Bonding Justification+extra notes

Molecular geometry (overall)

1. Draw Lewis Structures 2. Compare/Contrast Lewis Structures and discuss geometry and bond angles of each 3. Restate statement

bond angles (overall)

1. draw Lewis structures 2. compare/contrast lewis structures and discuss geometry and bond angles of each 3. discuss lone pair creates electron-electron repulsion, which squeezes the bonds closer together 4. restate statement

expanded octet (overall)

1. draw Lewis structures 2. compare/contrast-->3rd energy down 3. discuss expanded octet-3rd energy lvl down can have expanded octet b/c d orbitals are available vs other-does not 4. restate statement

General format

1. draw lewis structure 2. compare/contrast 3. discuss 4. restate statement

Polarity (overall)

1. draw lewis structures 2. compare/contrast lewis structures and discuss geometry (bond angles) of each 3. discuss zero net dipole moment-->nonpolar vs net dipole moment in the direction of lone pair/atom-->polar 4. restate statement

resonance (overall)

1. draw lewis structures (if structure has resonance: draw ALL of them) 2. compare/contrast--> resonance 3. discuss resonance-movement of e- creates bond lengths that are equal and shorter than single but longer than double bonds vs other structure-does not 4. can also include bond order calculation- as BO increases, bond length decreases 5. restate statement

Resonance example: CO2 vs CO3^2-

According to the Lewis Structures above, both Co, and CO, contain a double bond, but CO, contains two double bonds and CO, contains one. Due to the fact that the double bond in CO can occur at different places, this structure exhibits resonance. The bond length for resonance structures are equal in length but are shorter than a single bond yet longer than a single bond. This is because the bond order of CO, is calculated to be 2 and bond order of CO, is 1.33. As bond order increases, bond length decreases. Therefore, the bond length of CO is longer than that of Co,.

Polarity example: AsF3 vs AsF5

According to the Lewis structures above, AsF, is trigonal pyramidal and AsF, is trigonal bipyramidal. Due to the molecular geometry and bond angles of each, the dipoles of AsF, cancel on another out, creating a zero net dipole moment. AsF, however, has a net dipole moment in the direction of the lone pair of electrons on As, resulting in a polar molecule. Therefore, AsF, is polar whereas AsF, is not

Molecular geometry example: IF3 vs NF3

According to the Lewis structures above, both IF, and NF, have three fluorines attached to the central atom, but IF, also has two lone pairs of electrons whereas NF, only has one lone pair. With five electron domains total including two lone pairs of electrons, IF, has the molecular geometry of T-shape with bond angles less than 90. NF, has a total of four electron domains including one lone pair of electrons which gives the structure a molecular geometry of trigonal pyramidal with bond angles of 109.5. Therefore, IF, and NF, have different molecular geometries with different bond angles.

Bond angle example: CH4 vs NH3

According to the lewis structures above, both central atoms in CH, and NH, have 4 electron domains which would exhibit a bond angle of 109.5°. Due to the lone pair of electrons attached to the N, the molecular geometry of NH, is trigonal pyramidal whereas the molecular geometry of CH, is tetrahedral because it does not have a lone pair of electrons attached to the central atom. In trigonal pyramidal structures, the bond angle is less than 109.5° because the lone pair of electrons creates electron/electron repulsion, squeezing the bond angles closer together. Therefore, the bond angles in NH, are smaler than the bond angles in CH

Explain: the atoms in a C2H4 molecule are located in a single plane, whereas those in a C2H6 molecule are not

Because of the double bond in C2H4, the molecular geometry around the carbons are trigonal planer which causes the atoms to be along the same plane, where as the geometry around each carbon in C2H6 is tetrahedral which is not on the same plane.

bond order equation

Bond order=#bond/#connections

Explain: The CH2F2 molecule is polar, whereas the CF4 molecule is not

Both CH2 F2 and CF for our tetrahedral. But C H2 F2 has 2C-H bonds and 2C-F bonds. Because of the bond angle of 109.5°, the dipole of C-H does not cancel out the dipoles of C-F therefore the molecule is polar. Because there are 4C-F bonds in CF4, the diaper all cancel out one another.

Expanded octet example: SF6 vs OF6

Both OF, and SF, would require 48 electrons total, creating 6 bonds attaching to the central atom. Since S, the central atom of SF, is in the third energy level, there are d orbitals available to hold extra electrons, making S have an expanded octet. O, however, does not have d orbitals available because it is located in the second energy level. Therefore, OF, cannot exist because O cannot expand its octet and cannot have 6 bonds attaching to the central atom.

Explain: the bonds of nitrate ion, NO2-, are shorter than the bonds in nitrate ion, and NO3-

Both an NO2 and NO3 have residence structures, but NO has two and NO3 has three. The bond order between NO2 is 1.5 and the bond order between NO3 is 1.33. As bond order increases bun length decreases, so NO2 has shorter bonds then NO3

____ are network covalent solids, which means they are held together by ____. This means that the structures are closely related to ___

Cgraphite, Cdiamond, SiO2 (sand) Covalent bonds Ionic crystal lattice structure

As the size (distance) of ions___ Fatt increases

Decreases

Explain: at ordinary conditions HF (normal boiling point equals 20°C)Is a liquid, where as HCl (normal boiling point = -114°C) is a gas

Even though F and CL are both bonded to H, the HF bond is drawn more tightly because F is more electronegative than CL. Because of this strong dipole-dipole attraction, HF is a liquid where is HL is a gas

Explain: HClO3 is a stronger acid than HCl

Even though HCLO3 and HCLO are both acids, HClO3 is a stronger acid because it has more O. Due to the energy of O, this causes an increase in E- density away from the OH bond leaving that bond weaker and easier to dissociate. Therefore HCLO3 is a stronger acid.

___ determines best Lewiston structure (want closes to ____)

Formal charge Zero

As the absolute value of charges ___ Fatt increases

Increase

As Fatt ___, the compound becomes more ionic and has ____ melting/boiling points

Increases Higher

Ionic compounds have ___ which is just ___

Lattice energy Fart (Coulomb's law)

Alloys are ___ Examples (2)

Mixture of metals Copper+Zinc=brass Copper+tin=bronze

Benzene(C6H6) has ___ which means ___

Resonance Equal bond lengths that are in between the length of a single and double bond

Explain: for sulfur, the fluorides SF2, SF4, and SF6 are known to exist, whereas for oxygen only OF2 is known to exist

S is in the third energy level, so it has D orbitals that it can use whereas O is in the second energy level and does not have D orbitals that it can use. Because of this, S can expand its octet in order to acquire more than eight electrons, but O cannot

bond energy equation

bonds broken (reactants)- bonds formed (products)

formal charge equation

formal charge= valence electrons - electrons (bonds only count as 1 e-