Chapter 9 Lewis Structures Flashcards
Lewis model
A model for describing atoms and molecules that focuses on valence electrons. Atoms
will transfer or share electrons to achieve the valence electron configuration of the nearest noble gas.
Valence electrons
Electrons in the outermost principal shell of an atom
Octet rule
Atoms with eight electrons in their outermost shell are particularly stable.
Duet rule
Small atoms, such as hydrogen, helium, Beryrillium and lithium, are most stable with two valence
electrons in their outermost shell
Ionic compound
Cations and anions held together by electrostatic attraction
Molecule
Two or more non-metals held together by covalent bonds
Covalent bonds
Covalent bonds occur when electrons are shared between two atoms
Polyatomic ion
Group of atoms with an associated charge that acts as a single unit
(put brackets around these mainly because they have a charge; charged atoms need brackets and charge on outside)
Resonance
Two or more valid Lewis structures that are shown with double-headed arrows between
them to indicate that the actual structure of the molecule is intermediate between them
Expanded octet
A situation in which the most stable form of a molecule includes an atom with more
than 8 valence electrons. Elements in, and below, the third row of the periodic table exhibit expanded
octets. Occurs because d-orbitals are energetically accessible and can hold extra electrons
Formal Charge
Charge assigned to each atom in a Lewis structure. Allows us to determine which
Lewis structure is the most stable
Incomplete octet
A situation in which the most stable form of a molecule includes an atom with less
than 8 valence electrons. Occurs most commonly with Boron (stable with 6 electrons)
the calculation for formal charge
Calculation: valence electron - lone pair - # of covalent bonds
(this is to calculate formal charge of each atom in structure)
Atoms will transfer or share electrons to achieve the valence electron configuration of the nearest _____ ____
noble gas
