Chemical Bonding Flashcards
Intramolecular forces
Hold atoms together. Ionic and covalent bonds
Intermolecular forces
Weaker forces between molecules
Octet rule
An atom tends to bond with other atoms until it has eight electrons in its outermost shell
Ionic bonds
One or more electrons from an atom with a smaller IE are transferred to an atom with greater EA. Ions held together by electrostatic forces.
EN difference >1.7
Form crystal lattices of arrays of + and - ions.
High melting and boiling points. Conductive
Covalent bonds
Electron pair shared between two atoms.
Low melting and boiling points. Not conductive.
Bond order
The number of shared electron pairs between 2 atoms
Bond length
The average distance between the two nuclei of the atoms involved in a bond. Decreases with increasing number of shared electron pairs
Bond energy
The energy required to separate two bonded atoms. Increases with increasing number of shared electron pairs
Bonding electrons
The shared valence electrons of a covalent bond
Lone Pairs
Unshared electrons pairs
Lewis structure
A notation to represent the bonding and nonbonding electrons in a molecule
Formal charge
The difference between the number of electrons in an atom in a Lewis structure and the number of valence electrons of the free atom.
fc = v - 1/2Nbonding - Nnonbonding
Resonance structures
A hybrid of more than one Lewis structure for a single molecule unable to be described fully with only one Lewis structure
Polar covalent bond
Between atoms with small EN differences, 0.4 - 1.7. Creates partial charges
Dipole moment
The product of the charge magnitude and distance between two partial charges: u = qr Debye units (C m)
Nonpolar covalent bond
Between atoms that have the same EN
Coordinate covalent bond
Shared electron pair comes from the lone pair of one atom in the molecule
Lewis acid
Accepts an electron pair
Lewis base
Donates an electron pair
Valence shell electron-pair repulsion (VSEPR)
Uses Lewis structures to predict geometry of covalently bonded molecules. Atoms arrange to minimize replusion
Molecular orbital
The probability of finding the bonding electrons
Obtained by adding the wave functions of atomic orbitals
Bonding orbital
When the signs of two atomic orbitals are the same
Antibonding orbital
When the signs of two atomic orbitals are different
Sigma bond
When two orbitals of different atoms overlap head-to-head
Pi bond
When two p orbitals of different atoms interact
van der Waals forces
The intermolecular forces due to interactions of ions or hydrogen bonding
Dipole-dipole interactions
Polar molecules orient themselves such that the positive region is close to the negative region of another to be energetically favourable
Hydrogen bonding
Particularly strong dipole-dipole interactions when a H is covalently bound to F, O or N. The positively charged H interacts with the partially negative charged electronegative atom
London dispersion forces
Unequal sharing of electrons cause rapid polarization and counterpolarization of the electron cloud and formation of short-lived dipoles to interact with the electron clouds of neighbouring molecules
