same numbers of electrons. Long thin molecules can also lie closer together - these attractions are at their most effective if the molecules are really close. 11/23/2018 FSS Chemistry- Miss.Sumathi

iii. Molecular Polarity
VIDEO 5 The boiling points of ethane CH3CH3, and fluoromethane, CH3F, are: 11/23/2018 FSS Chemistry- Miss.Sumathi

CH4 is nonpolar: dispersion forces.
What type(s) of intermolecular forces exist between each of the following molecules? HBr HBr is a polar molecule: dipole-dipole forces. There are also dispersion forces between HBr molecules. SO2 SO2 is a polar molecule: dipole-dipole forces. There are also dispersion forces between SO2 molecules. S O CH4 CH4 is nonpolar: dispersion forces. 11/23/2018 FSS Chemistry- Miss.Sumathi

Example: N-H, O-H, or F-H bond
VIDEO 1 c)Hydrogen bonding attraction force between the positively-charged H atom of a molecule and the negatively-charged electronegative atom of another molecule. Example: N-H, O-H, or F-H bond 11/23/2018 FSS Chemistry- Miss.Sumathi

δ+ δ– δ+ δ– δ+ δ– H – F H – F H – F hydrogen bonds 11/23/2018 FSS Chemistry- Miss.Sumathi

Effects of Hydrogen Bond on Physical Properties
i) the boiling points ii) the solubility of simple covalent molecules such as NH3, CH3OH in water iii) The density of water and ice 11/23/2018 FSS Chemistry- Miss.Sumathi

Effects of Hydrogen Bonding on boiling point
Figure: The boiling point of the hydrides of element in group 14 to 17. 11/23/2018 FSS Chemistry- Miss.Sumathi

From the figure: The boiling points of hydrides of group 14 elements (CH4,SiH4, GeH4 and SnH4) displays normal behavior. CH4 < SiH4 < GeH4 < SnH4 11/23/2018 FSS Chemistry- Miss.Sumathi

The type of intermolecular forces exist between the molecules are only Van der Waals Hydrogen bonds are not present. The boiling point increase regularly when the relative molecular mass increases. because the van der Waals forces increase as the molecular size increases. 11/23/2018 FSS Chemistry- Miss.Sumathi

2. For hydrides of group 15, 16 & 17elements (except NH3, H2O & HF) hydrogen bonds are not present. The increase in the boiling points for the hydrides of each periodic group is due to the increase in van der waals forces as the molecular size increases. 11/23/2018 FSS Chemistry- Miss.Sumathi

3. The strength of H-bond is proportional to the polarity of the bond. Thus, H-F > H2O > NH3 However, boiling point increases in such order H2O > HF > NH3 Even though fluorine is more electronegative than oxygen, H2O has higher boiling point than HF because there are 4 H-bonds per H2O molecule compared to only 2 per HF molecule. HF has higher boiling point than NH3 because of stronger H-bond of HF. 11/23/2018 FSS Chemistry- Miss.Sumathi

ii) Effects of H-Bonding on the solubility of simple covalent compounds Water is a good solvent for liquids and gases consisting of small polar molecules, that can form hydrogen bonds with water molecules. For example, ammonia is soluble in water because ammonia molecules can form hydrogen bonds with water molecules. 11/23/2018 FSS Chemistry- Miss.Sumathi

H─N─H------:O─ H ----- :N─H
.. H─N─H------:O─ H :N─H Hydrogen bonds 11/23/2018 FSS Chemistry- Miss.Sumathi

Most organic compounds are insoluble in water. Organic compounds that are soluble in water include: - amines, for example ethylamine C2H5NH2. - alcohols, for example ethanol, C2H5OH. - Carboxylic acid, such as ethanoic acid, CH3CH2OH. Amines are soluble in water because the -NH2 group in amines can form H-bonds with the water molecules. 11/23/2018 FSS Chemistry- Miss.Sumathi

CH3–N-H------:O-H-----:N-CH3
.. .. H Hydrogen bonds 11/23/2018 FSS Chemistry- Miss.Sumathi

Alcohol and carboxylic acids are soluble in water because the -OH groups in the compounds can form H-bonds with the water molecules. However, not all organic compounds that contain -NH2 group or –OH groups are soluble in water. As the relative molecular mass increases, the non-polar hydrocarbon portion becomes larger. 11/23/2018 FSS Chemistry- Miss.Sumathi

Since hydrocarbons are insoluble in water, the solubility decrease as the relative molecular mass of the organic compound increases 11/23/2018 FSS Chemistry- Miss.Sumathi

R-OH------:O-H .. hydrogen bond 11/23/2018 FSS Chemistry- Miss.Sumathi

Lengths of Covalent Bonds
Bond Type Bond Length (pm) C-C 154 CC 133 CC 120 C-N 143 CN 138 CN 116 Bond Lengths Triple bond < Double Bond < Single Bond 11/23/2018 FSS Chemistry- Miss.Sumathi 9.4

Electron Affinity - measurable, Cl is highest
Electronegativity is the ability of an atom to attract toward itself the electrons in a chemical bond. Electron Affinity - measurable, Cl is highest X (g) + e X-(g) Electronegativity - relative, F is highest 11/23/2018 FSS Chemistry- Miss.Sumathi 9.5

VIDEO 2 Polarised bond ? Bonds between the atoms that are polarised because of the difference in electronegativities of the atoms. 11/23/2018 FSS Chemistry- Miss.Sumathi

VIDEO 3 Polar molecule A dipole molecule in which the positive and negative pole can be distinguished (because of the separation of the charge). Example:  +  O = C = O polar or not? 11/23/2018 FSS Chemistry- Miss.Sumathi

Polar covalent bond or polar bond is a covalent bond with greater electron density around one of the two atoms H F electron rich region electron poor region e- poor e- rich F H d+ d- 11/23/2018 FSS Chemistry- Miss.Sumathi 9.5

Dipole moment (µ) A quantitative measure of the polarity of a
bond that can only be measured exp. A polar molecule has µ ≠ 0 Non-polar molecule has µ = 0 11/23/2018 FSS Chemistry- Miss.Sumathi

The direction of polarity of a polar bond can be symbolised by a vector quantity ( ). The crossed end of the arrow is the positive end and the arrow head is the negative end. H  Cl 11/23/2018 FSS Chemistry- Miss.Sumathi

VIDEO 4 Example:   H  Cl µ ≠ 0    O = C = O µ = 0 11/23/2018 FSS Chemistry- Miss.Sumathi

Determining polar and non-polar molecules Use the three-step approach outlined below : Use electronegativity values to predict bond dipoles. Use the VSEPR method to predict the molecular shape. From the molecular shape, determine whether bond dipoles cancel to give a non-polar molecule or combine to produce a (resultant dipole moment) for the molecule. 11/23/2018 FSS Chemistry- Miss.Sumathi

Molecules with different atoms & asymmetrically arranged are polar.
Example:   H  Cl 11/23/2018 FSS Chemistry- Miss.Sumathi

Molecules with different atoms, symmetrically
arranged but having µ = 0 are non-polar. Example: VIDEO 5 In CCl4, each bond is polar. The molecule as a whole, however, is non polar 11/23/2018 FSS Chemistry- Miss.Sumathi

The molecule is non polar
Example: In SF6, each bond is polar. The molecule is non polar 11/23/2018 FSS Chemistry- Miss.Sumathi

Ammonia ( effect of lone pairs )
Example:    0 11/23/2018 FSS Chemistry- Miss.Sumathi

Which of the following molecules have a dipole
moment? H2O, CO2, SO2, and CH4 O H S O dipole moment polar molecule dipole moment polar molecule C H C O no dipole moment nonpolar molecule no dipole moment nonpolar molecule 11/23/2018 FSS Chemistry- Miss.Sumathi

Predicting the polarity of molecules.
Evaluation 2 Predicting the polarity of molecules. State which of them are polar and which are non-polar. a) H2O b) NH3 c) CCl4 d) CHCl3 11/23/2018 FSS Chemistry- Miss.Sumathi

polar molecules: H2O, NH3, CHCl3 non-polar molecule: CCl4
Answer: polar molecules: H2O, NH3, CHCl3 non-polar molecule: CCl4 11/23/2018 FSS Chemistry- Miss.Sumathi

Classify the following bonds as ionic, polar covalent, or covalent: The bond in CsCl; the bond in H2S; and the NN bond in H2NNH2. Cs – 0.7 Cl – 3.0 3.0 – 0.7 = 2.3 Ionic H – 2.1 S – 2.5 2.5 – 2.1 = 0.4 Polar Covalent N – 3.0 N – 3.0 3.0 – 3.0 = 0 Covalent 11/23/2018 FSS Chemistry- Miss.Sumathi 9.5

Single bond < Double bond < Triple bond
The enthalpy change required to break a particular bond in one mole of gaseous molecules is the bond energy. Bond Energy H2 (g) H (g) + DH0 = kJ Cl2 (g) Cl (g) + DH0 = kJ HCl (g) H (g) + Cl (g) DH0 = kJ O2 (g) O (g) + DH0 = kJ O N2 (g) N (g) + DH0 = kJ N Bond Energies Single bond < Double bond < Triple bond 11/23/2018 FSS Chemistry- Miss.Sumathi 9.10

Average bond energy in polyatomic molecules
H2O (g) H (g) + OH (g) DH0 = 502 kJ OH (g) H (g) + O (g) DH0 = 427 kJ Average OH bond energy = 2 = 464 kJ 11/23/2018 FSS Chemistry- Miss.Sumathi 9.10

Bond Energies (BE) and Enthalpy changes in reactions
Imagine reaction proceeding by breaking all bonds in the reactants and then using the gaseous atoms to form all the bonds in the products. DH0 = total energy input – total energy released = SBE(reactants) – SBE(products) 11/23/2018 FSS Chemistry- Miss.Sumathi 9.10

Use bond energies to calculate the enthalpy change for:
H2 (g) + F2 (g) HF (g) DH0 = SBE(reactants) – SBE(products) Type of bonds broken Number of bonds broken Bond energy (kJ/mol) Energy change (kJ) H 1 436.4 F 1 156.9 Type of bonds formed Number of bonds formed Bond energy (kJ/mol) Energy change (kJ) H F 2 568.2 1136.4 DH0 = – 2 x = kJ 11/23/2018 FSS Chemistry- Miss.Sumathi 9.10

Comparison of Ionic and Covalent Compounds

Classification of bonds by difference in electronegativity
Bond Type Covalent  2 Ionic 0 < and <2 Polar Covalent Increasing difference in electronegativity Covalent share e- Polar Covalent partial transfer of e- Ionic transfer e- 11/23/2018 FSS Chemistry- Miss.Sumathi 9.5

Metallic Bond A metallic bond can be defined as the electrostatic force between the positively charged metallic ions and the ‘sea’ of electrons . 11/23/2018 FSS Chemistry- Miss.Sumathi

In a metallic bond, metals atoms can be imagined as an array of positive ions immersed in a sea of delocalized valence electrons. These delocalized electrons are not bound to individual atoms and they can therefore serve to bind large numbers of metal atoms together. 11/23/2018 FSS Chemistry- Miss.Sumathi

PHYSICAL PROPERTIES Metals are shiny solids are room temperature (except mercury), with characteristic high melting points and densities. Properties of metals: Able to be deformed without breaking. Malleability is the ability of a metal to be hammered into shapes. Ductility is the ability of a metal to be drawn into wire. Because the valence electrons can move freely (or mobility of the delocalized electrons), metals are good heat conductors and electrical conductors. 11/23/2018 FSS Chemistry- Miss.Sumathi

α The change of melting point and boiling points
A melting point of a metal indicates the strength of its metallic bonding in its structure. The strength of no. of valence e per atom metallic bonding radius of the atom α 11/23/2018 FSS Chemistry- Miss.Sumathi

So, the bonding will be weaker in sodium ( 1 valence e) compared to magnesium (2 valence e) and aluminium (3 valence e). 11/23/2018 FSS Chemistry- Miss.Sumathi

VIDEO 2 Table : The melting points and the boiling points for elements in group 1,2,13 and the block. Element Na Mg Al Li Be B Melting point (0C) 98 650 660 180 1280 2300 Boiling point (0C) 892 1107 2450 1330 2480 3930 No of valence electron 1 2 3 11/23/2018 FSS Chemistry- Miss.Sumathi

Molecular Geometry Def: The 3D arrangement of atoms in a molecule.
affects physical and chemical properties. predicted by using Valence-Shell Electron Pair Repulsion (VSEPR) model. 11/23/2018 FSS Chemistry- Miss.Sumathi

VIDEO 2 VSEPR The study of molecular geometry. States “The valence electron pairs surrounding a central atom repel one another. Thus, the orbital containing those electron pairs are oriented to be as far apart as possible”. 11/23/2018 FSS Chemistry- Miss.Sumathi

bonding-pair vs. bonding
3 types of repulsive forces: between bonding pairs between lone pairs between a bonding pair & lone pair bonding-pair vs. bonding pair repulsion lone-pair vs. bonding pair repulsion lone-pair vs. lone pair repulsion < < 11/23/2018 FSS Chemistry- Miss.Sumathi

VSEPR AB2 2 linear linear AB3 3 trigonal planar AB4 4 tetrahedral
Class # of atoms bonded to central atom # lone pairs on central atom Arrangement of electron pairs Molecular Geometry AB2 2 linear linear AB3 3 trigonal planar AB4 4 tetrahedral tetrahedral AB5 5 trigonal bipyramidal AB6 6 octahedral octahedral 11/23/2018 FSS Chemistry- Miss.Sumathi 10.1

2 atoms bonded to central atom 0 lone pairs on central atom
Cl Be 2 atoms bonded to central atom 0 lone pairs on central atom 11/23/2018 FSS Chemistry- Miss.Sumathi 10.1

> bonding-pair vs. bonding pair repulsion lone-pair vs. lone pair
lone-pair vs. bonding > 11/23/2018 FSS Chemistry- Miss.Sumathi

VSEPR trigonal planar trigonal planar AB3 3 trigonal planar AB2E 2 1
Class # of atoms bonded to central atom # lone pairs on central atom Arrangement of electron pairs Molecular Geometry trigonal planar trigonal planar AB3 3 trigonal planar AB2E 2 1 bent 11/23/2018 FSS Chemistry- Miss.Sumathi 10.1

VSEPR AB4 4 tetrahedral tetrahedral trigonal pyramidal AB3E 3 1
Class # of atoms bonded to central atom # lone pairs on central atom Arrangement of electron pairs Molecular Geometry AB4 4 tetrahedral tetrahedral trigonal pyramidal AB3E 3 1 tetrahedral 11/23/2018 FSS Chemistry- Miss.Sumathi 10.1

VSEPR AB4 4 tetrahedral tetrahedral AB3E 3 1 tetrahedral trigonal
Class # of atoms bonded to central atom # lone pairs on central atom Arrangement of electron pairs Molecular Geometry AB4 4 tetrahedral tetrahedral AB3E 3 1 tetrahedral trigonal pyramidal AB2E2 2 2 tetrahedral bent H O 11/23/2018 FSS Chemistry- Miss.Sumathi 10.1

VSEPR trigonal bipyramidal trigonal bipyramidal AB5 5 trigonal
Class # of atoms bonded to central atom # lone pairs on central atom Arrangement of electron pairs Molecular Geometry trigonal bipyramidal trigonal bipyramidal AB5 5 trigonal bipyramidal distorted tetrahedron AB4E 4 1 11/23/2018 FSS Chemistry- Miss.Sumathi 10.1

VSEPR trigonal bipyramidal trigonal bipyramidal AB5 5 AB4E 4 1
Class # of atoms bonded to central atom # lone pairs on central atom Arrangement of electron pairs Molecular Geometry trigonal bipyramidal trigonal bipyramidal AB5 5 AB4E 4 1 trigonal bipyramidal distorted tetrahedron trigonal bipyramidal AB3E2 3 2 T-shaped Cl F 11/23/2018 FSS Chemistry- Miss.Sumathi 10.1

VSEPR trigonal bipyramidal trigonal bipyramidal AB5 5 AB4E 4 1
Class # of atoms bonded to central atom # lone pairs on central atom Arrangement of electron pairs Molecular Geometry trigonal bipyramidal trigonal bipyramidal AB5 5 AB4E 4 1 trigonal bipyramidal distorted tetrahedron AB3E2 3 2 trigonal bipyramidal T-shaped trigonal bipyramidal AB2E3 2 3 linear I 11/23/2018 FSS Chemistry- Miss.Sumathi 10.1

VSEPR AB6 6 octahedral square pyramidal Br F AB5E 5 1 octahedral Class
# of atoms bonded to central atom # lone pairs on central atom Arrangement of electron pairs Molecular Geometry AB6 6 octahedral square pyramidal Br F AB5E 5 1 octahedral 11/23/2018 FSS Chemistry- Miss.Sumathi 10.1

VSEPR AB6 6 octahedral AB5E 5 1 octahedral square pyramidal
Class # of atoms bonded to central atom # lone pairs on central atom Arrangement of electron pairs Molecular Geometry AB6 6 octahedral AB5E 5 1 octahedral square pyramidal square planar Xe F AB4E2 4 2 octahedral 11/23/2018 FSS Chemistry- Miss.Sumathi 10.1

Predicting Molecular Geometry
Draw Lewis structure for molecule. Count number of lone pairs on the central atom and number of atoms bonded to the central atom. Use VSEPR to predict the geometry of the molecule. What are the molecular geometries of SO2 and SF4? S F S O AB4E AB2E distorted tetrahedron bent 11/23/2018 FSS Chemistry- Miss.Sumathi 10.1

Evaluation : Use the VSEPR model to predict the geometry of the following molecules and ions: C2H4 b) OF2 c) AlCl-4 d) AsH3 11/23/2018 FSS Chemistry- Miss.Sumathi

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