C3 Flashcards
What’s a metallic bond?
The electrostatic attraction between positively charged metal ions which share a sea of delocalised electrons
What’s an ionic bond?
The electrostatic attraction between two oppositely charged ions
What’s a covalent bond?
A strong bond between atoms that share a pair of electrons
What’s the difference between evaporation and boiling?
Evaporation - happens at any temp, at the surface
Boiling - happens at boiling point, throughout the liquid
When metal atoms react with non-metal atoms, electrons…
are transferred to form ions
Describe ionic compounds
- regular structures (lattice)
- strong electrostatic forces of attraction in all directions between oppositely charged ions
Why do giant ionic compounds have a high melting and boiling point?
Strong electrostatic forces between oppositely charged ions take a lot of energy to break
Why can giant ionic compounds only conduct electricity when molten or in a solution?
When solid, ions are fixed so cannot move to carry a charge, but when molten or in a solution, they are free to move and carry a charge
Why do metals have high melting points?
It takes a lot of energy to break strong metallic bonds
Why can metals conduct heat and electricity?
Electrons are delocalised so are free to move and carry heat or charge
Why are metals malleable and ductile?
Atoms are in layers that can slide over each other
Why are alloys made?
Pure metals are too soft for many uses so are mixed with other metals to make alloys which are harder
what happens when non-metal atoms react with other non-metal atoms?
Electrons are shared to form a covalent bond
What are simple covalent molecules usually?
gases or liquids that have low melting and boiling points
Simple covalent bonds have _____ bonds between atoms but _______
- strong covalent
- weak intermolecular
Why do simple covalent molecules have low melting and boiling points?
weak intermolecular forces mean not much energy is needed to break them
Intermolecular forces ____ with size, so ____- molecules have ___ melting and boiling points
- increase
- larger
- higher
What’s a limitation of a 2D model?
Doesn’t show the shape of the molecule
What’s a limitation of a ball and stick model?
Doesn’t show electrons in bonds
What’s a limitation of a giant structure?
Doesn’t show true number of atoms
what is a giant covalent structure?
Solids with very high melting points, with atoms joined by strong covalent bonds
Describe graphite (5)
- carbon atoms in hexagonal rings
- each carbon atom has 3 strong covalent bonds and 1 delocalised electron
- high melting point
- can conduct electricity
- soft because weak forces let layers slide over each other
Describe diamond (5)
- made of carbon atoms
- 4 strong covalent bonds
- high melting point
- can’t conduct electricity
- very hard - each atom held in place by 4 strong covalent bonds
as the side of a cube decreases by a factor of 10, the surface area to volume ratio…
increases by a factor of 10
Nanoparticles have different properties to same materials in bulk, because of…
their high surface area to volume ratio
describe graphene (4)
- layer of graphite
- can conduct electricity
- used for electronics and composites
- VERY hard
describe fullerene (4)
- a hollow shape made from graphene
- Buckminster fullerene C60 has a spherical shape
- Carbon nanotubes are cylindrical shapes
- Good for nanotechnology, electronics and materials
Why are fullerenes good for nanotechnology?
Conduct heat and electricity
what do dot and cross diagrams show?
- charge of ions
- arrangement of electrons in an atom or ion
- which element the ion has come from (i.e magnesium)
what dont dot and cross diagrams show?
- the structure of the compound
- the size of the ions
