> See also: > - [[Molecular Structure]] # Electrons Electrons are "contained" ## Electron Orbitals Electrons are not ## Chemical Bonds In Terms of Orbitals - **Molecular Orbital (MO):** orbital formed via overlap of atomic orbitals *between* separate atoms - Orbitals are conserved; combining two atomic orbitals results in two new molecular orbitals ### Molecular Orbital Classifications There are two classifications of molecule orbitals based on their *symmetry*: **Sigma** ($\sigma$) **Pi** ($\pi$): molecular orbital lacking a rotational axis of symmetry ## Electron Configuration ![[Electron Orbital Diagram.png|300]] Every box in an orbital diagram represents an **orbital**. Columns with the same level are called a **sublevel**. - These are represented by a single letter: (s, p, d, f) **Orbital:** The region of space around the nucleus with the highest probability of finding an electron. > Higher orbitals are less stable > **Stability:** Full Orbital > Half Orbital > Empty Shell > The electron configuration can be written as the *full configuration* or in the *short hand* Electrons are more stable at full orbitals (see orbital diagrams), this can be used to predict [[electron affinity]] or [[ionization]] energy of "middle" atoms (elements near the center of [[the periodic table]]) --- ![[Periodic Table Orbital Shells.png|400]] --- # Rules of Electron Configurations - **Aufbau Principle** *(”to build up”)*: - **Hund’s Rule:** The lowest-energy configuration for an atom with electrons within a set of degenerate orbitals is that having the maximum number of unpaired electrons. Two or more molecules are **isoelectronic** if they share the same electron configuration ## The Octet Rule > [!abstract] The Octet Rule > We try to share valence electrons ($e^-$) so that each atom has 8 valence electrons > - Electrons inside covalent bonds count towards both atoms > - Lone-Pair electrons count towards a single atom > > > ###### Octet Rule Violations > The octet rule mostly applies to outer atoms. It’s more common for the central atoms of a structure to exceed the octet rule. ## Electron Shielding In response to an external magnetic field, electrons circulate around protons and produce an induced magnetic field. The induced field 1) repels the external field and 2) shields protons from it. Greater densities of electrons offer greater proton shielding. Lesser densities of electrons offer less proton shielding. Lesser shielded protons may be referred to as deshielded.