Bonding and Types of Substance (1+2) Flashcards
What are
ions?
charged particles
What are
cations?
positive ions that form when atoms lose electrons
so they have more protons than electrons
What are
anions?
negative ions that form when atoms gain electrons
so they have more electrons than protons
What does an ion name ending in
-ate
mean?
the ion is negative and contains oxygen and at least one other element
What does an ion name ending in
-ide
mean?
the ion is negative and contains only one element
hydroxide is an exception
Define
ionic bond.
the electrostatic attraction between two or more oppositely charged ions
What is the
structure of ionic compounds?
a giant ionic lattice
- the electrostatic attraction between oppositely charged ions results in positive ions being immediately surrounded by negative ions, and negative ions being immediately surrounded by positive ions
- these ions are held together by strong electrosatic forces
- these forces act in all directions to form a giant lattic structure
What are the positives and negatives of
dot and cross diagrams?
(when representing ionic compounds) (1+, 2-)
+useful for showing how ionic compound are formed and where the electrons in the ions come from
-don’t show the structure of the compound
-don’t show the relative sizes of the ions or how they’re arranged
What are the positives and negatives of
3D models?
(when representing ionic compounds) (2+, 1-)
+show the relative sizes of ions
+show the regular pattern of ions
-only let you see the other layer of the compound
What are the positives and negatives of
ball and stick models?
(when representing ionic compounds) (4+, 1-)
+show the regular pattern of ions
+show how the ions are arranged
+show that the lattice extends beyond what is shown in the diagram
+can show the relative sizes of the ions (if drawn to scale)
-suggest that there are gaps between the ions (which there aren’t)
What are some properties of
ionic compounds?
(melting and boiling points, solubility, electrical conductivity)
- high melting and boiling points
- (mostly) dissolve easily in water
- don’t conduct electricity when solid
- do conduct electricity when molten or aqueous
Explain
melting and boiling points
in relation to ionic compounds.
They have high melting and boiling points due to the strong electrostatic attraction between ions. It takes a large amount of energy to overcome this attraction and break the many strong bonds.
Define
electrical current.
the flow of charged particles
this can either be ions or delocalised electrons
Explain
electrical conductivity
in relation to ionic compounds.
Ionic compounds cannot conduct electricity when solid because the ions are all held in fixed positions and cannot move. When the compound is molten or aqueous, the ions are free to move and they can carry electric charge.
Define
covalent bond.
the electrostatic attraction between a shared pair of electrons and the nuclei of the two bonded atoms
What is a
displayed formula?
a two-dimensional representation of a molecule that shows the covalent bonds as single lines between atoms
What are the positives and negatives of
dot and cross diagrams
when representing covalent bonding? (1+, 2-)
+show which atoms the electrons in a covalent bond come from
-don’t show the relative sizes of the atoms
-don’t show how the atoms are arranged in space
What are the positives and negatives of
displayed formulas
when representing covalent bonding? (2+, 3-)
+show what atoms something contains
+shows how they are connected in large molecules
-don’t show the 3D structure of the molecule
-don’t show which atoms the electrons have come from
-don’t show the correct scales of the atoms
What are the positives and negatives of
ball and stick models
when representing covalent bonding? (3+, 4-)
+show the atoms in a molecule
+show how the atoms are arranged in space
+show the bonds as well as the atoms
-get confusing for large molecules that contain lots of atoms
-make it look like there are big gaps between the atoms
-don’t show where the electrons have come from
-sometimes the atoms are not drawn to scale
Define
simple molecule.
a molecule that is made up of only a few atoms joined by covalent bonds
What is the general size of a
simple molecule?
1 x 10^-10 m
Explain
electrical conductivity
in relation to simple molecules.
simple molecules don’t conduct electricity in any state as there are no ions or delocalised electrons so nothing can carry an electrical charge
Explain
melting and boiling points
in relation to simple molecules.
simple molecular substances have low melting and boiling points because although there are very strong covalent bonds between the atoms within molecules, there are very weak intermolecular forces between the molecules
it’s only the weak intermolecular forces that need to be overcome to change the state of a simple molecular substance - not the stronger covalent bonds
so overcoming these weak intermolecular forces doesn’t take much energy
How do melting and boiling points vary for
simple covalent molecules that are increasing in size?
and why?
As molecules get bigger, the strength of the intermolecular forces increases. So, more energy is needed to break them, and the melting and boiling points increase.
What are
polymers?
molecules made up of long chains of covalently bonded carbon atoms
What is one use of the polymer
poly(ethene)?
plastic film for wrapping and packaging
What are the general characteristics of
giant covalent structures?
- type of bonds?
- melting and boiling points?
- conductivity?
- solubility?
- atoms are joined by covalent bonding
- have very high melting and boiling points
- don’t conduct electricity (graphite and graphene are exceptions)
- not soluble in water
What are the specific characteristics of
diamond?
and one use?
- type of atom?
- how many bonds?
- rigidity?
- melting and boiling points?
- conductivity?
- made up completely of carbon atoms
- each carbon atom is bonded to four others
- very rigid
- very high melting and boiling points
- doesn’t conduct electricity
used to strengthen cutting tools (e.g. saw teeth and drill bits)
What are the specific characteristics of
graphite?
and one use?
- type of atom?
- how many bonds?
- softness?
- melting and boiling points?
- conductivity?
- made up completely of carbon atoms
- each carbon atom is bonded to three others
- soft and slippery
- high melting and boiling points
- can conduct electricity
used as a lubricating material
Why is
graphite a good lubricant?
Graphite is composed of sheets of carbon atoms arranged in hexagons. There aren’t any covalent bonds between the layers - they’re held together by intermolecular forces, so are free to move over eachother.
What are the specific characteristics of
graphene?
and one use?
- type of atom?
- how many bonds?
- strength?
- melting and boiling points?
- conductivity?
- made up completely of carbon atoms
- each carbon atom is bonded to three others
- very strong and lightweight
- high melting and boiling points
- can conduct electricity
can be added to composite materials to improve their strength, can be used in electronics
Tell me about
buckminsterfullerene.
- molecular formula?
- form?
- stability?
- appearance?
- conductivity?
- has the molecular formula of C60
- forms a hollow sphere containing 20 hexagons and 12 pentagons
- stable giant covalent molecule
- forms soft brown-black crystals
- semi-conductor
Tell me about
nanotubes.
- form?
- size?
- conductivity?
- a type of fullerene which are tiny carbon cylinders
- high length to diameter ratio
- good conductor (of both heat and electricity)
What are three uses of
fullerenes?
- medicine
- as catalysts
- strengthening materials
How can fullerenes be used in
medicine?
They can be used to ‘cage’ other molecules by forming around another atom or molecule, which is then trapped inside.
This could be used to deliver a drug to where it is needed
How can fullerenes be used as
catalysts?
They have a huge surface area so they could help make great industry catalysts.
Individual catalyst molecules could be attached to the fullerenes
What does it mean to have
high tensile strength?
the object does not break when stretched
How can fullerenes be used for
strengthening materials?
they have high tensile strength so can be used to strengthen materials without adding much weight
e.g. can be used to strengthen sports equipment that needs to be strong but also lightweight, such as tennis raquet frames
What is the
structure of metals?
It is a giant structure of positive metal ions arranged in a regular pattern. The ions are closely packed. The delocalised electrons form a sea around the ions and are free to move throughout the structure.
There are strong forces of electrostatic attraction between the ions and the electrons. These forces hold the metal structure together.
Define
metallic bonding.
the electrostatic forces of attraction between positive metal ions and negative electrons
Explain
melting and boiling points
in relation to metals.
Metals have high melting and boiling points as the electrostatic forces between the metal ions and the delocalised sea of electrons are very strong, so need lots of energy to be broken.
This means that they’re generally shiny solids at room temperature.
Explain
conductivity
in relation to metals.
Metals can conduct as they have delocalised electrons that are free to move through the whole structure. This also means that they are much better conductors of thermal energy and electricity than most non-metals.
Electrons carry the current or the thermal energy through the structure.
Explain
malleability
in relation to metals.
Metals are malleable as the layers of metal atoms are able to slide over each other.
This means that they can be hammered or rolled into flat sheets
Explain
density
in relation to metals.
Metals generally have a higher density than non-metals. This is because the ions in the metallic structure are packed close together and there aren’t many gaps in the structure as in non-metals.
