Ionic Bonds
What types of elements typically form ionic bonds?
Metal & nonmetal
What types of elements typically form covalent bonds?
Nonmetals
If a bond has a dipole moment, what must you draw next to that bond?
Vector
What elements are required to form a hydrogen bond?
Hydrogen + Nitrogen
Hydrogen + Oxygen
Hydrogen + Fluorine
What is the molecular structure of metals composed of?
How are cations formed?
What type of charge do cations carry?
How are anions formed?
What type of charge to anions carry?
Cations are formed through the loss of electrons
Cations carry a positive (+) charge
Anions are formed through the gain of electrons
Anions carry a negative (-) charge
What happens to electrons in a covalent bond?
Electrons are shared in a covalent bond
How can a molecule have polar bonds, but be nonpolar overall?
1. Molecular geometry is completely symmetrical
2. Dipole moment vectors cancel each other out
What 2 things are necessary to form a hydrogen bond?
1. Hydrogen must have a partial positive charge (δ+)
2. The atom that is interacting with hydrogen must have an unbonded lone pair
Explain what it means for an electron to become "delocalized"
A delocalized electron has detached from its original atom and can move freely through the sea of electrons
What happens to electrons in an ionic bond?
Electrons are transferred in an ionic bond
What is the key indicator of a polar covalent bond?
Unequal sharing of electrons
1. How does surface area influence the strength of London Dispersion Forces?
2. What kind of molecules typically have a higher surface area? What kind of molecules typically have a lower surface area?
1. Higher surface area = stronger LDF
2. Straight chain molecules typically have a higher surface area than branched molecules
What are the 3 molecules commonly found to exhibit hydrogen bonding?
1. Ammonia (NH3)
2. Water (H2O)
3. Hydrogen Fluoride (HF)
List the 3 factors that affect the strength of metallic bonds.
1. # of delocalized electrons
2. Charge of the metal (+1, +2, +3)
3. Atomic radius of the metal
Explain the electron transfer in the formation of the following molecule:
KBr
Potassium (K) is less EN (wants to lose its valence electron)
Bromine (Br) is more EN (wants to gain one more electron to complete its valence shell)
Why do polar covalent bonds occur?
What charges are associated with each atom in a polar covalent bond?
Differences in EN values
The more EN atom will be partially negative (δ-)
The less EN atom will be partially positive (δ+)
List the 3 molecular geometries that are completely symmetrical.
1. Linear
2. Trigonal planar
3. Tetrahedral
Why is water considered an ideal hydrogen bonded system?
There are exactly the right numbers of hydrogens and lone pairs for each one of them to be involved in hydrogen bonding.
What does a stronger metallic bond tell you about the melting & boiling points of a metal?
Stronger bonds = higher melting & boiling points
Why do ionic compounds dissolve easily in water?
The polarity of the water molecules shields the anions (-) from attracting the cations (+)
Rank the 3 types of covalent bonds in order from strongest to weakest and explain why.
Triple bond is the strongest because it has the shortest bond length. There are 6 bonded electrons being shared
Double bond has a longer bond length than triple bonds, but a shorter bond length than single bonds. There are 4 bonded electrons being shared
Single bond is the weakest because it has the longest bond length. There are only 2 bonded electrons being shared
Rank all bond types & intermolecular forces from strongest to weakest.
1. Ionic
2. Covalent
3. Metallic
4. Hydrogen
5. Dipole-dipole
6. London Dispersion Forces
Explain why ammonia (NH3) and hydrogen fluoride (HF) are limited in their hydrogen bonding capabilities.
1. Ammonia (NH3) is limited by nitrogen only having one lone pair
2. Hydrogen fluoride (HF) is limited by a shortage of hydrogen atoms
Why are metallic bonds stronger in transition metals compared to metals in groups 1 and 2?
Transition metals can involve electrons from the s orbital and the d orbital in the delocalization process
More delocalized electrons = stronger attractions