Bonding, Structure and Properties of Matter Flashcards
Ion
Charged particle formed when an atom/molecule loses/gains electrons to get a full outer shell
What happens when metals form ions
- lose electrons
- form positive ions
What happens when non-metals form ions
- gain electrons
- form negative ions
How is charge of an ion determined
number of an electrons lost
Most likely groups to form ions
- group 1
- group 2
- group 6
- group 7
Types of bonds
- ionic
- covalent
- metallic
ionic bond
Strong attraction between oppositely charged ions by electrostatic forces, caused by metals and non-metals reacting together
What happens in an ionic bond
- metal atom loses electrons
- electrons transferred to non-metal
What diagram shows ionic bonds
Dot and cross
Limitations of dot and cross diagram
Doesn’t show 3 dimensional nature of structure
Structure of ionic compound
Giant ionic lattice
Structure of giant ionic lattice
- ions form closely packed regular lattice arrangement
- strong electrostatic forces of attraction between oppositely charged particles in all directions in lattice
Properties of ionic compounds
- high melting points
- high boiling points
Why do ionic compounds have high melting/boiling points
There are strong electrostatic forces of attraction between ions that take a lot of energy to overcome
When can ionic compounds conduct electricity
When molten
Molten
Metled
Why can ionic compounds conduct electricity when molten
Ions are free to move and carry a charge
When can’t ionic compounds conduct electricity
When solid
Why can’t ionic compounds conduct electricity when solid
ions held in place so can’t carry a charge
What happens to some ionic compounds in water
- they dissolve
- ions separate and are free to move in solution
- carry electric charge and conduct electricity
Empirical formula
- what atoms are in an ionic compound
- includes number of each atom
Covalent bond
- bond between non-metals
- electrons shared to get full outer shells
- positive nuclei attracted to shared electrons through electrostatic forces
Diagram to show covalent bonds
Dot and cross
Simple molecular substances
Substances made up of molecules containing a few atoms joined together by covalent bonds
Properties of simple molecular substances
- atoms within molecules held together by very strong covalent bonds
- forces of attraction between molecules very weak
- low melting/boiling points
- usually gas/liquid at room temperature
- melting/boiling points increase as molecules get bigger
- don’t conduct electricity
Why do simple molecular structures have low melting/boiling points
To melt/boil, only have to break weak intermolecular forces (easy to do)
Why do melting/boiling points of simple molecular substances increase as they get bigger
- strength of intermolecular forces increases
- more energy needed to break them
Why can’t simple molecular structures conduct electricity
Not charged so there are no free electrons to carry a charge
Polymers
Long chains of repeating small units, forming a long molecule that has repeating sections
How are atoms in polymers linked
Strong covalent bonds
How are polymers drawn
- repeating section in brackets
- ‘n’ outside brackets showing number of sections
State of polymers at room temperature
Solid
Why are polymers solid at room temperature
Stronger intermolecular forces, requiring more energy to break them
What type of molecule are giant covalent structures
Macromolecules
Properties of giant covalent structures
- all atoms bonded to each other by strong covalent bonds
- high melting/boiling points
- usually can’t conduct electricity
Why do giant covalent structures have high melting/boiling points
Lots of energy needed to break covalent bonds between atoms
Why don’t giant covalent structures usually conduct electricity
Don’t contain charged particles
Examples of giant covalent structures
- diamond
- graphite
- silicon dioxide
Allotrope
Different structural forms of the same element in the same physical state
Allotropes of carbon
- diamond
- graphite
- fullerene
Properties of diamond
- very hard
- high melting point
- doesn’t conduct electricity
Why is diamond very hard
Each carbon atom forms 4 covalent bonds
Why does diamond have a high melting point
Covalent bonds are strong and need a lot of energy to break
Why doesn’t diamond conduct electricity
No free electrons/ions to carry a charge
Properties of graphite
- each carbon atom forms 3 covalent bonds, creating sheets of carbon atoms arranged in hexagons
- layers held together weakly (no covalent bonds) so it is soft and slippery - good lubrication
- high melting point
- conducts electricity + thermal energy
Why does graphite have a high melting point
Covalent bonds require much energy to break
Why does graphite conduct electricity and thermal energy
Only 3 of carbons electron used in bonds - 1 electron delocalised and free to move
Graphene
- 1 layer of graphite
- sheet of carbon atoms joined together in hexagons
- 1 atom thick
- contains delocalised electrons to conduct electricity
Fullerene
- molecules of carbon shaped liked closed tubes or hollow balls
- made up of carbon atoms arranged in hexagon sometimes containing pentagons (rings of 5 carbon atoms) or heptagons (rings of 7 carbon atoms)
- can form nanotubes
Uses of fullerene
- delivering a drug into body - fullerene structure forms around other atoms/molecules and traps them inside
- industrial catalyst - large surface area, individual catalyst molecules could be attached to fullernes
- lubrication
First fullerene to be discovered
Buckminsterfullerene
Molecular formula of Buckminsterfullerene
C₆₀
What does Buckminsterfullerene form
Hollow tubes
Nanotubes
Tiny carbon cylinders
Properties of nanotubes
- high ration between length and diameter
- conduct electricity + thermal energy
- high tensile strength so don’t break when stretched
nanotechnology
Technology that uses very small particles like nanotubes
Uses of nanotubes
- strengthening materials without adding much weight
- used in electronics
Metallic bonding
Strong electrostatic forces of attraction between positive metal ions and shared negative electrons, holding atoms together in a regular struture
Properties of metals
- mostly solid at room temperature - high melting/boiling points
- good conductors of electricity
- good conductors of heat
- malleable
- strong and hard to break
Why are most metals solid at room temperature
electrostatic forces between metal atoms and sea of delocalised electrons need lots of energy to be broken to melt/boil
Why are metals good conductors of electricity/heat
delocalised electrons carry electrical charge + thermal energy through whole structure
Why are metals malleable
Layers of atoms can slide over each other
Why aren’t metals always right for certain jobs
Often too soft when pure
How to deal with metals being too soft for certain jobs
Mix them with other metals to make them harder
Alloy
Mixture of 2 or more metals or a metal and another element
Why are alloys harder than pure metals
- different metals have different sized atoms
- when another element is mixed with a pure metal, new metal atoms will distort layers of metal atoms, making it more difficult fore layers to slide over each other
What determines what state something is a certain temperature
Strength of forces of attraction between particles of the material
What determines strength of forces of attraction between particles in a material
- material - structure of substance + types of bonds holding particles together
- temperature
- pressure
Criticisms of the particle theory model
- uses inelastic/spherical particles instead of atoms/ions/molecules
- doesn’t show forces between particles so can’t see how strong they are
Aqueous
dissolved in water
What happens when a solid is heated
- particles gain more energy and vibrate more, this weakens the forces holding the solid together
- at certain temperature (melting point), particles have enough energy to break free from their positions (melting) and turn into a liquid
What happens when a liquid is heated
- particles gain more energy and move faster
- bonds holding liquid together weaken and break
- at certain temperature (boiling point), particles have enough energy to break bonds (boiling) and turn into a gas
What happens when gases cool
- particles no longer have enough energy to overcome forces of attraction between them
- bonds form between particles
- as boiling point, so many bonds have formed between gas particles, it has condensed and become a liquid
What happens when liquids cool
- particles have less energy so move around less
- not enough energy to overcome forces of attraction between particles so bonds form between them
- at melting point, so many bonds have formed between particles, they’re held in place
- liquid had frozen to become a solid
What determines amount of energy needed for a substance to change state
How strong forces between particles are