Ionic Bonding
An ion contains 20 protons and 18 electrons. What is its symbol?
Ca²⁺
How many shared pairs of electrons are found in one molecule of oxygen, O₂?
2
Which allotrope of carbon contains delocalised electrons that can move through the structure?
Graphite (or graphene)
What particles carry electrical charge through a metal?
Delocalised electrons.
What size range defines a nanoparticle?
1-100 nm
What is the formula of aluminium sulfate?
Answer: Al₂(SO₄)₃
How many covalent bonds are present in a methane molecule?
4
Why is diamond used in cutting tools?
It has a giant covalent structure with strong covalent bonds throughout, making it extremely hard.
Why are metals malleable?
Layers of positive ions can slide past one another while metallic bonding remains intact.
Why are nanoparticles often used as catalysts?
They have a very large surface area to volume ratio.
What is the formula of the compound formed from Mg²⁺ ions and nitrate ions?
Mg(NO₃)₂
Both hydrogen chloride and sodium chloride contain chlorine. Which is simple molecular and which is ionic?
HCl = simple molecular; NaCl = ionic
Why can graphite conduct electricity whereas diamond cannot?
Graphite has delocalised electrons; diamond does not.
What type of structure is found in copper?
Metallic lattice.
Why can titanium dioxide nanoparticles be used in sunscreen whereas ordinary titanium dioxide would be unsuitable?
Nanoparticles are transparent on the skin while still absorbing/blocking UV radiation.
Why does a giant ionic lattice not conduct electricity when solid but conduct when molten?
Ions are fixed in position in a solid but free to move when molten.
A substance has a melting point of −104°C, a boiling point of −34°C and does not conduct electricity. What type of structure does it most likely have?
Simple molecular.
Graphite is softer than diamond. Why does graphite still have a very high melting point?
Melting requires breaking strong covalent bonds within the layers, not overcoming the weak forces between layers.
Why does sodium have a lower melting point than aluminium, even though both are metals?
Al³⁺ has three times the positive charge of Na⁺, leading to stronger attraction to the delocalised electrons and therefore stronger metallic bonding.
What are the 2 key parts of a composite called?
Reinforcement and Matrix
Magnesium oxide and sodium chloride are both ionic. Which has a higher melting point and why?
Mg²⁺ and O²⁻ ions have greater charges, creating stronger electrostatic attractions that require more energy to overcome.
Carbon dioxide and silicon dioxide both contain one atom bonded to two oxygens. Why is one a gas at room temperature while the other has a melting point above 1600°C?
CO₂ is simple molecular with weak intermolecular forces; SiO₂ is giant covalent with strong covalent bonds throughout the structure.
Put C₆₀, graphite and diamond in order of increasing melting point and explain your reasoning. Give the other name for C₆₀.
C₆₀ < graphite ≈ diamond. C₆₀ is molecular; graphite and diamond are giant covalent.
A substance has:
What type of structure does it most likely possess, and why?
Giant covalent; many strong covalent bonds but no free ions or delocalised electrons.
Two silver catalysts have the same mass. One consists of 1000 nm particles and the other of 10 nm particles. Which should be the more effective catalyst and why?
The 10 nm particles because they provide a much greater surface area-to-volume ratio and expose more active sites.