19. Radioactivity: Model of the Atom

Question 1

How has the Theory of Atomic Structure changed over time? What is Plumb Pudding Model

Answer 1

• 1897: JJ Thompson - Plumb pudding model - atoms spheres of positive charge with tiny negative electrons stuck in them

Question 2

Rutherford and Marsden Theory? - Nuclear Model

Answer 2

1909: R and M - Fired alpha particles at thin gold foil. From Plumb P they expected them to pass through but they were deflected and some deflected back from where came - Plumb model couldn’t explain

• Most of mass of the atom concentrated at centre in a tiny nucleus
• Most of atom empty space
• Nucleus has positive charge because repelled positive alpha particles
• Led to creation of the Nuclear Model of the atom

Question 3

Niels Bohr model?

Answer 3

• Electrons in fixed orbit at set distances from nucleus
• Distances called Energy Levels
• Electrons can only exist in these orbits or shells and not anywhere in between