Structure and Bonding Flashcards
What are ions?
Charged particles than can be single atoms (Cl^-) or groups of atoms (NO3^-)
Which groups of elements readily/easily form ions?
Groups 1,2,6 and 7
How do groups 1 and 2 form ions?
Metals, lose electrons to form positive ions (cations)
How do groups 6 and 7 form ions?
Non-metals, gain electrons to form negative ions (anions)
What does it mean if elements are all in the same group?
They have the same number of outer electrons, form ions with the same charges
What is ionic bonding?
When a metal and a non metal react together.
- metal loses electrons (+ve)
- non-metal gains these electrons (-ve)
- strong electrostatic forces
- oppositely charged ions
What is an ionic compound?
- Structure of a giant ionic lattice
- made up of ions
What is a giant ionic lattice?
- closely packed lattice arrangement- structure
- strong electrostatic forces between oppositely charged ions
What are properties of ionic compounds?
- High melting and boiling points (strong electrostatic bonds), needs lots of energy to overcome
- Solid= fixed position, can’t conduct electricity
Melted= free to move, carry electrical charge - Some dissolve in water-> ions free to move, carry electrical charge
What are covalent bonds?
When non-metal atoms bond together, sharing a pair of electrons
- electrostatic forces, strong
- in non-metal elements and compounds
What are simple molecular substances made up of?
Made up of molecules containing a few atoms joined by covalent bonds
What are some examples of simple molecular substances?
- Hydrogen
- Chlorine
- Oxygen
- Nitrogen
- Methane
- Water
- Hydrochloric acid (Hydrogen Chloride)
What are properties of simple molecular substances?
- Simple molecular structures
- Strong covalent bond, weak intermolecular forces
- Low Melting and Boiling point (to melt you only need to break the weak intermolecular forces)
- Most are gas or liquid at room temp
- as molecules get bigger, strength of intermolecular forces increases, more energy needed -> Melting and Boiling point increases
- No charge, don’t usually conduct electricity
What are Polymers?
- lots of small units linked by strong covalent bonds to form a long molecule
- More energy needed to break them -> intermolecular forces are larger in simple covalent molecules
- lower boiling points than ionic or giant molecular structures (weak intermolecular forces)
What are Giant covalent structure features+ examples?
- High melting and boiling points (strong covalent bonds)
- Don’t conduct as solid or molten (apart from exceptions like graphite etc)
- Diamond, Graphite, Silicon dioxide (silica)
- Macromolecules
What are the features of Diamond?
- Each carbon forms 4 covalent bonds, Very rigid structure
- High melting point, strong covalent bonds
- Doesn’t conduct electricity
- Carbon allotrope
What is Graphite ?
- forms 3 covalent bonds, creates layers of hexagons
- No bonds between layers, free to more over each other-> soft slippery
- ideal as a lubricant
- high melting point (covalent bonds in the layers)
- 1 delocalised electron per atom, conducts electricity and thermal energy
What are the features of the structure of Silicon Dioxide (silica)?
- Silicon and Oxygen
- What sand is made of
What is an allotrope?
Different structural forms of the same physical element in the same physical state
What is graphene?
- a single layer of graphite
- sheet of carbon atoms joined in hexagons
- 1 atom thick
- strong (covalent bonds, light -> can be added to materials to improve strength without adding much weight
- delocalised electrons, conduct electricity-> can be used in electronics
What are Fullerenes?
Molecules of carbon, shaped like hollow balls or small tubes
- Can be arranged as hexagons, pentagons or heptagons (rings of carbon atoms)
- Cage other molecules-> deliver drugs into the body
- Huge SA-> industrial catalysts, lubricants
What is the Buckminsterfullerene?
- First fullerene to be discovered
- C60
- Forms hollow sphere
What are nanotubes?
Tiny carbon cylinders, formed from fullerenes
- can conduct electricity and thermal energy
- high tensile strength (don’t break when stretched)
- nanotechnology-> used in electronics, strengthen materials without adding weight (tennis racket frames)
What is metallic bonding?
Strong electrostatic attraction between positive metal ions and delocalised electrons
- strong
- metallic elements, alloys
- delocalised electrons produce properties of metal
- high melting point (strong electrostatic forces)
- Solid at room temp
- good conductors of electricity and heat (delocalised electrons)
- Malleable (bent, hammered, rolled into sheets) ,layers of metal can slide over each other
What is the difference between Alloys and pure metals?
Pure metals-> too soft, mixed with other metals to make them harder
Alloys-> harder, more useful
- Different metals have different sized atoms, distorting layers making it harder for them to slide over, making the material harder
What is an Alloy?
a mixture of 2 or more metals or a metal and another element
What determines what state a substance will be at a certain temperature?
The strength of the forces of attraction
What does the strength of the forces of attraction depend on?
-Material (structure + bonds)
-Temperature
-Pressure
How do particles behave in a solid?
- strong forces of attraction
- close together, fixed positions
- regular lattice arrangement
- definitive shape and volume
- vibrate in fixed position, hotter= more vibration (solids expand)
How do particles behave in a liquid?
- Weak forces of attraction
- Randomly arranged, free to move past each other (tend to stick closer together)
- Definitive volume NOT shape
- Constantly moving in random motion, hotter= more faster movement (liquid expands)
How do particles behave in a gas?
- Very weak forces of attraction
- Free to move, far apart, travel in straight lines
- NO definitive shape OR volume
- Constantly moving in random motion, hotter= faster movement (gasses expand or pressure increases)
What is Melting?
The change of state from a solid to a liquid
- solid is heated, gains more energy
-particles vibrate move, weakens the forces - melting point, enough energy, particles break free, turns to liquid
What is Boiling?
The change of state from a liquid to a gas
- Liquid is heated, particles gain more energy
- Particles move faster, weakens + breaks bonds
- Boiling point, enough energy to break bonds, becomes gas
What does the amount of energy needed to change state depend on?
How strong the forces between particles are
- the stronger the forces, the more energy that is needed, the higher the melting + boiling temps
What is Condensing?
The change of state from a gas to a liquid
- gas cools, particles dont have enough energy to overcome forces of attraction
- bonds form
- boiling point, so many bonds have formed, gas becomes liquid, Condensing
What is freezing?
The change of state from a liquid to a solid
- Liquid cools, particles have less energy
- not enough energy to overcome attraction, more bonds form
-melting point, so many bonds form, particles held in place, become solid, Freezing.
What are Nanoparticles?
Diameter between 1nm and 100nm
- only contain a few 100 atoms
What is nanoscience?
Science that investigates the uses and properties of nanoparticles
What is the relationship between SA and Volume in Nanoparticles?
As the particles decrease in size (volume decreases), SA increases in relation to volume
SA:V ratio -> increases
- less of a nanoparticle to work as an effective catalyst compared to products with billions of atoms rather than hundreds
What are uses of Nanoparticles?
- Catalysts -> large SA:V ratio
- Nanomedicine -> fullerenes deliver drugs
- Electrical circuits in computer chips -> conduct electricity
- Cosmetics-> improve moisturiser without oiliness
- Silver nanoparticles = antibacterial properties-> added to polymer fibres to make masks, deodorant etc
What are the effects of Nanoparticles on health?
- lack of investigation on effects (long term?), label products to show use of nanoparticles
- Suncreams-> protect from UV, better coverage, may damage cells, may damage environment when washed away
