Fundamental particles, mass number and isotopesAQA A-Level Chemistry: Mind map

Exam questions on Fundamental particles, mass number and isotopes

1. In 1909 Geiger and Marsden, working with Rutherford, fired a beam of positively charged alpha particles at a very thin sheet of gold foil and recorded where each particle landed using a detector screen. At the time, the accepted 'plum pudding' model pictured an atom as a sphere of positive charge with electrons embedded throughout it.
   Explain how the results of this experiment led scientists to conclude that the nucleus is positively charged and that it contains most of the mass of the atom.2 marks
2. A forensic laboratory identifies an iron compound in a paint sample. The iron is present as the ion ⁵⁶Fe³⁺, and the analyst's data sheet gives the atomic number of iron as 26.
   A second sample contains the ion ⁵⁴Fe²⁺. State the number of protons, the number of neutrons and the number of electrons in one ⁵⁴Fe²⁺ ion.2 marks
3. Magnesium has three naturally occurring isotopes, ²⁴Mg, ²⁵Mg and ²⁶Mg. A chemist is comparing atoms of these isotopes. The atomic number of magnesium is 12.
   Explain what is meant by the term isotopes, and state the number of protons, neutrons and electrons in an atom of ²⁵Mg.3 marks