Unit 2 : GenChem1

Valence Electrons

Electrons in the outermost energy shell

Core Electrons

All other electrons

S-orbital

First energy shell (1 orbital)

P-orbital

Second energy shell (3 orbitals + S-orbital)

D-orbital

Third energy shell (5 orbitals + P-orbital + S-orbital)

Energetically Degenerate

Each orbital is the same energetically

Electronegativity

The tendency of an atom to hold onto its electrons tightly

Covalent Bonds

Sharing of two electrons between two atoms

Intermolecular Forces

Forces between molecules that attract them to each other (weaker than covalent bonds)

Dipole

A separation of charge

Polar Covalent Bonds

Covalent bond between two elements with different electronegativities

Nonpolar Covalent Bonds

Covalent bond between two elements with the same electronegativity

London Dispersion

Attractive force between instantaneous dipoles, can be used by every molecule and is determined by surface contact

Instantaneous Dipole

A dipole created by the random movement of electrons

Dipole-Dipole

Attractive force between permanent dipoles in different molecules, required polar covalent bonds

Hydrogen Bond

Special case of dipole-dipole; attractive forces between a hydrogen bonded to an electronegative heteroatom and a pair of nonbinding electrons on a different electronegative heteroatom

Donor Sites

Partially positively charged H that can form hydrogen bonds

Acceptor Sites

The remaining lone pairs of electrons on a partially positively charged heteroatom

Heteroatom

Any atom that is not a Carbon or Hydrogen

Boiling Point

The temperature where there is enough energy to overcome the intermolecular forces that are holding the molecules tightly together

Solubility

The ability of a solute to dissolve in a solvent; the solvent must be able to surround the solute, the better able the solvent can make strong intermolecular forces around the entire solute, the more soluble it will be

Saturated

When the amount of a solvent is equal to the amount of solute

Chromatography

Separation of molecules based on their interactions with a stationary and mobile phase

Normal Phase Chromatography

Polar stationary phase, nonpolar mobile phase

Reverse Phase Chromatography

Nonpolar stationary phase, polar mobile phase

Isomer

Molecules with the same molecular formula but are non-superimposable

Constitutional/Structural Isomer

Isomers with different connectivity

Stereoisomer

Same molecular formula, same connectivity, not superimposable

Geometric Isomer

Stereoisomers that differ across a RIGID PLANE (cis- / trans-)

Rigid Plane

A double bond or ring structure