Atomic Structure Flashcards
Scientists
John Dalton William Crookes George Johnstone Stoney J.J Thomson Robert Milikan Ernest Rutherford Niels Bohr James Chadwick
John Dalton- discovered
Atomic theory
John Dalton - how
Through experiments he performed with gases
William Crookes - discovered
Cathode rays
William Crookes - how
Negative electrode rays cast shadow of maltese cross in a vacuum tube
George Johnstone Stoney - discovered
Named the electron
George Johnstone Stoney - how
Proposed name in 1981
J.J Thomson - discovered
Electrons have a negative charge
J.J Thomson - how
- Sent cathode ray through positive electrode, then through 2 parallel plates
- When plates weren’t charged, ray went straight through, but if top one was positive, ray went upwards
Robert Millikan - discovered
Magnitude of charge of electrons as shown by oil drops experiment
Robert Millikan - how
- Sprayed tiny oil droplets between 2 charged metal plates, used x-rays to ionise air between plates
- Oil droplets fell through air
- Oil droplet attached to positively charged plate
- Made the droplet stationary + from measurements, he was able to calculate charge of electron
Ernest Rutherford - discovered
Discovering of nucleus as shown by particle scattering experiment, discovering of protons in nuclei of various atoms
Ernest Rutherford - how
- Bombarded gold foil with Alpha particles
- used detector for scattered a-particles
- most went straight through, some deflected largely, some reflected
- showed that gold foil had nuclei - which when hit, positive alpha particles repelled them
Niels Bohr - discovered
Model of atom
Niels Bohr - how
Used experimental evidence to prove electrons occupy particular orbits or shells around nucleus of atom
James Chadwick - discovered
Discovered the neutron
James Chadwick - how
- Bombarded beryllium with alpha particles
- Discovered some particle with no charge was coming from beryllium
- They were knocking protons from beryllium
- Found that these particles had same mass as protons + named them neutrons
Dalton’s Atomic Theory
- All matter is made up of very small particles called atoms
- All atoms are indivisible. Cannot be broken down into simpler particles
(3. identical atomic mass for particular element)
Thomson’s plum pudding
- Atom is like a sphere of positive charge
2. Electrons embedded in sphere at random
Problem with Plum Pudding model
Explained why atoms were neutral but Thomson did not have experimental evidence
Mass Spectrometer
Instrument capable of separating + recording relative amounts of isotopes of an element.
Mass Spectrometer topics (processes)
Sample intro Vaporisation Ionisation Separation of ions Detection
Mass Spectrometer
- Sample to be analysed is injected into instrument
- Vaporised
- Ionised by bombardment with beam of high-energy electrons.
- Positive ions produced are accelerated through slit, using electric field, deflected along circular path using magnetic field
- Degree of curvature depends on mass of ion)
- Separated into beams of ions of similar masses in this way
- Detected electronically
- Vacuum inside so ions don’t clash with air molecules