History of the Atom

Question 1

Summarise Dalton’s work

Answer 1

• Solid sphere model
• ‘indivisible building blocks’
• in an element all atoms are exactly alike
• all elements are made up of the same atoms

Question 2

Summarise Thompson’s work

Answer 2

• plum pudding model (cathode ray tube)
• mass of e- much smaller than mass of the atom
• particles have a charge
• positively charged sphere in which negatively charged electrons float

Question 3

Summarise Rutherford’s work

Answer 3

• gold foil experiment (fired alpha particles at gold foil)
• discovered positive nucleus
• most of atom is empty space
• mass concentrated in nucleus

Question 4

Summarise Bohr’s work

Answer 4

• atomic model
• shows electrons in fixed shells outside of nucleus
• each circle has an energy level, further from nucleus = more energy