4.3 Covalent Bonding Flashcards
When does covalent bonding occur?
When atoms share electrons.
What is a covalent bond?
A covalent bond is the electrostatic attraction between the shared pair of electrons and the nuclei of the atoms making up the bond.
What are single bonds, double bonds and triple bonds made up of?
A single bond is made up of 1 shared pair of electron, a double bond is made up of 2 shared pairs of electrons, a triple bond is made up of 3 shared pairs of electrons.
If the same atoms are involved what is the order of types of bonds for bond strength?
Single bonds < double bonds < triple bonds
If the same atoms are involved what is the order of types of bonds for bond length?
Single bonds > double bonds > triple bonds
How does the attraction differ for different types of bonds?
The attraction of the two nuclei for two electron pairs (4 electrons) in a double bond is greater than the attraction for one electron pair (2 electrons) in a single bond.
What is a coordinate bond?
A type of covalent bond where both electrons come from the same atom.
What is a Lewis structure?
A diagram showing all the valence (outer shell) electrons in a molecule or ion.
What is the octet rule?
The tendency of an atom (with the exception of H) in a molecule or ion to have 8 electrons in there outer shell.
What are the rules for working out a Lewis structure?
Make sure that the outer atoms have 8 electrons (octet) in their outer shell (except hydrogen which should have 2). This can be sone by forming single bonds, double bond, triple bonds and or adding/removing electrons for ions.
If the central atom is from period 2 it should have no more than 8 electrons in its outer shell. It shod generally (but not always) have 8 electrons in its outer shell.
If the central atom is from period 3 it may have up to 18 electrons in its outer shell.
What are resonance structures?
Structures where the only difference between them is where we put the double bond and lone pairs is approbate. The individual lewis structures are called resonance structures.
The actual structure of a molecule/ion can be described as a HYBRID of these structures.
How can the shape of molecules or ions be predicted?
Using valence shell electron pair repulsion theory.
What does the shape of molecules depend on?
The number of electrons domains in the outer shell of the central atom.
What could an electron domain be?
A lone pair.
An electron pair that makes up a single bond.
The electron pairs together that make up a multiple bond - a double bonds or a triple bond count as one electron domain.
What do electron domains in the outer shell of the central atom do?
Electron domains in the valence (outer shell) of the central atom in a molecule repel each other and will therefore take up positions in space to minimise these repulsions (to be as far apart as possible).
