Structure and Bonding A level chem confused (urgent)

in the spec it says:
The four types of crystal structure:
• ionic
• metallic
• macromolecular (giant covalent)
• molecular.
The structures of the following crystals as examples of
these four types of crystal structure:
• diamond
• graphite
• ice
• iodine
• magnesium
• sodium chloride.

Firstly, I don't understand how a molecular is a type of crystal structure as I thought crystal structure are giant structures that re very strong. And secondly, I don't understand what Ice is an example of. is it an example of molecular?

Thank you very much its cuz i hv a test on Monday and im lowkey really scared cuz im unconfident with identifying structures and bonding in particular examples

Macromolecular structures involve diamond where each atom is bonded to 4 others. Whereas molecular (aka simple molecular) is just separate molecules held together in a solid state by intermolecular forces (ie. van der Waals, hydrogen bonds, dipole-dipole). An example of molecular is iodine: the diatomic iodine molecules are held together by van der Waals.

Ice is technically molecular but has a structure similar to macromolecular due to the hydrogen bonds that hold the water molecules in place. The water
molecules are arranged like a macromolecular crystal but aren't actually one, if you know what I mean...

Hope that helps!

in the spec it says:
The four types of crystal structure:
• ionic
• metallic
• macromolecular (giant covalent)
• molecular.
The structures of the following crystals as examples of
these four types of crystal structure:
• diamond
• graphite
• ice
• iodine
• magnesium
• sodium chloride.

Firstly, I don't understand how a molecular is a type of crystal structure as I thought crystal structure are giant structures that re very strong. And secondly, I don't understand what Ice is an example of. is it an example of molecular?

Thank you very much its cuz i hv a test on Monday and im lowkey really scared cuz im unconfident with identifying structures and bonding in particular examples

All this content clicked for me once I'd made a massive A3 mindmap comparing the types of bonding - I found that colour coding helped spruce it up a little, not too sure if that'll work for you too. Be sure to compare relative bond strengths, species bonding etc.

Work through practice questions. It'll all fall into place soon enough, though aim to get to grips with the content before moving onto new stuff. Have a look into the ~18 phases of ice and polymorphism if you want -- this is linked to that white sheen (bloom) you can find on slightly older bars of chocolate, fun fact.

Last but not least, have more confidence! You can do this!


Also, dependent on which specification you're with, you may need to avoid the use of "van der Waals". It's a good habit to get into too for further studies. You may have heard of "London forces"?? Then again, your spec might be totally unfazed by the use of vdW!

Crystal structures/crystal types just refers to the variety of structures molecules/compounds may have - it doesn't necessarily mean they are strong. Simple molecular substances such as diatomic iodine have covalent bonds but very weak induced dipole dipole interactions between molecules which means very little energy is required to break the forces of attraction between molecules.

Diamond and graphite would be an example of giant covalent/macromolecular.
Iodine is simple molecular.
Magnesium is metallic.
Sodium chloride is ionic.

Water is one of those weird substances, it doesn't always follow the rules - obviously strong hydrogen bonds are formed between the oxygen on one water molecule and the hydrogen on another. The oxygen molecule has the lone pair of electrons, so the hydrogen is strongly attracted due to the electronegativity on the oxygen. Ice is just the solid form of liquid water, so it is still classed as a simple molecular structure - there are very strong covalent bonds formed within each water molecule but the induced dipole dipole and hydrogen bonds formed between water molecules are weaker and don't require a lot of energy to break.

Macromolecular structures involve diamond where each atom is bonded to 4 others. Whereas molecular (aka simple molecular) is just separate molecules held together in a solid state by intermolecular forces (ie. van der Waals, hydrogen bonds, dipole-dipole). An example of molecular is iodine: the diatomic iodine molecules are held together by van der Waals.

Ice is technically molecular but has a structure similar to macromolecular due to the hydrogen bonds that hold the water molecules in place. The water
molecules are arranged like a macromolecular crystal but aren't actually one, if you know what I mean...

Hope that helps!