CHEM121 - EXAM 3 REVIEW

speed of light ( c )

2.998 × 10⁸ m/s

photons

discrete amounts of energy absorbed or emitted by atoms

quanta

• used by Planck to explain the radiation emitted by incandescent objects

• used by Einstein to explain the photoelectric effect

work function (Φ)

the radiant energy required to dislodge a photoelectron from a metal surface

electron transitions between energy levels in an atom produce…

atomic emission spectra and atomic absorption spectra consisting of narrow lines at wavelengths corresponding to the change in energy of the electrons

matter waves

• proposed by De Broglie

• all moving particles have wave properties

Heisenberg uncertainty principle

both the position and momentum of an electron cannot be precisely known at the same time

Schrödinger wave equation

• mathematical expressions called wave functions (𝛙)

• 𝛙² defines the regions within an atom, called orbitals

orbitals

• describe the probability of finding an electron at a given distance from the nucleus

• have characteristic three-dimensional sizes, shapes, and orientations that are depicted by boundary-surface representations

principal quantum number n

defines orbital size and energy level

angular momentum quantum number l

defines orbital shape

magnetic quantum number m_l

defines orbital orientation in space

spin quantum number m_s

allows two opposite-spin electrons to share an orbital

Pauli exclusion principle

states that no two electrons in an atom can have the same four values of n, l, m_l, and m_s

aufbau principle

electrons fill the lowest-energy atomic orbitals of a ground-state atom first

electron configuration

set of numbers and letters expressing the number of electrons that occupy each orbital in an atom

electron configuration order

degenerate

having the same energy

Hund’s rule

states that in any set of degenerate orbitals, one electron must occupy each orbital before a second electron occupies any orbital in the set

effective nuclear charge (Z_eff)

the net nuclear charge experienced by outer-shell electrons when they are shieled by inner-shell electrons

atomic radius / sizes of atoms

• the size of atoms increase down a group of elements because valence-shell electrons with higher n values are farther from the nucleus

• the size of atoms decrease across a row of elements because the valence electrons experience higher effective nuclear charges.

ionization energy (IE)

the energy needed to remove one mole of electrons from one mole of atoms or ions in the gas phase

• increases with increasing effective nuclear charge across a row and decrease down a group

photoelectron spectra

• plots the relative number of electrons in an element and their binding energies

• can be used to identify metals and determine their electron configurations

electron affinity (EA)

the energy change that occurs when one mole of electrons combines with one mole of atoms or ions in the gas phase

calculating frequency from wavelength

ν = c/λ

calculating the energy of a photon

E = hc/λ

Planck’s constant (h)

6.626 × 10^-34 J

electrostatic potential energy (E_el)

• a measure of the strength of the attractions between cations and anions in an ionic compound

• directly proportional to the product of the ion charges and inversely proportional to the distance between the nuclei of the ions

polar covalent bonds

unequal electron sharing between atoms of different elements

electronegativity generally increases with…

increasing ionization energy

isoelectronic

having the same total number of electrons

metallic bond

delocalization of electrons

covalent bond

sharing of electrons

ionic bond

transfer of electrons