Topic 1 Flashcards
What is an element
Elements consist of atoms with the same atomic number
How to calaculate relative atomic mass
Sum of (isotope abundance x isotope mass number
_______________________
Sum of abundances of all the isotopes
What is a compound
A substance formed by two or more atoms that are chemically bonded together
What is a mixture and how can they be separated and give examples
A mixture has no chemical bonds and can be separated by physical methods eg filtration,crystaliseation,fractional distilleration,chromatography
What is filtration and give an example
Filtration separates insoluble solids from liquids
It can be used for purification
What is the first way you can separate soluble solids from solutions
Evaporation
Pour solution into evaporating dish
Heat solution,solvent will evaporate then getting more concentrated,the crystals will form
Keep heating till your left with dry crystals
What is the second way you can separate soluable solids from solutions
Crystallisation
Pour solution into evap dish ,gentally heat ,some solvent will evap making solution more concentrated
When you see crystals start to form remove dish from heat and leave to cool
Salt should start to form crystals as it becomes insoluble to cold and place in warm place to dry
What is fractional distilleration
Used to separate a mixture of liquids
Decribe the practical of distilleration
put mixture in flask and put fracturing column on top then heat it
Diff liquids will have diff boiling points and evap at diff temps
Liquid with lowest boiling point evap a first ,when the temp on thermometer matches boiling point of liquid it will reach top of column
When first liquid has been collected raise temp UNTILL next one reaches top
Who described atoms as solid spheres
John dalton
What did jj Thomson conclude from his exeripemts
That atoms wernt solid spheres
His measurements of charge and mass shows that an atom must contain even smaller and negatively charged particles
What did the solid sphere idea get changed to
Plum pudding model
What does the plum pudding model show
Ball of positive charge with electrons stuck in
What did Rutherford show
That the plum pudding model is wrong
In 1909 what happened
Rutherford and marsden conducted alpha particle scattering experiments
What is the alpha particle scattering experiments
Fired positvely charged alpha particles at and extremely thing peice of gold
How did the alpha particle scatting experiment prove that the plum pudding wasn’t right
The expectation was that only the particles would pass through the sheet or be slightly deflected due to the positive charge of each atom being spread out
However while most going through some were deflected more than expected and a small number were deflected backwords so plum pudding couldn’t be right
What idea did Rutherford come up with to explain this new evidence
The nuclear model
Where there’s a tiny positively charged Nucleas at the centre where most mass is concentrated
How did rutherfords nuclear model differ from bohrs model
Rutherford thought that electrons clouded the nucleus so most of atom is empty space
Bohr suggest that electrons were in shells that orbit the nucleus
In the 1800 how were elements arranged
By atomic weight
How were the early periodic tables wrong
They were not complete and some events were places in wrong group due to elements being placed in order of atomic weight and did not take into account of their properties
Why were gaps left in dmitri Mendeleev table of elements
Because there was undiscovered elements and allowed Mendeleev to predict what properties they had
What are group 1 called
Alkali metals
What are the properties of the group 1 element
Soft ,low density and the first 3 elements are less dense than water
