The graph below illustrates how the first ionisation energy changes with proton number for some elements. The letters shown are not the normal symbols for the elements. Which statement about the elements is correct?
- 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.