Topic 1- Key Concepts Flashcards
Describe the gold foil experiment
- alpha particles were fired at a thin sheet of gold
- expected the particles to pass straight through or be slighly defelcted at most
- bc according to the plum pudding model the positive charge of each atom was thought to be spread out through the atom
- INSTEAD most particles did go through but a lot more than expected were deflected and some were deflected backwards
- meaning plum puddibg was wrong
- lead to the theory of nuclear atom- tiny +ive charged nucleus surrounded by a cloud of -ive electrons
What is an isotope?
Same number of protons but a different number of neutrons
What did Medeleev do?
- sorted elements by properties and in order of atomic mass
- left spaces for undiscovered elements
What are ions?
charged particles
What is ionic bonding?
When a metal donates electrons to a non-metal to form full outer shells. There is eletrostatic forces between the negatively charged non metal and postiviely charged metal. The attraction is called an ionic bond
What are proterties of ionic compounds?
- high melting point, due to strong attraction
- dont conduct electricity bc ions are fixed and can’t move
- unless they are dissolved in solution bc ions separate and are free to move in solution, so can carry electric charge
What is covalent bonding?
-a strong bond that forms when a pair of electrons is shared between two non metals to obtain full outer shells
Properties of simple covalent molecules?
- low melting + boiling points
- most are liquids or gases at room temp
- atoms within molecules are held together by strong covalent bonds
- intermolecular force of attraction between molecules are very weak
Properties of giant covalent structures
- very high melting + boiling points
- very hard
- don’t contain charged particles
- not soluble in water
Properties of Graphite
- each carbon atom forms 3 covalent bonds
- carbon atoms are arranged in layers- weak forces allow them to slide over each other
- no covalent bonds between layers only weak forces
- high melting point
- sea of delocalised electrons- so graphite can conduct electricity
Properties of Diamond
- each carbon atom forms 4 covalent bonds
- high melting point
- it is a rigid lattice structure- making diamond very hard
doesn’t conduct electricity bc it has no free electrons
Properties of graphene
- a single sheet of graphite
- 2d- just one atom thick
- a sheet a carbon atoms joined together in hexagons
What are fullerenes?
- they are moleculecules of carbon shaped like closed tubes or hollow balls
- they can cage other molecules
- can be used to deliver drugs direcctly to cells
- huge surface area
- could make great industrial catalysts
What is mettalic bonding?
- when metals lose outer shell electrons to form positive ions
- the positive ions are arranged in a regular pattern
- surrounded by a sea of delocalised electrons
- is the attraction between the positive ions and delocalised electrons
Properties of metals
- strong
- high melting + boiling points
- more dense than non metals
- can carry electrical charge
- malleable
What is conservation of mass?
- in a reaction no atoms are destroyed or created
Reasons for mass change
Mass increase- bc one of the reactants is a gas found in the air and products are solid, liquid or aqueous
Mass decrease- bc some or all of the reactants are solids, liquids or aqueous and at least one product is a gas
How to find mole
Mol= mass/mr
