U2 Module 3: Geometry Flashcards
What are the properties of substances determined by?
The structure of its molecules
What 3 things is molecular structure dependent on?
- Atomic composition
- Atom connectivity
- Molecular geometry
What do Lewis Structures tell us?
How molecules are connected between each other
How do you determine what element will be the center atom in a bond?
Atom with the highest bonding capacity
How do you choose the central atom if they have the same boding capacity?
Use the atom with the larger mass
What are the two types of orbital bonds?
- Sigma
- Pi
Sigma Bond
Bonds that have head to head overlap
(think of as two ends of orbitals)
Pi Bond
Bonds that have side to side overlap
(next to each other)
What are the 3 limitations of the octet rule?
- Radicals
- Hypervalent
- Electron Deficient
Radicals
Bonded atoms that have an odd amount of electrons; 1 electron is alone.
What is an example of a radical species?
N bonded with O
What does the lewis structure for NO look like?
N double bonded to O
- N has 3 electrons (1 pair and 1 lone)
- O has 4 electrons (2 pairs)
Hypervalent
An atom that is bonded can have more than a full octet
- more than 8 electrons around it
What are the two common examples of hypervalent species?
P and S
- P can have 5 bonds
- S can have 6 bonds
Electron Deficient
Atoms do not have enough electrons to have a full valance shell.
What is an example of an electron deficient species?
Boron (B)
- Can only have 6 electrons (3 pairs)
Molecular Hybrids/Resonance
Each possible structure of a molecule is drawn out with a double arrow connecting.
What is changed in resonance structures?
Only the electrons, the main atoms do not move
- backbone stays the same
What happens to the electrons in molecules that display resonance?
The electrons are delocalized, which stabilizes the molecule.
(potential energy decreases)
Molecular Cations
Molecules that have a positive charge
- Loses one or more electron
Molecular Anions
Molecules that have a negative charge
- Gains one or more electron
What is the charge for a cation?
Positive
What is the charge for an anion?
Negative
How do you draw the lewis structure for cations and anions?
Have the lewis structure inside a pair of brackets, and add the charge to the upper right on the outside of the bracket.
What is the common bonding pattern of hydrogen?
One bond, no electrons
What is the common bonding pattern of carbon?
Four bonds
- Can be single, double, or triple
What is the common bonding pattern of nitrogen?
3 bonds and 1 electron pair (2 electrons)
- Can be single, double, or triple=
What is the common bonding pattern of oxygen?
2 bonds and 2 electron pairs (4 electrons)
- Can be single or double
Semi-Structural Formulas
The formulas for molecules are written in order of their separate bondingparts.
Line Structures
Structures used to represent complex molecular structures in simpler ways.
What represents a carbon in a line structure?
The ends/bends of lines
What is assumed is present in line structures?
Hydrogens bonded to the carbons
- Lone pairs too
Functional Groups
The distinctive arrangements of atoms
What is the distribution of electrons represented through?
Lewis structures
What is true about regions of high electron density around a single atom?
They will be located as far as possible due to electron repulsions (VSEPR)
How is the molecular geometry of complex molecules determined?
By analyzing the electron pair distribution around each of the atoms.
