Ionic Bonding
What charge does a magnesium ion carry after bonding?
+2
What happens to electrons in a covalent bond?
Sharing of electrons between atoms.
Rank the following from weakest to strongest:
Dipole-dipole, London Dispersion Forces, Hydrogen Bonding
LDFs < Dipole-dipole < Hydrogen Bonding
In a redox reaction, can oxidation occur alone?
No, oxidation and reduction occur together.
What causes a bond to be polar?
A difference in electronegativity
Why are ionic compounds electrically neutral overall?
Total positive charge equals total negative charge in the lattice.
Which element almost always forms four covalent bonds?
Carbon
Which IMF is present in all molecules, including nonpolar ones?
London dispersion forces.
What happens to oxidation state during reduction?
Decreases.
Why is water polar even though it has nonpolar bonds?
Its bent shape creates a net dipole
Which factor most strongly increases lattice energy: higher charge or larger ionic radius?
Higher ionic charge (charge has a greater effect than size).
Which bond is shorter: N≡N or N=N?
N≡N
Which element must hydrogen be bonded to for hydrogen bonding to occur?
Flourine, Oxygen, or Nitrogen
Find the oxidation number of of S in H2SO4.
2(+1) + x + 4(-2) = 0
2 + x - 8 = 0
x = +6
Explain why a molecule with polar bonds be nonpolar overall
If the molecule geometry is symmetrical, the bond dipoles cancel out and result in a zero net dipole moment.
Why do ionic compounds conduct electricity when molten but not when solid?
Ions are free to move when molten allowing them to conduct electricity.
Why does increasing the number of shared electrons increase the bond dissociation energy?
More shared electrons increase bond dissociation energy because stronger electrostatic attraction between nuclei and electrons makes the bond harder to break.
Which has the higher boiling point: NH₃ or CH₄?
NH₃ due to the hydrogen bonding.
Which species is oxidized when Zn reacts with Cu²⁺?
Zinc
Explain why NH3 is polar but BF3 is nonpolar.
NH₃: lone pair makes it polar
BF₃: symmetrical shape cancels dipoles
Explain why Al2O3 has a higher melting point than MgO.
Al2O3 has a higher melting point than MgO because Al3+ has a higher charge and smaller size than Mg2+, giving a stronger electrostatic attraction in the lattice.
Explain why graphite conducts electricity but diamond does not, even though both are made of carbon.
Graphite: three bonds per carbon, has delocalized electrons which allow conductivity.
Diamond: four bonds per carbon, all electrons are localized resulting in no conductivity.
Explain why I₂ is a solid at room temperature, while Cl₂ and Br₂ are gases or liquids.
I₂ has stronger van der Waals forces, so it is solid at room temperature, whereas Cl₂ and Br₂ have weaker van der Waals forces and exist as gases or liquids.
The reaction below occurs in acidic solution:
MnO4- + SO32- −> Mn2+ + SO42−
Determine the oxidation number of sulfur in both sulfur-containing species and state whether sulfur is oxidized or reduced.
3×(−2)=−6
The overall charge of the ion is –2, so:
Oxidation number of S + (−6)=−2
Oxidation number of sulfur in SO32- =+4
4×(−2)=−8
The overall charge of the ion is –2, so:
Oxidation number of S + (−8) = −2
Oxidation number of sulfur in SO42- = +6
Sulfur goes from +4 --> +6
Therefore, Sulfur is oxidized
Consider the molecules H₂O, CO₂, and CH₄.
Rank these molecules in order of increasing polarity and explain your reasoning.
Order of increasing polarity:
CH4 < CO2 < H2O
CH₄ is nonpolar (symmetrical tetrahedral, no net dipole)
CO₂ is nonpolar (linear, bond dipoles cancel)
H₂O is polar (bent shape creates a net dipole)