Structure And Bonding Flashcards
What are simple molecular substances
Small clusters of two or more atoms Joined together giving them low melting and boiling points . Although there are strong bonds within the molecules the forces between the molecules are weak and do not require much heat energy to overcome them
What are giant structures
Substances with an unlimited continuous lattice of particles with strong bonding throughout the structure . This gives them
High melting and boiling points so a lot of heat energy is needed to overcome this strong bond
How are ionic compounds arranged
Giant ionic structure in a lattice through syringe electrostatic forces between the charged ions
Why do ionic compounds have high melting and boiling points
Giant structure with strong electrostatic attraction between oppositely charged ions makes them difficult to break
Why are ionic compounds hard
Strong Electro static attraction between oppositely charged ions makes them difficult to break apart
Why are ionic compounds brittle
To reshape a solid ,layers of particles must slide past each other . This slides positive over postive which then repel each other and the crystal shatters
Why are ionic compounds soluble in polar solvents
Charged end of solvent molecules are attracted to the ions in the solid and pull them away from other ions in the lattice
Why are they electrical conductors when molten or in solution
When an ionic solidis melted or dissolved the ions break free from the lattice and are able to move around . The free moving charged particles enable the liquid or solution to conduct electricity
What happenes to the melting point of an ionic substance
More charges means more attraction and therefore more heat energy is required to break the bonds
Where is metallic bonding found
In all metals and alloys
What happens in metallic bonding
Each metal looses its outer shell electrons and becomes a positive ion. The positive ions are packed in a lattice and the cloud of delocalised electrons move throughout the entire metal .the electrostatic attraction between the positive metal ions and the cloud of delocalised electrons holds the metal together
Why have metallic compounds for high melting boiling points and are strong
Giant structure with strong electrostatic forces between positive metal ions and delocalised electrons requires a large amounts of heat energy to break
Why are metallic compounds malleable
The layers of metal ions can slide over each other easily without disrupting the metallic bonding ,the metal still consists of a regular lattice of positive metal ions surrounded by a cloud of delocalised electrons
Why are metallic bonding electrical compounds
Cloud of delocalised electrons is free to move through the entire metal carrying the electric current
How are covalent substances structured
Most are simple covalent molecules but some are giant covalent structures
Why do simple covalent molecules have low melting and boiling points
Strong covalent bonds between atoms to form molecules but weak intermolecular forces which require little energy to overcome
Why are Simple covalent molecules soft
To break apart a simple molecular solid it is not necessary to break the strong covalent bonds that hold the atoms together but only the weak intermolecular forces which requires a small force
Why are simple covalent molecules electrical insulators
There are no ions present and all electrons are localised on atoms or in the covalent bonds so there are no free moving particles to carry the electric current
Why are covalent molecules soluble in non polar solvents
Do not contain ions so are mole soluble in non polar solvents
How is diamond structures
Giant lattice which each carbon forimung 4 covalent bonds
Why had diamond and graphite got a high sublimation temperature
To break down the giant structure requires strong covalent bonds between the atoms to be broken which requires a large amount of heat energy . This results in single carbon atoms with no bonds between them so turns directly to gas
Why is diamond hard
To break the structure requires a large number of strong covalent bonds to be broken which requires a large force
Why is diamond and graphite insoluble in all solvents
To dissolve the substance would require strong covalent bonds between the atoms and no solvent is strong enough for this
Why is diamond an electrical insulator
All electrons are localised in covalent bonds so there are no free moving charges particles to carry an electric current
What are uses of diamond
Coating saw blades and drill bits extreme hardness allows it to cut through Anything
How is graphite arranged
Later lattice each carbon atom forming 3 covalent bonds to carbon atoms
Why is graphite soft
Covalent bonds within the layers are difficult to break but each layer is held next to each other by weak forces so the layers are therefore easily separated
Why is graphite an electrical conductor
Each carbon forms only 3 bonds leaving one free electron that can move throughout the structure and carry an electric current
What are uses if graphite
Lubricating oils ,pencil lead as the weak forces between layers allows the layers to slide over each other easily or rub onto paper
What does an alloy do
Different sized atomms distort the layers in the structure and make it harder for atoms to slide over each other
What does more free electrons do to electrical conductivity
Increases as there are more free electrons for current to flow through . Higher atomic number within groups means better electrical conductor
Why are metals malleable
If a large force is applied the layers of atoms slide over each other and stay in their new positions as the cloud of delocalised electrons continues to attract and hold the positive joins together
