Loading subjects
Bonding, Structure & Energy · Part 1 of 3
21 exam-style questions with model answers, plus 28 quick multi-choice questions — every question on this part of the standard, grouped by the 7 pages of notes they come from.
Write a full answer before you reveal the model one. That comparison is where the learning happens.
Give the formula of the ionic compound formed between magnesium and chlorine, and state the charge on each ion.
Explain how the ionic bond in sodium oxide (Na2O) forms, referring to electron transfer and the resulting attraction.
A student says: 'In magnesium oxide, each magnesium ion is bonded to one oxide ion, so MgO is a molecule with one ionic bond.' Evaluate this statement and give a fully correct account of the bonding and structure of magnesium oxide.
Define a covalent bond and state how many electrons are in one single bond.
Explain why oxygen atoms form a double bond in O2 but chlorine atoms form only a single bond in Cl2.
Nitrogen gas (N2) is very unreactive and is used to fill food packaging, while oxygen (O2) reacts readily. Explain this difference in terms of the bonding in each molecule, and comment on what this shows about the relationship between bond order and bond strength.
Describe metallic bonding.
Explain why metals conduct electricity in the solid state, whereas ionic compounds do not.
Compare the bonding in magnesium and in magnesium chloride, and use the comparison to explain why magnesium can be hammered into a sheet while magnesium chloride shatters when struck.
State how many bonding pairs and lone pairs are around the oxygen atom in a water molecule.
Draw the Lewis structure of carbon dioxide (CO2) and explain why the molecule contains double bonds rather than single bonds.
A student draws the Lewis structure of methane with carbon in the centre, four C–H bonds and one lone pair on the carbon. Evaluate the structure, identify the error and its cause, and give the correct structure. Then explain how the same checking method would confirm a correct structure for hydrogen cyanide, HCN.
State the shape and bond angle of a methane molecule, CH4.
Explain why ammonia (NH3) is pyramidal with a bond angle of 107°, while methane (CH4) is tetrahedral with 109.5°.
Compare the shapes and bond angles of CH4, NH3 and H2O, explaining the trend. Then explain why CO2, which also has two atoms bonded to a central atom, is linear rather than bent like H2O.
Explain what makes a covalent bond polar.
Carbon dioxide contains polar bonds but is a non-polar molecule. Explain why.
CH4 and CHCl3 are both tetrahedral, yet one is polar and one is not. Explain this difference fully, and use your reasoning to predict whether CH2Cl2 is polar.
State what is overcome when a molecular substance such as iodine melts.
Explain why molecular substances generally have much lower melting points than ionic substances.
Water (M = 18) boils at 100 °C while methane (M = 16) boils at −162 °C, despite having almost the same molar mass. Explain this difference fully, and explain why the boiling of water is a physical change rather than a chemical one.