Chem 1601 Test 2

Heisenberg’s uncertainty principle

You cannot simultaneously know both the exact position and the exact momentum (or velocity) of a quantum particle.

Constructive Interference

When waves from two sources meet in phase, creating a single wave with a larger amplitude

Destructive Interference

When waves from two sources meet out of phase, they create a single wave with a smaller amplitude

diffraction

The bending and spreading of waves when they pass through a small opening.

Wavefunction (Ψ)

Mathematical description of the quantum state of an isolated system or particle

Probability Density (Ψ²)

The likelyhood of finding an electron in 3D space around atomic nucleus

Energy Transitions in the atom

An atomic electron transition occurs when an electron jumps between discrete, quantized energy levels

Absorption (Jumping Up energy levels), Emission (Falling Down energy levels )

Radial Probability Density

The likelyhood of finding an electron in 3D space around atomic nucleus

Node

A region in space where wavefunction (Ψ) has a value of zero, no electrons can be found at this point

Radial Node

A node in radial wave function where spherical regions in atomic orbitals have a probability density of zero. # of radial nodes. n - l - 1.

Angular Node

A flat plane or cone that separates lobes. # of angular nodes = l

# of Total Nodes

# of Total Nodes = # of angular nodes + # of radial nodes = n - 1

Quantum Numbers

Numbers that quantize certain properties of the electron

Principal Quantum Number (n)

Positive integer associated with the energy and size of wave function of the electron at the highest point of the radial distribution plot. Energy levels of atom.

Orbital angular momentum Quantum Number (ℓ)

Quantized value that represents angular momentum of an electron. Range: 0 to n-1.

spdf notation

s: ℓ = 0, p: ℓ = 1, d: ℓ = 2, f: ℓ = 3, following orbitals: g, h, i, etc…

Magnetic Quantum Number m_l

Quantized value that specifies the spatial orientation of an atomic orbital along a designated axis Range: -ℓ to ℓ

Magnetic Spin Quantum Number m_s

Quantized value that represents spin (intrinsic angular momentum) of electrons. Range: -1/2, 1/2

Shell

All electrons with the same principal quantum number (n)

Subshell

A group of electrons within a shell with common orbital angular momentum quantum numbers (ℓ)

Orbitals

A three-dimensional region around an atomic nucleus where an electron is most likely to be found. # of orbitals per subshell = 2ℓ + 1

Shielding

The reduction of the attractive positive charge of an atom's nucleus on outer valence electrons due to the repulsive force of inner-shell (core) electrons.

Electron Penetration

Penetration describes the proximity to which an electron can approach the nucleus.

Electron Configuration

Distribution of electrons of an atom or molecule among its atomic or molecular orbitals.

Aufbau Principle

Orbitals must be filled from lowest to highest energy

Pauli Exclusion Principle

No two electrons can have the same 4 quantum numbers

Hund’s Rule

Every orbital in a subshell must be occupied with one electron of the same spin before any one orbital is occupied with 2 electrons.

Degeneracy

When two or more distinct quantum states or atomic orbitals have the exact same energy level

Effective Nuclear Charge

The charge experienced by the electron after accounting for the repulsion of inner core electrons. Equation: Z_eff = z - s (z = protons, s = shielding electrons)

Ground State

Its lowest possible energy and most stable arrangement within an atom

Excited State

Occurs when it absorbs a specific amount of energy and jumps from its normal, lowest-energy position (the ground state) to a higher-energy orbital

Valence Electrons

Electrons in outermost shell that participates in chemical bonding


Identify Valence Electrons:

• Main-Group Elements (s) and (p) blocks): Count all the electrons in the subshells with the highest (n) value (s) and (p) orbitals.

• Transition Metals (d) block): Count the outermost (s) electrons plus the unfilled ((n-1)d) electrons

Core Electrons

Electrons closest to nucleus that do not participate in chemical bonding. all electrons that are not valence electrons.

Isoelectronic

Ions / Elements having the same number of electrons and same electron configuration.

Diamagnetic

Paired electrons in orbitals. Repelled by a magnetic field.

Paramagnetic

Unpaired electrons. Attracted to a magnetic field.

Periodic Trend

Predictable patterns in the properties of elements as you move across periods (rows) or down groups (columns)

Atomic Radii

Atomic Radius increases as you go down and to the left of the periodic table.

Ionic Radii

Cations (Atom⁺) are smaller than their neutral parent atoms. Anions (Atom^-) are larger than their neutral parent atoms. Anions are mostly bigger than cations

Ionization Energy

The minimum amount of energy required to remove an electron. Increases as you go up and to the right of the periodic table

Electron Affinity

The neutral atom's likelihood of gaining an electron. Increases in magnitude up and to the right of the periodic table. Highest electron affinity: Cl.

Metallic Character

Increases down and to the left of the periodic table

Bond order

The number of electron pairs shared shared between 2 atoms. Single bond has bond order of 1, double bond has a bond order of 2, etc

Lewis Structures

Method of drawing atoms, Each valence electron is represented by a dot and each bond is represented by line.

Octet Rule

Most main group elements gain, lose, or share electrons in order to achieve full valence shell of 8 electrons or 4 valence orbitals (1 s orbital and 3p orbitals)

Resonance Structures

Lewis drawings differing in the position of bonding and non-bonding electrons. Represents the electron configuration of a molecule.

Resonance contributor

A Lewis structures representing the same molecule or polyatomic ion, differing only in the arrangement of electrons, which collectively describe the actual electron distribution of the hybrid structure.

delocalized

Electrons in a molecule, ion, or metallic lattice that are not confined to a single atom or bond, but are spread out over three or more adjacent atoms.

dipole moment (mu)

A measurement of the net separation of positive and negative electrical charges within a system; it quantifies its overall polarity.

mu = Q * r

q: the magnitude of the separated electric charge

r: distance between charge centers

Organic Compounds

Chemical compounds built around chains of carbon atoms

Functional Groups

a specific cluster of atoms within a molecule that gives that molecule its characteristic chemical reactions, physical properties, and reactivity, no matter what other atoms are present

Alkane

Alkene

Alkyne

Aromatic

Alcohol

Ether

Aldehyde

Ketone

Carboxylic Acid

Ester

Amine

Amide

nitrile

Ground State electron configurations EXCEPTIONS

Single bond bond order, bond length, bond strength

bond order: 1
bond length: longest
bond strength: weakest

Double Bond

bond order: 2

bond length and bond strength: between single and triple

Triple Bond

bond order: 3
bond length: shortest
bond strength: strongest