Ionic bonding
Give the definition of ionic bonding.
The electrostatic attraction between oppositely charged ions.
Give the definition of covalent bonding.
The electrostatic attraction between a shared pair of electrons and the positively charged nuclei.
Explain what an allotrope is and give an example.
Ozone and oxygen.
Any carbon allotropes.
Name three types of intermolecular forces.
London (dispersion) forces
dipole-dipole attraction
hydrogen bonding
Give the definition of metallic bonding.
The electrostatic attraction between a lattice of positive ions and delocalised electrons.
Give the formula of a phosphate ion.
PO43-
What is the relationship between bond length and bond strength?
Short bonds are strong bonds OWTTE.
Explain the octet rule. Which two atoms form stable compounds with incomplete octects?
Tendency of atoms to gain a valence shell with a total of 8 electrons. Be and B are exceptions.
Describe the three intermolecular forces and their comparative strengths.
London (dispersion) forces: attraction between induced or temporary dipoles of non-polar molecules.
Dipole-dipole attraction: attraction between permanent dipole of polar molecules.
Hydrogen bonding: attraction between slightly positive hydrogen bonded to very electronegative atom (F, N, O) and the slightly negative F, N or O from another molecule.
Name three applications of specific metal alloys.
Any valid responses.
Give the formula of sodium carbonate.
Na2CO3
Explain how a polar bond is formed.
If atoms with different electronegativity values bond together, one of the will pull on the electrons in the bond more strongly and will therefore have a partial negative charge, while the other will have a partial positive charge. This results in a polar covalent bond.
Explain why graphite conducts electricity.
Each carbon atom in the graphite structure is bonded to three others meaning there is a free, delocalised electrons for each C. These can conduct electricity through the layers.
methoxymethane (CH3-O-CH3) has a boiling point of -23C, ethanol has a boiling point of +79C. Explain the difference.
ethanol forms hydrogen bonds and methoxymethane does not. Hydrogen bonding is stronger than dipole-dipole attraction. So ethanol requires more energy to overcome the intermolecular forces between molecules and evaporate.
Explain why alloys are usually more chemically stable, stronger and more resistant to corrosion than pure metals.
In an alloy, there is more than one type of metal. This protects the metal from reacting and corroding. Due to the presence of different size cations in the lattice of an alloy, the layers of metal ions cannot slide over each other easily. Therefore, they are stronger and less malleable than pure metals.
Na2O has a melting point of 1132C, MgO of 2800C. Explain the difference making reference to their structure and bonding.
Both are ionic compounds but Mg2+ has a higher charger than Na+ , it also has a smaller ionic radius. Therefore, the electrostatic attraction between the ions is larger in MgO than in Na2O and it requires more energy to break the bonds.
Give an example of two polar bonds and explain which one is most polar.
Any valid example.
Give three examples of molecules with three different shapes. Give the structure of the molecule, the name of the structure and the approximate bond angles.
Any three valid and correct molecules according to VSEPR theory.
Explain why water expands when it freezes to become ice.
Explain the trend in melting points of metals down the group.
Melting points decrease down the group as the strength of the metallic bond decreases as the size of the cations increase. This reduces the attraction between the delocalised electrons and positive charges.
You are given two white solids and are told that one of the is an ionic compound. Describe three tests you could carry out to determine which it is.
Test the melting point: ionic solids have high melting points.
Test the solubility: ionic compounds usually dissolve in water but not in hexane.
Test the conductivity: ionic compounds in aqueous solution are good conductors.
Give two examples of molecules that contain a polar bond but are not polar molecules.
Any valid examples.
Give an example of a molecule/ion that has resonance structures. You have to draw the resonance structures correctly!
Any valid drawings of a molecule/ion that can exist realistically.
How do boiling points of different hydrides in Group 14,15,16 and 17 show proof of the existence of intermolecular forces?
Group 14 elements form non-polar hydrides with a tetrahedral shape. The boiling point increases down the group meaning that the London forces become stronger the larger the element.
Group 15, 16 and 17 elements all form polar hydrides with different shapes. The boiling points are higher than those of Group 14 hydrides and increase for Group 15, 16 and 16 as polarity of the bonds increases meaning that the dipole-dipole attractions are stronger.
The first elements in Group 15, 16 and 17, (N, O and F, respectively) form hydrides that can form hydrogen bonds. Their boiling points are the highest as hydrogen bonds are the strongest intermolecular forces and require most energy to be overcome.
Suggest why transition metals have very strong metallic bonds.
A large number of electrons, from both 3d and 4s subshells, can become delocalised.