Describe the plum pudding model of the atom.
Write the three subatomic particles (electrons, neutrons, and protons) in order of their discovery, from earliest to latest.
The discovery of isotopes explained why some relative atomic masses are not whole numbers.
Element QQQ has two isotopes. The table below shows the mass numbers and percentage abundances of the isotopes of element QQQ.
| Mass number | Percentage abundance (%) |
|---|---|
| 69 | 60.1 |
| 71 | 39.9 |
Calculate the relative atomic mass (ArA_rAr) of element QQQ. Give your answer to 1 decimal place.