Chapter 3 Bonding Chem rxns involve the transfer of electrons which are important non nuclear constituents of an atom o Each electron may be described by a wave function whose magnitude varies from point to point in space Schrodinger Wave Equation H E o wave function H Hamiltonian operator E energy Maximum Minimum Each point in space can be represented by spatial coordinates x y z Node Point which the wave changes its phase Generated as the amplitude of the wave changes from to Wave functions for electrons of diff energies can be described in terms of the of nodes If there are 0 nodes there s no change in sign and the wave function remains o Electron cloud is spherically shaped S orbitals 1 node o Electron cloud is dumb o bell shaped P orbitals 3 identical p orbitals px py pz Three p wave functions that describe three diff places where an electron has the same E so the p orbitals are said to be degenerate Heisenberg Uncertainty Principle the position and 2 nodes d orbitals o momentum of an electron cannot be simultaneously specified Its only possible to determine the probability that an electron will be found a particular pt relative to the nucleus o A charge cloud represents the region of space where we are most likely to find the electron in terms of the x y z coordinates Charge clouds are orbitals Orbitals w lower principle quantum s are more stable lower in E o Means than an electron in a 1s orbital is lower in E than an electron in a 2s orbital and so on B c 2s electrons are found further from the nucleus and it takes more E to hold a 2s electron to the nucleus than to hold a 1s electron E levels represent the region in space where electrons are found relative to the nucleus o Diff E levels are associated w each type of electron shell so there are diff types of orbitals Chapter 3 Bonding 1s 2s 3s 4s etc They are similar in shape but differ in E distance from nucleus o Electronic Configuration the description of the way electrons are distributed in the atomic orbitals of an element Shows type quantum level and of electrons Chem rxns involve the gain loss or transfer of electrons particularly valence electrons o Valence Electrons those found in the outermost orbitals furthest from nucleus More weakly bound than electron in orbitals closer to the nucleus The periodic table is arranged more or less by chem reactivity using the of electrons in the outermost shell of the element and the E of those valence electrons o Elements are arranged according to their valence orbitals Organometallic molecules composed of a metal w 1 attached C atoms The electron config of each element is described by the order in which the various orbitals fill as the of electrons increases for each element of the periodic table o Each indiv orbital can hold no more than 2 electrons o Electrons have the property of spin associated w magnetic dipole Electrons spin in opposite directions spin paired o A single orbital containing 2 electrons filled orbital If 2 electrons occupy 1 orbital spin pairing is lower than if 2 electrons of the same spin are forced to occupy the same orbital o Pauli Exclusion Principle if there are several orbitals of equal E such as all 3 2p orbitals each orbitals will fill w 1 electron before any orbital contains 2 o Attempting to fill one orbital w 2 spin paired electrons before filling the next orbital would require more E Electrons have like charges and 2 electrons will repel if they are in the same orbital so electrons fill empty orbitals first to conserve E Aufbau Principle orbitals are filled w electrons in ascending order of orbital E until all available electrons have been used 1s 2s 2p 3s 3p 4s 3d 4 p etc Electrons in an element or in a bond b w 2 atoms are assumed to reside in orbitals o A bond occurs b w 2 atoms and the electrons in that bond are associated w a molecule not a single atom o B c bonds are found in molecules the orbitals used to form a bond in a molecule are different from the orbitals found in elemental atoms o The nucleus is the convergence point of the tricoordiante system A chem rxn b w atoms or groups of atoms will usually produce new combos of atoms held together by chemical bonds Chapter 3 Bonding electrons o Resulting bonds b w atoms is composed of 2 o Covalent Bond formed by mutual sharing of valence o electrons b w 2 atoms Sharing of electron density holds atoms 2gether Ionic Bond transfer of electrons from atom to another where atoms are held 2gether by electrostatic force Results in ions and To participate in an ionic bond an atom or group must be either electron rich or electron poor and have a charge Octet Rule max of 8 electrons can occupy the valence shell o Atoms like to have a noble config having a filled outer electron chell b c they are particularly stable and therefore low in E and low in reactivity o There s an energetic preference for transferring electrons to attain the noble gas config During electron transfer processes transfer of the charged electron from Li leads to Li rather than Li b c Li is more stable requires less E to form E gained or lost for an atom is a measurable quantity o Ionization Potential E required for the loss of electrons from an atom o Electron Affinity E required for the gain of electrons into an atom The bonds in molecules that contain C are usually formed by sharing electrons w one another atom in what s known as a covalent bond rather than a complete transfer of electrons o Covalent bonds are more E favorable for certain atoms elements than ionic bonds o Atoms in a molecule that contain C will react w another molecule to change the groups attached to C So electron transfer is not w elemental C but rather a C containing molecule o The orbitals for atomic C are diff from the orbitals for covalent C in a molecule C in the element is diff from the C in a molecule When electrons are concentrated in orbitals on a single atom the electrons are said to be localized on that atom o When an atom is part of a covalent bond however it shares electrons w the other atom The electrons in the bond aren t localized on one atom but rather are shared by both atoms and concentrated b w the atoms o In a molecule the electrons reside in diff orbitals are known as molecular orbitals mix of atomic orbitals hybridization o Hybrid orbitals have directionality the shared electron density will be directed toward one atom in the bond the negative atom o A covalent bond is described as the overlap of two hybrid orbitals Sigma Bond a bond