Structure Of The Atom Flashcards
Give evidence for atoms.
- Brownian motion
- The ability of kinetic theorey to explain properties of matter eg gas pressure, diffusion
Give evidence for electrons. Explain the experiment.
Thermionic emission:
- negative particles - electrons - released from cathode.
- attracted to an anode and absorbed, forming a current in the circuit
- Thomson found electrons were easily deflected a lot by a magnet, showing they were extremely light.
Who proposed the plum pudding model, and what is the plum pudding model?
- Thomson proposed the plum pudding model.
- The plum pudding model depicts negative electrons embedded in a positively charged material.
How did Thomson come up with the Plum Pudding model - what did he realise?
Thomson realised that since atoms are neutral, if they contain negative electrons, they must also contain some positive part.
What did Rutherford do in 1909 to investigate the scattering of alpha-particles and what part of the atom was discovered through this?
- in 1909 Rutherford investigated the scattering of alpha-particles by firing them at thin metal foils, including gold.
- he discovered the nucleus
Describe Rutherford’s alpha particle scattering experiment
Rutherford’s alpha particle scattering experiment
- A narrow beam of alpha-particles from a radium source hit a thin sheet of gold foil.
- The detector had a glass screen covered with zinc sulphide.
- Any alpha particle hitting the screen caused a flash of light which was seen through a microscope.
Outline the results of Rutherford’s alpha particle scattering experiment (3 marks)
- most a-particles passed straight through or deflected at very small angles
- 1 in 8000 were deviated more than 90 degrees
- some bounced straight back
Which experiement did Rutherford discover the nucleus from?
Rutherford’s alpha particle scattering experiment
What did Rutherford propose in 1911?
In 1911 Rutherford proposed that an atom has a positively charged core (nucleus) which contains most of the mass of the atom and is surrounded by orbiting electrons.
Describe the Rutherford-Bohr model of the atom. How many electrons can fill each shell in an atom?
Electrons occupy only certain allowed orbits in the atom.
A nucleus is surrounded by shells filled by orbiting electrons.
The first shell holds 2 electrons. The second shell holds 8 electrons. The third shell holds 18 electrons.
Give the location, relative mass and relative charge of a proton.
Proton.
Location - Nucleus
Relative mass - 1
Relative charge - +1
Note that mass and charge are measured in comparison with the proton.
Give the location, relative mass and relative charge of a neutron.
Neutron
Location - nucleus
Relative mass - 1
Relative charge - 0
Note that mass and charge are measured in comparison with the proton.
Give the location, relative mass and relative charge of an electron.
Electron
Location - shells, orbiting the nucleus
Relative mass - 1/1840
Relative charge - -1
Note that mass and charge are measured in comparison with the proton.
Outline how a nucleus is represented. (Clue - A, Z, X)
X - chemical symbol for the element concerned
A - atomic mass number (number of protons and neutrons in the nucleus)
Z - atomic number (number of protons in the nucleus)
Structure is as shown below:
A
X
Z
What is the definition of an isotope?
Isotopes are atoms with the same number of protons but different numbers of neutrons. They have the same Z (atomic number) but different A (atomic mass number).
Since they have atoms of the same atomic number they are atoms of the same element.
