APCHEM 11th: Ionic and Covalent Bonds

Levels are …

Sublevels are …

Orbitals are …

Levels are the energy levels/periods/rows, Sublevels are s, p, d, and f, Orbitals are the positions that hold the electrons (# of orbitals half of # of maximum electrons)

Why do ionic bonds tend to have higher melting, boiling points than covalent bonds?

attraction of opposite charge is highly favorable, meaning more energy is needed to break this stability

What is the relationship between an ionic and covalent bond?

Ionic bonds are actually covalent bonds, it's just the electronegativity difference is so much that the electron is transferred completely and not shared

Describe all the covalent bond interactions involving electrons and nucleus

while there's attraction between all electrons and both nuclei, there is also repulsion between nuclei and between electrons, meaning covalent bonds form at the most ideal balance of these forces

What are the x and y axes of the covalent bond graph?

X: internuclear distance in picometers
Y: potential energy (Joules)

Explain the relationship between internuclear distance and potential energy

Up to the ideal/favorable point where the covalent bond fully forms, potential energy decreases due to the increasing nuclei-electron attraction, but afterwards, potential energy increases because the atoms are bonded together yet experience greater repulsion of like charges

How would a Cl-Cl bond compare to an H-H bond on the covalent bond graph?

Cl-Cl will have greater internuclear distance due to more shielding, and the shielding means the valence electrons are farther from both nuclei, so less attraction means greater potential energy

Name different levels of covalent bonds longest to shortest

single-double-triple

Bond energy definition

energy required to separate 1 mole of a certain bond

Lattice energy definition

the energy required to form one mole of a solid ionic compound from its gaseous ions

Coulomb's law

lattice energy = constant * (charge in Coulombs of ion #1)(charge in Coulombs of ion #2) over internuclear distance

Which factor has the bigger effect on lattice energy: internuclear distance or charge?

Charge

Describe the photoelectron spectroscopy graph

the y axis is number of e-, and the x axis is the binding energy that decreases as the electrons move further away from the nucleus

Starting from 1s, describe the gap widths seen on photoelectron spectroscopy graphs

As the energy levels and sublevels increase towards the right, the greatest gaps are between energy levels (EX: 1 to 2) and the smaller gaps are between sublevels (EX: s to p)

What does the Born Haber cycle show?

shows the enthalpy changes that occur in each step of separating/forming an ionic compound

Amount of main, possible steps in the Born Haber cycle and exceptions

5; however, some molecules don't require all steps to occur; EX: In MgS, both atoms are already single as opposed to Na + Cl2

Born Haber cycle step 1; +/- enthalpy change

convert any non-gaseous atoms into gaseous state; endothermic

Born Haber cycle step 2; enthalpy change

separate any diatomic atoms into single atoms; endothermic

Born Haber cycle step 3; enthalpy change

ionization energy is needed to remove the electron(s) from the cation; endothermic

Born Haber cycle step 4; enthalpy change

the anion's electron affinity energy attracts the cation's electron(s); exothermic

Born Haber cycle step 5; enthalpy change

the oppositely-charged gaseous ions now combine to form the final solid compound; exothermic

What do you have to note about electron affinity and ionization energies for atoms that can give away/accept 2 or more electrons?

if atoms give away multiple electrons, those electrons have different ionization energies; so atoms that accept multiple electrons have different electron affinity energies specific to each

If you still have leftover electrons, which atoms should most likely get those extra electrons? (3)

-more electronegative atoms

-atoms that currently have a positive formal charge

-atom that is most furthest down a period starting at period 3

Formal charge equation

of expected valence electrons - actual valence electrons

Polarity definition

the uneven sharing of electrons in molecules due to asymmetrical structure and different electronegativities

Resonance structure definition

structures in which the overall compound charge and position of the atoms stays the same, but the position of some electrons can move around due to not being localized

Hybrid structure 2 aspects

-more stable than the different resonance structures separate

-like a mix of all the resonance structures, so its bond length is between that of single and double bonds

Why can atoms period 3 and beyond expand their octets?

because they have an s, p and d sublevels, not just s and p

Valence Shell Electron Pair Repulsion theory

molecular geometries can be determined thanks to the repulsions between electrons and the greatest minimizations of those repulsions

5 electron domains

linear, trigonal planar, tetrahedral, trigonal bipyramidal, octahedral

Linear geometry angle measure

180˚

Trigonal planar angle measure

120˚

Tetrahedral angle measure and why?

109.5˚; to minimize repulsions, tetrahedral adopts a multi-plane structure which causes wider angles than what would've been in a planar structure

Trigonal bipyramidal angle measureS

-120˚ between the equatorial

-90˚ between the axial and equatorial

Octahedral angle measure

90˚

What is important to note about lone pairs when figuring out why molecular geometries are the certain shape they are?

lone pairs take up more space and thus have a wider range of repulsion, pushing the other electron pairs closer together

Trigonal planar: 2 molecular geometries and requirements for them

-trigonal planar: all electron pairs are bonded

-bent: 1 nonbonded electron pair

Tetrahedral: 3 molecular geometries and requirements for them

-tetrahedral: all bonded

-trigonal planar: 1 unbonded

-bent: 2 unbonded

If trigonal bipyramidal or octahedral happen to have unbonded electron pairs, where do they go?

the equatorial positions

Trigonal bipyramidal 4 molecular geometries and requirements

-trigonal bipyramidal: all bonded

-seesaw: 1 unbonded

-t-shaped: 2 unbonded

-linear: 3 unbonded

Octahedral: 3 molecular geometries and requirements

-octahedral: all bonded

-square pyramidal: 1 unbonded

-square planar: 2 unbonded

What 6 molecular geometries are symmetrical if all attached atoms are the same in each field?

-linear
-trigonal planar
-square planar
-trigonal bipyramidal
-octahedral
-tetrahedral

Symmetry in regards to trigonal bipyramidal and octahedral structures?

as long as the atoms in the equatorial positions are the same and the atoms in the axial positions are the same, then nonpolar

How to tell if a linear molecular is polar or not?

if atoms on both side of central atom are the same, then nonpolar because of equal dipoles

Polarity arrow trick note #1 for molecule geometries not linear

perform this for every plane of the molecule

Polarity trick #2 for molecular geometries not linear

for each bond, draw the dipole arrow in the appropriate direction

Polarity trick #3 for molecular geometries not linear

assemble the arrows into a cycle; if the cycle can repeat endlessly, it is nonpolar

Hybridization

when an atom is bonding, the s and p orbitals mix together to form hybridized orbitals which correlate with an electron geometry

When does hybridization of an atom not occur?

if atom does not have p orbitals; Ex: H

Along which 3 axes can the 3 p orbitals exist? Their directions?

x and z: horizontal and perpendicular of each other
y: vertical

what is the degrees measure between each of the 3 axes?

90˚

s orbital shape

sphere

p orbital shape

pair of lobes (like an 8)

What are hybrid/degenerate orbitals?

the different variations of the mixing of s and p orbitals (of equal energies) which all merge into one final hybridized structure

sp3 hybridization uses _ out of _ p orbitals and makes _ degenerate orbitals

3; 3; 4

sp3 electron geometry

tetrahedral

How many electrons can each hybridized orbital hold up to?

2

how does sp3 apply to molecules that may have the electron geometry tetrahedral, but molecular geometries of something else?

some hybridized orbitals will not be bonded and will just be holding unbonded electrons

What is joined during sp2 hybridization?

1s + any 2 of the 3 p orbitals (doesn't matter which 2 axes you choose)

sp2 makes _ degenerate orbitals and its electron geometry is

3; trigonal planar

what is a sigma bond?

a type of covalent bond in which the orbitals of different atoms overlap

does the pi bond form between 2 hybridized or non-hybridized p orbitals?

non-hybridized

how do pi bonds form?

pi bonds form perpendicular to sigma bonds and if the non-hybridized p-orbitals are aligned in the same direction

a single bond formed from 2 overlapping hybridized orbitals is a _

sigma bond

generally, a double bond consists of ____

a sigma and pi bond

generally, a triple bonds consists of _

a sigma bond and 2 pi bonds

how many p orbitals does sp hybridization use?

1 out of 3

sp hybridization forms _ degenerate bonds and its electron geometry is

2; linear