Bonding Structure And Matter Flashcards
What is ionic bonding?
Ionic bonding is the electrostatic attraction between positive and negative ions.
It is a relatively strong attraction.
How are ionic compounds held together? (3)
● They are held together in a giant lattice.
● It’s a regular structure that extends in all directions in a substance.
● Electrostatic attraction between positive and negative ions holds the structure together.
State properties of ionic substances (3)
● High melting and boiling point (strong electrostatic forces between oppositely charged ions)
● Do not conduct electricity when solid (ions in fixed positions).
● Conduct when molten or dissolved in water - ions are free to move.
How are ionic compounds formed? Explain in terms of MgO
Reaction of a metal with a non-metal.
Electron transfer occurs - metal gives away its outer shell electrons to non-metal.
Mg is in Group II, so has 2 available outer shell electrons. O is in Group VI, so can accept 2 electrons to get a full outer shell
configuration.
Mg becomes Mg2+ and O becomes O2− (oxide).
They become electrostatically attracted to one another (opposites attract) and form an ionic compound.
In this case (MgO) magnesium oxide.
What is a covalent bond?
Covalent bond is a shared pair of electrons between two or more atoms.
Describe the structure and properties of simple molecular covalent substances (4)
- Do not conduct electricity (no ions)
- Small molecules
- Weak intermolecular forces, therefore:
- Low melting and boiling points
How do intermolecular forces change as the mass/size of the molecule increases?
They increase. That causes melting/boiling points to increase as well (more energy needed to overcome these forces).
What are polymers?
What are thermosoftening polymers?
Polymers are very large molecules with atoms linked by covalent bonds.
Thermosoftening polymers melt/soften when heated.
There are no bonds between the polymer chains.
Strong intermolecular forces ensure that the structure is solid at room temperature. These forces are overcome with heating - polymer melts
Name factors (3) of and give examples (3) of giant covalent substances
- Solids, atoms covalently bonded together in a giant lattice.
- High melting/boiling points – strong covalent bonds.
- Mostly don’t conduct electricity (no delocalised e−)
- Diamond, graphite, silicon dioxide.
Name the 5 allotropes of carbon
Diamond
Graphite
Graphene
Fullerene
Nanotubes
Describe the structure and properties of diamond (4)
– four, strong covalent bonds for each carbon atom
– very hard (Strong bonds)
– very high melting point (strong bonds)
– does not conduct (no delocalised electrons)
Used in cutting tools and drill tips
Describe the structure and properties of graphite (5)
– three covalent bonds for each carbon atom
– layers of hexagonal rings
– high melting point
– layers free to slide as weak intermolecular forces
between layers; soft, can be used as a lubricant
– conduct thermal and electricity due to one delocalised
electron per each carbon atom
Used in pencil lead, as a lubircant and as an electrode (electrolysis)
Describe the structure and properties of graphene (1)
A single layer of graphite
Describe the structure and properties of fullerenes (3)
– hollow shaped molecules
– based on hexagonal rings
– C60 has spherical shape, simple
molecular structure (Buckminsterfullerene)
Describe the structure and properties of nanotubes (3)
- A cylindrical fullerene
- High tensile strength (strong bonds)
- Conductivity (deloc. electrons)
What is metallic bonding?
Forces of attraction between delocalised electrons and nuclei of metal ions.
Describe properties of metals (3)
-High melting/boiling points (strong forces of attraction)
- Good conductors of heat and electricity (delocalised electrons)
- Malleable, soft (layers of atoms can slide over each other whilst maintaining the attraction forces)
What are alloys and why are they harder than pure metals?
Alloys:
- mixtures of metal with other elements, usually metals
- different sizes of atoms distorts the layers, so they can’t slide over each other, therefore alloys are harder than pure metals
What are the limitations of the simple model?
There are no forces between spheres and atoms, molecules and ions are solid spheres – this is not true
A pure substance /mixture will melt or boil at…?
Pure: a fixed temperature.
Mixture: over a range of temperatures.
What is nanoscience?
Science that studies particles that are 1 - 100nm in size
State the uses of nanoparticles
- Medicine (drug delivery systems)
- Electronics
- Deodorants
- Sun creams (better skin coverage and more effective protection
against cell damage)
Nanoparticles have a high…
Surfacr area to volume ratio
Pros (1) and cons (3) of dot and cross diagrams
Pros :
Show how ionic compounds are formed
Cons :
Don’t show the structure of compound, size of ions or ion arrangement
Pros (2) and cons (1) of 3D Models
Pros :
Shows the relative sizes and regular patterns or ions
Cons :
Only lets you see the outer layer of the compound
Pros (3) and cons (1) of Ball and Stick model
Pros :
Show the regular pattern and arrangement in an ionic lattice
May show relative sizes
Suggest that the crystals extend beyond what is shown
Cons :
Suggest there are gaps between the ions
List 5 ways in which fullerenes are used
In medicine
(They can deliver or cage drugs)
As catalysts
(Large surface area, industrial catalysts)
As lubricants
(Reduce friction)
In strengthening materials
(They don’t break when stretched)
In electronics
(Small and can conduct electricity)
Order the size of nano, coarse and fine particles
Coarse -> Fine -> Nano
What is the diameter of a nanoparticle
1nm to 100nm
Name the 4 uses of nanoparticles
Good catalysts
Nanomedicine
Electronics
(Thin light display screens or tiny memory chips)
Cosmetics, sun cream, deodorant
(Some nanoparticles have anti bacterial properties) + (they may help protect against UV rays)
