Structure And Bonding Flashcards
What is an atom?
The smallest piece of an element that can still be recognised as that element
What is a molecule?
2 or more atoms covalently bonded together. Contain a fixed number of atoms.
What are ionic bonds?
The electrostatic attraction between oppositely charged ions.
Why do giant ionic lattices have high melting and boiling points
Because the electrostatic attraction between oppositely charged ions is very strong, and require a lot of energy to overcome the strong attraction.
Why can ionic compounds not conduct electricity when solid but do when molten and in aqueous solution?
Because in solution or molten, the ions are free to move, and can carry around the charge.
How is a covalent bond formed?
formed between atoms by the sharing of a pair of electrons
What is a covalent bond?
The electrostatic attraction between two nuclei and a shared pair of electrons
Why are substances with a simple molecular structure gases or liquids or solids with low melting and boiling points (in terms of weak intermolecular forces)?
As a result of weak intermolecular forces, the melting and boiling points are very low because the molecules are easily separated.
Why do the melting and boiling point of substances with simple molecular structures increase with relative molecular mass?
Because there are more points along the larger molecules for intermolecular forces to act between then, so more energy is needed to break the forces.
Why are substances with giant covalent structures solids with high melting and boiling points?
Because all atoms are bonded together by strong covalent bonds, so it takes a lot of energy to break them.
Do covalent compounds conduct electricity, and why?
No, because the molecules don’t have any overall electrical charge and all the electrons are held tightly in the atoms or in covalent bonds and so are not able to move from molecule to molecule.
How does the structure of diamond influence its physical properties?
1) Diamond is made up of a network of carbon atoms that each form four covalent bonds
2) the strong covalent bonds take lots of energy to break, so diamonds has a high melting point.
3) the strong covalent bonds hold the atoms in a very rigid lattice structure, so it’s really hard.
4) it doesn’t conduct electricity because it has no free electrons or ions.
How does the structure of graphite influence its physical properties?
1) In graphite, each carbon atom only forms three covalent bonds, creating layers of carbon atoms.
- The layers are only held together weakly by intermolecular forces, so are free to Slide Over each other.
- This makes graphite soft and slippery.
2) Graphite’s got a high melting point - the covalent bonds in the layers need lots of energy to break.
3) Only three out of each carbon’s four outer electrons are used in bonds, so each carbon atom has one electron that’s delocalised and can move. So graphite is a non-metal that conducts electricity.
How does the structure of C60 fullerene influence its physical properties?
1) C60 fullerene molecules are hollow spheres made up of 60 carbon atoms.
2) Unlike diamond and graphite, C60 isn’t a giant covalent structure, but just made up of large covalent molecules.
3) The C60 molecules are only held together by intermolecular forces and so they can Slide Over each other, meaning the material is soft.
4) Like graphite, each carbon in C60 fullerene has one delocalised electron. However, the electrons can’t move between the molecules, C60 fullerene is a poor conductor or electricity.
What is diamond used for?
Jewellery
Industrial drills
