Exam 3 (Chem)

Electron Spin

Built-in angular momentum of electrons, leading to quantization of their magnetic moment into distinct orientations. ranges from ½ to - ½

Stern-Gerlach Experiment

An experiment that revealed quantization of electron spin magnetic moment into only specific orientations.

Quantum Numbers

Set of four numbers (principal, angular momentum, magnetic, and spin quantum numbers) that define the properties of electrons in atoms.

Pauli Exclusion Principle

No two electrons in the same atom can have the same set of four quantum numbers.

Radial Distribution Function

A function that gives the probability of finding an electron at a certain distance from the nucleus. As n increases (energy) the probability becomes more expanded

Effective Nuclear Charge

The net positive charge experienced by an electron in a multi-electron atom, which reduces the full nuclear charge experienced by the electrons.

Hund's Rule

When electrons are placed into orbitals of equal energy, one electron enters each orbital until all orbitals are filled with one electron before any orbital gets a second.

Ionization Energy

The minimum energy required to remove an electron from an atom in its gas phase.

Electron Affinity

The energy change that occurs when an electron is added to a neutral atom in the gas phase.

Excited State

A state in which one or more electrons in an atom occupy higher energy orbitals compared to the ground state.

De brogile’s wavelength

A concept in quantum mechanics that relates the wavelength of a particle to its momentum, described by the equation \lambda=\frac{h}{p} , where h is Planck's constant and p is the momentum. *Does not apply to light

De brogile’s orbits

A stable orbit must be 2\pi r=n\lambda

For what kinds of particles and situations can the de Broglie relation be tested?

moving particles that are often microscopic like electrons by observing its wavelength properties

Uncertainty Principle

Therefore, the more narrowly the position is

measured, the more uncertainty there is in the

particle’s momentum (velocity), and vice versa.

If the position were known exactly, the momentum

would be completely unknown.

\Delta x\Delta px>=\frac{h}{4\pi}

Uncertainty Principle equation

\Delta x\Delta px>=\frac{h}{4\pi}

Schrodinger Equation

ψ2 , the square of the wave function, gives the probability of finding the particle in a certain region of space

Schrodinger Equation agreement

For the H atom, the energy levels predicted by the Schrödinger equation agree with the Rydberg formula (based on measurements) and with Bohr's predictions

What are orbital nodes

regions where probabilty of finding an electron = 0

angular nodes

equals l as a quantum number ranges from 0 to n-1

radial nodes

equation: n - l - 1

S orbital

0 angular nodes (l=0)

P orbital

1 angular node, can hold up to 6 in electron configuration

magnetic quantum number

The total number of 𝑚𝑙 values, 2𝑙+1, equals the number of orbitals per subshell.

Aufbau principle

add electrons in order of orbital energies, agrees with the pauli exclusion principle

First ionization energy

minimum energy needed to remove most weak electrons

D orbital

2 angular nodes, can hold up to 10 electrons in configuration

Filling order for atomic orbitals

1s << 2s < 2p << 3s < 3p < 4s < 3d < 4p

Inner electrons

electrons closest to the nucleus

Outer and valence electrons

electrons located in the outermost shell (energy level) of an atom. They are important for chemical bonding.

What does the period represent on the periodic table?

The quantum # of the outermost (valence) electron.

Periodic trends in atomic size

atomic size increases down a group and decreases across a period

Shielding effect

causes a lower effective charge than the atomic number, making electrons easier to remove

effective charge

nuclear charge an electron actually experiences.

Periodic trend for ionization energy

decreases in a group and increases across a period. N is further from the nucleus less energy is needed.

Electron Affinity for atoms

halogens have a large negative affinties, want an extra electron

Metallic character

metals tend to lose electrons to non metals, character increases down a group and decreases across a period

Positive ions

tend to be smaller (less electron-electron repulsion), electron is lost

negative ions

tend to be larger (more electron repulsion and sheilding) , electron is gained