Thermochem & Quantum Mechanics Concepts

Enthalpy of Reaction

Energy change for a specific chemical equation based on its given stoichiometric coefficients

Enthalpy of Formation/Reaction Equation

ΔH°rxn = Σ (n ΔH°f(products)) - Σ (m ΔH°f(reactants))

Enthalpy of Formation / Heat of Formation

Energy change when 1 mole of a compound forms from its pure elements. Pressure is 1 bar, temperature is 289.15 K, concentration is 1M

Bond Dissociation Enthalpies

Only works when all components are gases. The amount of energy needed to break a specific chemical bond in a gaseous molecule by homolytic cleavage

Bond Dissociation Enthalpies Equation

ΔH = Σ(Bond Enthalpies of Reactants) - Σ(Bond Enthalpies of Products)

Wavelength (λ)

distance between two peaks or troughs in a wave

Frequency (ν)

number of waves (cycles) per second that pass a given point in space

Speed (c)

speed of light (3.00×108 m/s)

Blackbody Radiation

Ideal object which absorbs and emits all frequencies of radiation

Ultraviolet Catastrophe

Intensity with the classical approach diverges with increasing

Planck’s Constant

6.626x10^-34 J∙s

Energy of n Photons

∆Ephoton=nhν

Wavelength → Frequency Equation

c=λν

Frequency → Energy Equation

E = hv

Wavelength → Energy Equation

E=hc/λ​

Electron Kinetic Energy Equation

KE=hν−ϕ

Energy of an Electron Level Equation

En​=−2.18×10^-18(1/n²)

Energy Change During Transition Equation

ΔE=Ef​−Ei​

Number of Photons Equation

total energy/energy per photon

What does intensity control in the photoelectric effect?

The number of photons and the number of electrons emitted.

What does frequency control in the photoelectric effect?

• Whether electrons are emitted.

• The kinetic energy (KE) of emitted electrons.

Work function (ϕ)

The minimum energy required to remove an electron from a material.

What did classical physics predict about intensity?

Increasing intensity should increase electron KE. (which is wrong)

What did classical physics predict about low-frequency light?

Any frequency should work if the intensity is high enough. (which is wrong)

In the Bohr model, what does a higher n mean?

• Higher energy

• Farther from nucleus

What did de Broglie propose?

Matter can exhibit wave-like behavior. (which is true)

What does an orbital tell us?

The probability of finding an electron in a region of space.

Node

A region where the probability of finding an electron is zero.

Heisenberg Uncertainty Principle Equation

Δx * Δmu >= h / (4 π)

Schrodinger Equation

Ĥψ = Eψ

Wave Function

describes an atomic orbital, not an electron following a circular path around the nucleus

Principal Quantum Number (n)

defines the “shell” of orbitals

Angular Quantum Number (l)

determines the “subshell”, can have values of 0 to n-1

Magnetic Quantum Number (m_l)

orientation of the orbital, between -l to l

Electron Spin Quantum Number (m_s)

shows magnetic moment with two values, has values of ½ and -1/2

Pauli Exclusion Principle

no two electrons in an atom can have the same four quantum numbers (orbitals can only hold 2 electrons)

De Broglie Wavelength

λ = h / (mv)

Aufbau Principle

electrons are added to hydrgoen-like orbitals from the bottom up

Hund’s Rule

lowest energy configuration for an atom is the one having the maximum number of unpaired electrons allowed by the Pauli Exclusion Principle in a set of degenerate (same energy) orbitals

Periodic Trend: Moving across a row

increases nuclear charge

Periodic Trend: Moving down a column

increases electron shielding

Ionization energy & nuclear charge

increases from left to right

Electron Affinity

energy released as an atom accepts an electron
- electron affinities increase left to right across a row

Atomic size across a row

decrease in atomic radius

Atomic size down a column

increase in atomic radius

Isoelectric Series

ions with the same number of electrons

Electronegativity across a row

increased nuclear charge

Electronegativity down a column

increased shielding

decreased electronegativity

Lattice Energy

energy released when gaseous ions form an ionic solid