For video lectures on how to create a Lewis structure, and why we would do it, click here.
- Lewis structure- a diagram of a molecule showing how the valence electrons are arranged among the atoms in the molecule
- Duet rule- ie Hydrogen, share two electrons to have a filled valence shell
- Octet rule- the observation that atoms of nonmetals form the most stable molecules when they are surrounded by 8 electrons
- Bonding pair- an electron pair found in the space between two atoms
- Lone (unshared) pair- an electron pair that is localized on a given atom; an electron pair not involved in bonding
- Single bond- a bond in which two atoms share one pair of electrons
- Double bond- a bond in which two atoms share two pairs of electrons
- Triple bond- a bond in which two atoms share three pairs of electrons
- Resonance- a condition occurring when more than one valid Lewis structure can be written for a particular molecule. The actual electron structure is represented no by any one Lewis structure but by the average of all of them.
- Resonance structure- Various Lewis structures for the same molecule
- Acid- a substance that produces hydrogen ions in aqueous solution; proton donor; a molecule with one or more H+ ions attached to an anion. The rules for naming acids depend on whether the anion contains oxygen
Lewis Structures
- To learn to write Lewis structures.
- Electrons in the highest principle energy level of an atom are called the valence electrons. Bonding involves just the valence electrons of atoms. Lewis structures show how the valence electrons are arranged among the atoms in the molecule.
- The most important requirement for the formation of a stable compound is that the atoms achieve noble gas electron configurations.
- Carbon, nitrogen, oxygen, and flourine almost always obey the octet rule in stable molecules.
- Lewis structures show only valence electrons. The group number gives the total number of valence electrons ie group 6 elements have 6 valence electrons.
- In writing Lewis structures, keep the following things in mind:
- We must include all the valence electrons from all atoms. The total number of electrons available is the sum of all the valence electrons from all the atoms in the molecule.
- Atoms that are bonded to each other share one or more pairs of electrons.
- The electrons are arranged so that each atom is surrounded by enough electrons to fill the valence orbitals of that atom. This means two electrons for hydrogen and eight electrons for second row nonmetals.
- Steps for Writing Lewis Structures:
- Obtain the sum of the valence electrons from all the atoms. Do not worry about keeping track of which electrons come from which atoms. It is the total number of valence electrons that is important.
- Use one pair of electrons to form a bond between each pair of bound atoms. For convenience, a line instead of a pair of dots is often used to indicate each pair of bonding electrons.
- Arrange the remaining electrons to satisfy the duet rule for hydrogen and the octet rule for each second-row element.
Lewis Structures of Molecules with Multiple Bonds
- To learn how to write Lewis structures for molecules with multiple bonds
- Always check the total number of electrons and the octet rule for each atom. Use shared bonds to make sure each atom is surrounded by 8 electrons, up to triple bonds.
- When more than one Lewis structure can be written for the same compound, the structures are called resonance structures.
Naming Binary Compounds that Contain Only Nonmetals (Type III)
- To learn how to name binary compounds containing only nonmetals.
- Rules for Naming Type III Binary Compounds
- The first element in the formula is named first, and the full element name is used.
- The second element is named as though it were an anion.
- Prefixes are used to denote the numbers of atoms present. (prefixes listed pg 122)
- The prefix mono- is never used for naming the first element.
- Water and ammonia are always referred to by their common names.
Related posts:
Top Articles