Atomic theory 3 Flashcards
What is an alpha particle (L.C)?
Particle consisting of two protons and tow neutrons
Why did Mendeleev place tellurium before iodine in his periodic table of elements? (L.C)
Chemical properties matched (fitted) better in that order
On the basis of the plum pudding model of atomic structure, what results were expected by Rutherford when thin gold foil was first bombarded with alpha particles in 1909? (L.C)
Alpha particles were expected too pass straight through
How did the actual result of Rutherford’s experiment differ from the expected result? (L.C)
- Some alpha particles were deflected at large angles
- A few alpha particles were reflected along original path
How was the model of atomic structure changed as a result of Rutherford’s experiment? (L.C)
- Atoms are mostly made up of empty space with small nucleus
What was the purpose of Millikan’s oil drop experiment of 1908 to 1913? (L.C)
To measure the magnitude of charge on electron
Describe the plum-pudding model of the atom proposed by Thomson around 1897? (L.C)
Electrons in positive sphere (diagram needed)
Give one way of detecting the presence of cathode rays in a vacuum tube. (L.C)
Coloured light/glow
Name the scientist who around 1897 identified cathode rays as subatomic particles and, using a vacuum tube, measured their charge-to-mass ratio. (L.C)
J.J Thomson
What name was given to the subatomic particle that Thomson identified? (L.C)
Electron
State three observations made by Rutherford’s team when they bombarded gold foil with alpha-particles. (L.C)
- Most alpha particles passed straight through
- Some alpha particles were deflected at large angles
- A few alpha particles were reflected along original path
Explain how Rutherford deduced from his results that the nucleus is positive? (L.C)
Repulsion of positive alpha-particles
Explain how Rutherford deduced from his results that the nucleus is small and dense? (L.C)
Statistical analysis of angles of deflection
Describe the structure of Thomson’s ‘plum pudding’ model. (L.C)
Positively charged sphere with electrons embedded in it
What are alpha particles? (L.C)
Particles containing two protons and two neutrons
Explain why some of the alpha particles were deflected at large angles as they passed through the gold foil.
Repelled when passing near the nucleus
Why were some alpha particles reflected back along their original paths? Why did this only happen to a very small number of alpha particles? (Rutherford’s ‘gold foil’ experiment) (L.C)
Some - Collided with nucleus
Why - Nucleus is very small
Draw a labelled diagram to show the new structure of the atom proposed by Rutherford. (L.C)
- Draw
- Nucleus shown and labelled with one shell of electrons shown and labelled
Give two properties of cathode ray (L.C)
- Negatively charged
- High-speed
- Negligible mass