The graph illustrates how the first ionisation energy changes with proton number for several elements. The letters shown are not the actual symbols of the elements. Which statement about these elements is the correct one?
- AP and X are in the same period in the Periodic Table.
- BThe general increase from Q to X is due to increasing atomic radius.
- CThe small decrease from R to S is due to decreased shielding.
- DThe small decrease from U to V is due to repulsion between paired electrons.