Answer;
From highest to lowest is Li>Na>K>Rb.
Step-by-step explanation;
- Ionization energy is the energy that is required to dislodge or remove an electron from the outer most energy level or energy shell. The first ionization energy is the energy required to remove the first electrons from the outermost energy shell.
- Lithium will have the highest first ionization energy, as the outer electron is closer to the pull of the nucleus and not shielded by full shells. This means that rubidium will be the lowest.