C3-Structure And Bonding Flashcards
Which states of matter can flow?
Liquids and gases
Which states of matter are considered fluids?
Liquids and gases
What is the change of state called by which a solid changes directly to a gas without melting?
Sublimation
What are the limitations of the particle model?
-The particles aren’t solid (most of an atom is empty space)
-The particles aren’t spheres
-It doesn’t show the forces between particles so there is no way of showing how strong they are
Define a compound
A compound contains two or more elements that are are chemically combined
What holds ions together in ionic compounds?
Very strong electrostatic forces of attraction
Why do ionic compounds have high melting and boiling points?
To seperate the ions you have to overcome all the strong electrostatic forces of attraction acting in all directions
Why can’t a solid ionic compound conduct electricity?
Its ions are held in fixed positions in the lattice so it cannot carry the electrical charge
What are the two ways to make the ions in an ionic compound mobile?
-Melting the compound
-Dissolving the compound in water
What is covalent bonding?
Where atoms of non-metals share electrons with each other
What is ionic bonding?
Where a metal gives its electrons to a non-metal
Limitations of the 2D ball and stick model
Does not show the true shape of the molecule (shows the bonds at 90 degrees)
Limitations of the dot and cross model
-Shows electrons to be different whereas in reality all electrons are the same
-The electrons are in fixed positions but scientists believe that the electrons in covalent bonds are constantly moving
Why do simple molecules have low melting and boiling points?
There are weak intermolecular forces of attraction between molecules
Why can’t simple molecules conduct electricity?
They aren’t charged so there ae no free electrons or ions
What are simple molecular substances made up of?
A few atoms joined together by covalent bonds
Give examples of some common simple molecular substances
-H2
-Cl2
-O2
-N2
-CH4
-H2O
-HCl
What are giant covalent structures made up of?
Lots of atoms, all bonded to each other by strong covalent bonds
Name 3 properties of giant covalent structures
-Very high melting and boiling points
-Insoluble in water
-Apart from graphite, they are hard and do not conduct electricity
Why do giant covalent structures have high melting and boiling points?
Lots of energy is needed to break the covalent bonds between the atoms
Give 3 examples of giant covalent structures
-Diamond
-Graphite
-Silicon dioxide
Explain the bonding in diamond
Each carbon atom forms four covalent bonds in a very rigid giant covalent structure
Explain the bonding in graphite
Each carbon atom forms three covalent bonds to create layers of hexagons. Each carbon atom also has one delocalised electron
Why can the layers in graphite slide over each other easily?
There are no covalent bonds between the layers, only weak intermolecular forces
Why can graphite conduct electricity and thermal energy?
Only three of its four electrons are used in bonding so one electron is free to move along the layers
What is graphene?
A single sheet of carbon atoms from graphite
Why is graphene considered a 2D substance?
It is just one atom thick
Properties of graphene
-Excellent conductor of electricity and thermal energy
-Very strong
-Very low density
What are fullerenes?
Molecules of carbon shaped like closed tubes or hollow balls
