Topic 1 Flashcards
John Daltons Atomic theory 1803
Matter is made of atoms which are tiny particles which cannot be created, destroyed or divided
Atoms of the same element are identical, and atoms of different elements different
Different atoms combine together to create new substances
Who discovered the electron
JJ Thompson
Discovery of the electron
JJ Thompson discovered the electron by using a cathode ray tube which identified th electron as a negatively charged particle hence proving that atoms are divisible
Thompsons model after discovering electron
Plum pudding model : negative electrons spread through positively charged material
Who discovered the nucleus
Ernest Rutherford
The discovery of the nucleus
Gold foil experiment
Rutherford shot a beam of positively charged particles at a thin sheet of gold foil and based on the plum pudding model expected the particles to pass through the foil because the positive charge of the nucleus was thought to be evenly spread out
Some particles scattered however and a few were deflected directly back which led to the idea that most of the atoms mass is centred in the nucleus
The Bohr model
Niels Bohr further develop Rutherford concept and suggested that electrons orbit in shells
This model showed why the nucleus does not collapse inwards
Proton relative mass
1
Neutron relative mass
1
Electron relative mass
1/1840
Proton charge
+1
Neutron charge
0
Electron charge
-1
Atomic number
The number of protons in the nucleus of the atom
Mass number
The sum of the number of protons and neutrons in an atom
Relative atomic mass calculations
(%of isotope a x mass of isotope a) + (% of isotope b x mass of isotope b) / 100