CHM 115 Exam 3 Review

Ionic Bonding

Type of bonding between a metal and a nonmetal. Involves an electron transfer and both achieve a noble gas configuration (ex. LiF)

electrostatic

Ions that transfer electrons have _ attractions with one another, forming an ionic solid.

Covalent Bonding

Type of bonding between a nonmetal and a nonmetal. Involves shared electrons being localized in a bond between the atoms

Metallic Bonding

Type of bonding between a metal and a metal. Creates a "sea" of delocalized electrons

Lattice Energy

Enthalpy change that accompanies one mole of an ionic solid separating into its component gaseous ions (opposite of formation energy)

Born-Haber Cycle

The series of steps from individual elements to ionic solid where all enthalpy changes are known except for the lattice energy. We can use Hess's law to find the unknown lattice energy

Sublimation

Li (s) --> Li (g) This first step of the Born-Haber cycle is known as…

Bonding Energy (1/2)

1/2F2 (g) --> F (g) This second step of the Born-Haber cycle is known as…

Ionization Energy

Li (g) --> Li+ (g) + e- This third step of the Born-Haber cycle is known as…

Electron Affinity

F (g) + e- --> F- (g) This fourth step of the Born-Haber cycle is known as…

Heat of Formation

Li (g) + 1/2F2 (g) --> LiF (s) This net total reaction of the Born-Haber cycle is known as…

increases

According to Coulomb's Law, as ionic charge increases, lattice energy _.

decreases

According to Coulomb's Law, as ionic radius increases, lattice energy ____.

MgF2, CsBr, KCl, CaS

Rank the lattice energies of these ionic solids from least to greatest: CsBr, KCl, CaS, and MgF2

Liquid (ions are free to move and carry currents)

In which phase of matter do ionic compounds best conduct electricity?

lattice

Ionic compounds tend to be hard, rigid, and brittle because of their ____ structure.

released, absorbed (this is really confusing especially if you've taken bio, but just know that this is the correct answer 😭)

Energy is when a bond forms, and energy is when a bond is broken. (released or absorbed)

The atoms are far apart; neither one of them is influenced by the other.

In this covalent bond formation graph, what does Point 1 represent?

The atoms begin getting closer, which increases the attractions between the atoms but also the repulsions between the electrons

In this covalent bond formation graph, what does Point 2 represent?

Maximum attraction between the atoms is achieved despite repulsion, and the system is at minimum energy

In this covalent bond formation graph, what does Point 3 represent?

The atoms are too close and because of high repulsion, the atoms would begin to distance themselves from each other

In this covalent bond formation graph, what does Point 4 represent?

attracting, repelling

A covalent bond arises from the balance between the nuclei ____ the electrons and the electrons and nuclei _____ each other.

Shared/Bonding Pair

Term for two shared electrons between two atoms

Lone/Unshared Pair

Term for an outer-level electron pair that is not involved in bonding

Bond Order

Term for the number of electron pairs being shared by a given pair of atoms

Bond Length

Term for the distance between the nuclei of bonded atoms

Bond Energy

Term for the energy needed to overcome the attraction between the nuclei and the shared electrons within a covalent bond

increases, decreases

As the bond order increases, the bond energy ____ and the bond length _____.

increases, decreases; decreases, increases

Within a group, bond length ____ while bond strength _____. Across a period, bond length _____ while bond strength _____.

energies

The different bond _ account for the heat released or absorbed in a reaction.

difference

The _ between the heat absorbed to break reactant bonds and the heat released to form reactant bonds can be used to calculate the enthalpy change of a reaction.

Electronegativity

Term for the relative ability of a bonded atom to attract shared electrons. Note that it cannot be directly measured, is a relative value, and has several different scales

inversely

As a general rule of thumb, electronegativity is _ related to atomic size.

polar (AKA have a partial charge separation, polarization, or bond dipole)

When bonded atoms have different electronegativity values, they are said to be _.

More electronegative atom

When drawing a polar arrow, should the arrowhead point towards the more or less electronegative atom?

nonpolar

When bonded atoms have the same electronegativity values, they are said to be _ and have no partial charge separation. Typical among diatomic molecules

ionic, covalent

A greater electronegativity difference causes a higher partial ____ character, and a smaller electronegativity difference causes a higher partial _____ character.

Lewis Dot Structure

Diagram of a molecule using atomic symbols, straight lines, and dots to depict the molecule's bonding

A straight line (between the bonded atoms)

How are bonding pairs represented in a Lewis structure?

Two dots (on the nonbonding side of the atom)

How are lone pairs represented in a Lewis structure?

The atom with the lowest electronegativity (except when told otherwise bc chem is dumb)

When drawing a Lewis dot structure, which atom should go in the center?

one, four, three, two, one

Some rules of thumb for Lewis structures:

H atoms form only ___ bond and can only ever be surrounding atoms.

C atoms form ____ bonds.

N atoms form ____ bonds.

O atoms USUALLY form ____ bonds.

F, Cl, Br, and I atoms form ___ bond.

Resonance Structures

Different Lewis structures that represent the same molecule. They have the same placement of atoms but have different locations for bonding and lone pairs. Not real bonding depictions

False. The actual structure is an average of the resonance structures. Its electrons are delocalized

True or False: For a molecule with multiple resonance structures, the actual molecular structure flips back and forth between all of the resonance structures.

locations/placements

To calculate the bond order of a resonance structure, divide the total number of bonds by the number of bond _.

Formal Charge

Term for the charge an atom would have if all electrons within a Lewis structure were shared equally

valence electrons

valence electrons

bonds (technically this term is "1/2 of shared valence electrons" but this term does the job and tbh idc so…)

The equation for formal charge is:

of - (# of unshared + # of )

smaller; adjacent; electronegative

Some tips for choosing the most important resonance structure:

Formal charges _ in magnitude are preferable.

Avoid like charges on _ atoms.

A more negative formal charge should lie on the more _ atom.

Octet Rule

States that atoms lose, gain, or share electrons so they can have a total of eight valence electrons (except this rule has a thousand exceptions but its whatever)

Beryllium (Be), Boron (B); odd; 3

Exceptions to the Octet Rule:

Elements and are commonly electron deficient.

A few molecules, called free radicals, have an ___ number of electrons.

Nonmetals from Period ____ or higher can have more than 8 electrons because of their available d orbitals.

VSEPR (Valence-Shell Electron-Pair Repulsion) Theory

States that valence electron groups around a central atom distance themselves to minimize repulsions between each other resulting in distinct molecular shapes

All of the above! (picture's unrelated, im just bored)

Which of the following count as 1 electron group?

Single Bond

Double Bond

Triple Bond

Lone Pair

Single Electron

central

Only valence electron groups around the _ atom determine molecular shape.

Electron Group Arrangement/Electron Geometry

Defined by both the bonding and nonbonding electron groups. It will be the same as the molecular shape if all of the electron groups are bonding

Molecular Shape/Geometry

Refers to the 3D arrangement that ONLY bonding electron groups create around the central atom

Bond Angle

Angle formed by the nuclei of two surrounding atoms with the nucleus of the central atom

All of the above! (again)

Which of the following characteristics of a molecule can be determined by a Lewis structure?

Elements Present

Number of Bonds

Types of Bonds

Number of Valence Electrons

Formal Charges

Molecular Shape

Bond Angles

Molecular Polarity

E -- nonbonding valence electron group (lone pair/electron)

n -- Number of nonbonding valence electron groups (functions as a subscript)

In the specific designation for molecular shapes, AXmEn, what do the E and n stand for?

Linear

Electron group arrangement of 2 electron groups (AX2). Forms an ideal bond angle of 180 degrees (Ex. CO2, BeCl2)

Trigonal Planar

Electron group arrangement of 3 electron groups (AX3). Forms ideal bond angles of 120 degrees (Ex. NO3-, SO3)

Tetrahedral

Electron group arrangement of 4 electron groups (AX4). Forms ideal bond angles of 109.5 degrees (Ex. CH4, SiCl4, ClO4-)

Trigonal Bipyramidal

Electron group arrangement of 5 electron groups (AX5). Forms ideal bond angles of 120 degrees (equatorial) and 90 degrees (axial) (Ex. PCl5, SOF4)

Octahedral

Electron group arrangement of 6 electron groups (AX6). Forms ideal bond angles of 90 degrees (Ex. SF6, IOF5)

equal

If all of the electron groups around a central atom are bonding groups, then the electron group geometry will ____ the molecular geometry.

Bent

Molecular shape resulting from 2 bonding groups and 1 lone pair (AX2E). Forms bond angles of <120 degrees (Ex. SO2, O3)

Trigonal Pyramidal

Molecular shape resulting from 3 bonding groups and 1 lone pair (AX3E). Forms bond angles of <109.5 degrees (Ex. NH3, PF3)

Bent

Molecular shape resulting from 2 bonding groups and 2 lone pairs (AX2E2). Forms bond angles of <109.5 degrees (Ex. H2O, OF2)

Seesaw

Molecular shape resulting from 4 bonding groups and 1 lone pair (AX4E). Forms bond angles of <120 degrees (equatorial) and <90 degrees (axial) (Ex. SF4, IF4)

T-shaped

Molecular shape resulting from 3 bonding groups and 2 lone pairs (AX3E2). Forms bond angles of <120 degrees (equatorial) and <90 degrees (axial) (Ex. ClF3, BrF3)

Linear

Molecular shape resulting from 2 bonding groups and 3 lone pairs (AX2E3). Forms bond angles of <120 degrees (equatorial) and 180 degrees (axial) (Ex. XeF2, I3)

Square Pyramidal

Molecular shape resulting from 5 bonding groups and 1 lone pair (AX5E). Forms bond angles of <90 degrees (Ex. BrF5, XeOF4)

Square Planar

Molecular shape resulting from 4 bonding groups and 2 lone pairs (AX4E2). Forms bond angles of 90 degrees (Ex. XeF4, ICl4)