Memory Anchor:

• Super Challenge:

  Stretch:

  Challenge:

Key Questions:

1. What can lead to a scientific model being changed or replace?
   • New experimental evidence may lead to a scientific model being changed or replaced.
2. What is an atom?
   • The word atom means indivisible. An atom is the smallest constituent unit of ordinary matter.
3. What were the main features of the 'plum pudding' model of the atom?
   • In the plum pudding model the atom was thought to be a sphere of positive charge with negatively charged electrons dotted around inside it like plums in a pudding.
4. How did the 'plum pudding' model describe the structure of an atom?
   • The plum pudding model suggested that the atom is a ball of positive charge with negative electrons embedded in it.
5. How did the Rutherford's alpha particle scattering experiment change our understanding of the structure of the atom?
   • A beam of alpha Particles was aimed at very thin gold foil and their passage through the foil detected. The scientists expected the alpha Particles to pass straight through the foil, but something else also happened. Some of the alpha Particles emerged from the foil at different angles, and some even came straight back. The scientists realised that the positively charged alpha Particles were being repelled and deflected by a tiny concentration of positive charge in the atom. As a result of this experiment, the plum pudding model was replaced by the nuclear model of the atom.
6. What contribution did Niels-Bohr make in furthering our understanding of the structure of the atom.
   • Niels-Bohr adapted the nuclear model by suggesting that electrons orbit the nucleus at specific distances. The theoretical calculations of Bohr agreed with experimental observations.
7. Which subatomic particle gives the nucleus of the atom a positive charge?
   • Protons give the nucleus of the atom a postive charge, each proton has mass of 1 and a 1 charge.
8. What discovery did James Chadwick make that advanced our understanding of the structure of an atom?
   • James Chadwick provided evidence that the nucleus of an atom was also made of neutrons. Protons were discovered some 20 years prior.
9. How did the evidence of alpha particles scattering lead to a change in the atomic model?
   • The new evidence of alpha Particles scattering during the gold leaf experiment lead to a new atomic model as it proved most of the atom was empty space except for a postive charge at the very centre of it.
10. Describe the currently accepted structure of the atom
    • A nucleus composed of protons and neutrons, surrounded by shells of electrons.