Final answer:
The correct order for first ionization energies from largest to smallest is Br, Se, K, Ca, Kr.
Step-by-step explanation:
The correct order for first ionization energies from largest to smallest is:
- Br
- Se
- K
- Ca
- Kr
The first ionization energy refers to the energy required to remove one electron from an atom in its gaseous state. It is generally higher for atoms that have a smaller atomic radius and a higher effective nuclear charge. In this case, Br has the largest first ionization energy because it has a smaller atomic radius and a higher effective nuclear charge compared to the other elements. Se has the second largest first ionization energy, followed by K, Ca, and Kr.