C2: Bonding Flashcards
How do metal atoms bond to each other?
-Metallic bonding
-Form a lattice of positive ions
-Surrounded by a ‘sea’ of delocalised electrons
Why do metals make good conductors?
Electrons are free to move
How do metals bond to non-metals?
-Ionic bonding
-Metal atoms donate electrons to non-metals to form ions
How do we show the electrons on the outer shells in ionic bonding?
-Dot and cross diagrams
-Metals always end up with an empty outer shell
Non-metals always end up with a full outer shell
What must the charges of all ions in an ionic compound add up to?
Zero
How are ions arranged?
-In a lattice of repeating units of positive and negative ions
-These form a crystal
What are characteristics or ionic substances?
-High melting/boiling points
-Due to strong ionic bonds
-Ions have strong electrostatic forces between them
Can ionic structures conduct electricity?
-Yes, when molten or in a solution (dissolved)
-Ions are free to move in these states so can carry charge
What are examples of molecular ions?
-Hydroxide ions: OH-
-Sulphate ions: SO2-
-Carbonate ions: CO2-
-Nitrate ions: NO-
-Ammonium ions: NH+
What is a molecular ion?
A particle made of one or more atom with an overall positive or negative charge
What can ionic compounds also be called?
Salts e.g. sodium chloride
What are positive ions also know as?
Cations
What are negative ions also known as?
Anions
How do non-metals bond to each other?
By covalent bonding
What is covalent bonding?
-Atoms share electrons to gain full outer shells
-Every covalent bond consists of a pair of shared electrons
What does the dot & cross diagram look like for covalent bonding?
Dots and crosses in the middle of the overlapping atoms
What determines the number of bonds an atom makes?
The number of electrons an atom needs
What are simple covalent structures?
Molecules with a small number of atoms covalently bonded
What are characteristics of covalently bonded molecules?
-Low melting/boiling points
-Due to weak intermolecular forces
-Take little energy to overcome
What are giant covalent structures?
Structures that consist of repeating units of atoms to make what are essentially giant molecules
What are examples of giant covalent structures?
-Diamond
-Silicon dioxide (‘silica’)
-Graphite
What are properties of diamond?
-Very hard
-Strong bonds
-Very high melting and boiling points
Where are properties of graphite?
-Soft and slippery (layers can slide past each other)
-Due to weak bonds between layers
-Can conduct electricity
-Due to delocalised electrons
What are alloys?
Mixtures of metals
What are properties of metal alloys?
-Strong
-Layers cannot slide over each other easily
-Due to different sized atoms disrupting the layers
What is graphene?
A single layer of graphite
What can fullerenes/nanotubes be used for?
-Electronics
-Composites
-Medical purposes
What is a spherical fullerene?
Buckminster fullerene (60 carbons)
How big are nano particles?
100-2500nm
How big are coarse particles e.g. dust?
> 2500nm
What happens when to the surface to volume ratio when the length of the side of a cube doubles?
It is halved
Why are fullerenes useful?
They have a high surface to volume ratio
