Consulting the Data Booklet is useful for answering this question. In the Periodic Table, the elements radon (Rn), francium (Fr) and radium (Ra) are arranged in successive proton numbers. In which order do their first ionisation energies occur?
- AFr → Ra → Rn
- BFr → Rn → Ra
- CRa → Fr → Rn
- DRn → Ra → Fr