Bonding, IMF, Thermodynamics

Question 1

Lewis Dot Structure

Answer 1

Each dot represents a valence electron, single bonds (two electrons) are shared between two atoms in the bond, double bonds (four electrons), triple bonds (six electrons)

Question 2

Formal Charges

Answer 2

Tell us whether or not the atoms are sharing their electrons in the best way possible (not representative of actual charge of the element)

Formal Charge = Valence - (1/2 of Bonded Electrons) - # lone paired (nonbonded electrons)

Question 3

Resonance Structures

Answer 3

Accurate depiction of a molecule’s bonding that cannot be one in one single structure (often needed when there are double/triple bonds or formal charges and lone pairs)

Question 4

Resonance Hybrid

Answer 4

Depiction of resonance structures (ex. dotted line drawing of SO2)

Question 5

Major vs. Minor Resonance

Answer 5

Major resonance forms are those structurally favorable (all atoms have octet and no formal charges)

Question 6

Bond Dissociation Energy

Answer 6

Energy required to break a bond homolytically

Question 7

Homolytic Bond Cleavage

Answer 7

One electron of the bond being broken goes to each fragment of the molecule (formation of radicals)

Question 8

Heterolytic Bond Cleavage

Answer 8

AKA Dissociation, both electrons of the electron pair end up on the same atom (forming cation and anion)

Question 9

Bond length

Answer 9

The distance between two nuclei that are bonded to one another

Greater the s character, shorter the bond, stronger the bond

Question 10

Similar Bonds

Answer 10

Varying of atomic radii makes it hard to compare bond lengths/BDE of unlike bonds

Question 11

Bond Order

Answer 11

Directly related to bond length

Question 12

Covalent Bonds

Answer 12

Can be nonpolar or polar, with dipole moment

Nonpolar - electron density between two nuclei density is even

Polar - electron density is uneven bc electronegativity attracts electrons and creates a more partially negative side on one side of the molecule

Question 13

Coordinate Covalent Bond

Answer 13

One atom donates both of the shared electrons in a bond

Question 14

Ionic Bond

Answer 14

The gaining/losing of electrons that results in a cation/anion held together by electrostatic attraction

Question 15

Valence Shell Electron Pair Repulsion (VSEPR) Theory

Answer 15

Prediction of shapes of different molecules

Guided by the fact that since electrons repel one another, electron pairs (whether bonding or non bonding) attempt to move as far as possible from one another

Question 16

Hybridization

Answer 16

Method to rationalize observed chemical/structural trends. Character is based on how many things are attached to the atom in question (p number = number of things its attached to minus 1) *inclusive of lone pairs

sp - connected to two things
sp2 - 3 things
sp3 - 4 things

Question 17

Sigma bonds

Answer 17

2 electrons localized between two nuclei - formed by end-to-end overlap

Question 18

Pi bonds

Answer 18

2 electrons localized to region that lies on opposite sides of the plane (due to already existing sigma bond) side-to-side overlap

Therefore less stable than sigma bonds

Question 19

Molecular Polarity

Answer 19

Polarity can apply to a bond as a whole -> if a molecule contains no polar bonds, cannot be polar. If a molecule has 2+ polar bonds that have even electron density, makes them polar

Question 20

IMF

Answer 20

Weak interactions that take place between neutral molecules (NOT BONDS)

Question 21

Ion-dipole forces

Answer 21

Polar molecules attracted to ions

Question 22

Dipole-Dipole Forces

Answer 22

Attractions between positive end of one polar molecule and negative end of another molecule

Ex. Hydrogen bonding (strongest dipole-dipole force)

Question 23

Dipole-induced Dipole Force

Answer 23

Permanent dipole in one molecule may induce dipole in another neighboring nonpolar molecule (momentary)

Question 24

London Dispersion (instantaneous Dipole-induced-dipole)

Answer 24

Very weak transient interactions between instantaneous dipoles in nonpolar molecules.

Strength of dispersion forces increase as a result of size/molecular weight of molecule increasing

Question 25

Van Der Waals

Answer 25

Dipole/H bonding/London collective name, sometimes referring to only London Dispersion

Question 26

Hydrogen Bonding (NOF)

Answer 26

1) must have a covalent bond between H and either NOF
2) must have another molecule with a lone pair on either NOF atom

Ex. Water

More hydrogen bonding increases boiling point

Question 27

Vapor Pressure

Answer 27

Pressure exerted by gaseous phase of a liquid that evaporated from exposed surface of the liquid

Weaker a substance’s IMF, higher the vapor pressure, more easily it is to evaporate

Also temperature dependent (increases in kinetic energy increase vapor pressure)

Question 28

Volatile

Answer 28

Liquids (with high vapor pressure) that are easily vaporized

Question 29

Ionic Solids

Answer 29

Held together by electrostatic attraction between cations and anions in a lattice structure. This lattice structure held together by ionic bonds as well.

Most ionic substances are solid at room temperature, with bonds being strong

Bond strength increases as atomic radii/space between the two elements decrease; varying electronegativities (greater charge differences, stronger attraction)

Question 30

Network Solids

Answer 30

Connected lattice of covalent bonds. Network of intermolecular forces are same as intramolecular forces (covalent bonding) which makes them very strong. Hard solids at room temperature

Diamonds, quartz are examples

Question 31

Metallic Solids

Answer 31

Covalently bound lattice of nuclei and their inner shell electrons surrounded by sea/cloud of electrons

At least one valence electron (the conduction electrons) per atom not bound to anything in particular and freely moving

Creates excellent conductivity of heat and electricity (malleable)

All metals (except Hg solid at room temp)

Question 32

Molecular Solids

Answer 32

Held together by three Intermolecular interactions (H-bonding, Dipole-dipole, and London)

Significantly weaker than ionic, network or metallic bonds. Much lower melting/boiling points

Liquids/gas at room temperature

Question 33

Dipole Moment

Answer 33

Two atoms involved in the bond differ in electronegativity