Atomic structureIB MYP Physics: Subtopic test

1. 1
   A teacher in Nairobi builds a model of a lithium atom for her class. Her atom has 3 protons and 4 neutrons and is electrically neutral.

   (a)

   Which particles are found in the nucleus of this lithium atom?

   [1 mark]

   • AElectrons and protons
   • BProtons and neutrons
   • CNeutrons and electrons
   • DProtons only

   (b)

   What is the mass number of this lithium atom?

   [1 mark]

   • A3
   • B4
   • C6
   • D7

   (c)

   State the number of electrons in the lithium atom and explain why the atom has no overall charge.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   In 1909 Hans Geiger and Ernest Marsden, working with Ernest Rutherford, fired alpha particles at a very thin sheet of gold foil and counted where the particles ended up. Almost all of the alpha particles passed straight through. A very small number were deflected through large angles, and a very few bounced almost straight back.

   (a)

   What does the fact that almost all of the alpha particles passed straight through the foil show about gold atoms?

   [1 mark]

   • AMost of an atom is empty space
   • BAn atom is a solid ball of positive charge
   • CElectrons are heavier than alpha particles
   • DThe nucleus fills most of the atom

   (b)

   Which earlier model of the atom did these results show to be wrong?

   [1 mark]

   • ADalton's solid sphere model
   • BBohr's model with electrons in shells
   • CThe plum pudding model
   • DThe nuclear model

   (c)

   Explain why a small number of the alpha particles were deflected through large angles.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   A student compares three neutral atoms. Atom X has 6 protons and 6 neutrons. Atom Y has 6 protons and 8 neutrons. Atom Z has 7 protons and 7 neutrons.

   (a)

   Identify which two atoms are isotopes of the same element and justify your answer.

   [3 marks]

   (b)

   Atoms with 6 protons are carbon atoms. Write the nuclide notation for atom Y, and explain why atoms X and Y have the same chemical properties.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   Before 1909, many scientists accepted J. J. Thomson's plum pudding model, in which an atom is a ball of positive charge with tiny electrons embedded in it like fruit in a pudding. This model predicted that alpha particles fired at thin gold foil would pass through with only very small deflections. Geiger and Marsden found that most alpha particles went straight through, a small number were deflected through large angles and a very few bounced back.

   (a)

   Explain how the results of the gold foil experiment led Rutherford to propose the nuclear model of the atom.

   [6 marks]

   (b)

   Evaluate whether it was worthwhile for scientists to develop the plum pudding model, even though it was later replaced.

   [6 marks]

   Total for question 4: 12 marks

End of questions