FINAL - SECTION 3 Flashcards
Ionic bond
Electrons TRANSFERRED from 1 atom to another (nonmetal + metal)
Covalent bond
Electrons SHARED between atoms (nonmetal +nonmetal)
Lewis symbol
Dots around symbol representing valence electrons
Octet rule
Tendency for atoms to want 8 electrons in outer shell
Duet rule
H and He can only have up to 2 electrons in valence
Single bond
Represents 2 electrons
Double bond
Represents 4 electrons
Nonpolar covalent bond
Electrons shared EQUALLY between atoms of bond and NO separation of charge
Polar covalent bond
Electrons shared UNEQUALLY between atoms of bond and has separation of charge (S-/S+)
Nonpolar molecule
Symmetric with no unshared electrons
Polar molecule
Asymmetric and contain LP on central atom
Electronegativity
Measures pull of electrons
What does a high electronegativity mean
It means that it is stronger (greater pull of electrons)
Electronegativity trend
Increase left to right and decrease top to bottom (fluorine greatest)
How is the electronegative atom described
S-
Electronegativity arrows
Arrow goes from S+ –> S-, but if arrows are opposite then they cancel out and are nonpolar
Electronegativity trend
- Difference less than 0.4 = nonpolar covalent bond
- Difference between 0.4-2.0 = polar covalent bond
- Difference greater than 2.0 = ionic bond
Formal charge
- Assigns charges to individual atoms
- FC = non bonding electrons - # of bonds
Reasonance structure
- Structures with equal correctness
- Least FC preferred
- Only electrons and bonds move (NOT ATOMS)
- Single bond = 3 LP (6 e-)
- Double bond = 2 LP (4 e-)
- Triple bond = 1 LP (2 e-)
If + necessary on resonance structure…
Should be on the least electronegative atom
If - necessary on resonance structure….
Should be on the most electronegative atom
Exceptions to octet rule
- Free radicals: Molecules with unpaired electrons
- Incomplete octet: Some atoms form 3 bonds instead of 4
- Expanded valence: Elements in third row and below can have more than an octet
