Eduqas GCSE Chemistry 5 Bonding, Structure and Properties Exam Questions

About Eduqas GCSE Chemistry 5 Bonding, Structure and Properties

Bonding, structure and properties explains why substances behave as they do. In Eduqas GCSE Chemistry you study ionic bonding by electron transfer, covalent bonding by shared pairs and metallic bonding, then link each to structure: giant ionic lattices, simple molecules, giant covalent structures and metals. The carbon allotropes diamond, graphite, graphene and fullerenes are covered, along with nanoparticles and their surface area to volume ratio. The topic builds on electronic structure (topic 2) and supports electrolysis (topic 6) and polymers (topic 10). Examiners regularly ask for dot and cross diagrams and for explanations of melting point, conductivity and hardness that refer to the correct particles and forces.

What you need to know

• Ionic bonding Metal atoms lose electrons and non-metal atoms gain electrons to form ions with full outer shells. Oppositely charged ions are held by strong electrostatic forces in a giant ionic lattice, giving high melting points. Ionic compounds conduct when molten or dissolved because the ions can move.
• Covalent bonding Non-metal atoms share pairs of electrons. Simple molecules such as H2O, CH4, NH3 and CO2 have strong covalent bonds but weak intermolecular forces, so they have low melting and boiling points and do not conduct.
• Giant covalent structures Diamond: each carbon bonded to four others, very hard, very high melting point, no conduction. Graphite: layers of carbons each bonded to three others, with delocalised electrons that let it conduct, and weak forces between layers so it is soft. Silicon dioxide is also giant covalent.
• Graphene and fullerenes Graphene is a single layer of graphite, very strong and an excellent conductor. Fullerenes such as C60 are hollow cages of carbon atoms, and carbon nanotubes are cylindrical fullerenes with high tensile strength.
• Metallic bonding Metals have a lattice of positive ions in a sea of delocalised electrons. They conduct electricity and heat because the electrons move, and are malleable because layers of ions can slide.
• Nanoparticles Nanoparticles are 1 to 100 nm across and have a very high surface area to volume ratio, so they can be very effective catalysts and have different properties from bulk material. They are used in sun creams, cosmetics and medicine, but possible health and environmental risks are not fully understood.

Common mistakes in 5 Bonding, Structure and Properties

• Saying covalent bonds break when a simple molecular substance melts. The weak intermolecular forces are overcome; the covalent bonds stay intact.
• Saying ionic compounds conduct because electrons move. In ionic compounds it is the ions that move, and only when molten or in solution.
• Saying graphite conducts because of free ions. It conducts because each carbon has one delocalised electron that can move through the layers.
• Describing ionic bonding as sharing electrons. Ionic bonding involves transfer of electrons and attraction between ions.
• Drawing a dot and cross diagram for an ion without square brackets and a charge. Show the outer shell, the brackets and the charge, for example [Na]+.

Try three 5 Bonding, Structure and Properties exam-style questions