C3 Structure and Bonding Flashcards
(54 cards)
What are the different methods of changing state?
Freezing - liquid to solid
Melting - solid to liquid
Condensing - gas to liquid
Boiling - liquid to gas
Sublimation - solid to gas
Deposition - gas to solid
What happens when a substance condenses?
- Thermal energy is lost
- Particles move slower and closer together
- Some forces are stronger, some particles touch because of the stronger force of attraction
What happens when a substance melts?
- Particles gain thermal energy + move more
- Some forces between particles are overcome
- Particles move other each other
What happens when a substance boils?
- Particles gain more energy and move more
- Remaining forces between particles are overcome
- Particles move far apart
How do particles move as a solid, liquid and gas?
Solid - vibrate at a fixed point
Liquid - vibrate and move in a fixed volume
Gas - vibrate and move rapidly in random directions.
What are the formulas and charges of the polyatomic ions?
- OH - hydroxide (-)
- CO3 - carbonate (2-)
- NO3 - nitrate (-)
- SO4 - sulfate (2-)
- NH4 - ammonium (+)
- H - hydrogen (+)
How do you work out the formulae of ionic compounds?
Ionic compounds contain positive and negative ions which form an overall neutral particle. There must be an equal amount of positive and negative charges in the compund meaning there are more of some ions than others in sone ionic compounds, e.g lithium oxide is Li2O.
What is ionic bonding?
The strong electrostatic force of attraction between oppositely charged metal and non-metal ions.
What are cations and anions?
cations - positively charged ions
anions - negatively charged ions
How do you draw ionic bond diagrams?
You draw ions of the equivalent amount to the number of ions in the formula. e.g for MgF2 you draw one magnesium ion and 2 fluoride ions together, remembering to label charges and use square brackets.
What is the structure of any ionic compound?
A giant ionic lattice - large numbers of ions are regularly arranged in a repeating pattern.
What is the melting point of giant ionic lattices? Why?
The melting point is very high because of the large amounts of energy needed to overcome the many strong electrostatic forces of attraction throughout the salt crystal.
Mention
* Strength (+ number) of bonds or forces
* Amount of energy required to overcome bonds or forces
* Therefore, high or low melting point
Do giant ionic lattices conduct electricity?
Ionic compounds can only conduct when molten (liquid) or dissolved in solution, as ions are free to move and carry a charge throughout the circuit/material.
What is metallic bonding?
The strong electrostatic attraction between positive metal ions and negative delocalised electrons.
What is the structure of giant metallic structures?
Giant metallic structures are formed of regular layers of positive metal ions surrounded by a sea of delocalised electrons. You draw this by as a diagram by drawing rows of circles (+ metal ions) with a plus inside surrounded by minuses (electrons) to represent the + ions surrounded by delocalised electrons.
Do giant metallic structures have a high or low melting point? Why?
High melting point as a lot of energy is required to overcome the strong electrostatic forces of attraction between + ions and - delocalised electrons.
Do giant metallic structure conduct?
Yes, delocalised electrons carry electrical charge and thermal energy through the metal.
Are pure metals ductile and malleable?
Ductile and malleable because:
* arranged in layers/rows
* atoms/ions are the same size
* layers can slide over each other easily when a force is applied
Why are alloys stronger and harder the pure metals?
There are different sized atoms so the layers cannot slide past each other as easily.
How is a covalent bond formed?
When 2 atoms share a pair of electrons
How do you draw dot and cross diagrams for covalent bonds?
Draw outer shell electron structures for each atom overlapping with shared electrons in the overlap (one atom crosses, other dots)
What are small/simple molecules?
Contain only a few atoms held together by covalent bond.
Why is carbon dioxide a gas at room temperature?
- Simple molecules
- Have weak intermolecular forces
- Little energy is needed to overcome these weak forces
- so CO2 boils at very low temperatures
Do simple molecules conduct?
Do not conduct electricity because there are no charged particles - only neutral molecules