Given elements:
Cl, Ne, Ge, Ca and Se
Chemistry -> The periodic table -> Periodic Trends: Ionization Energy
The ionization energy refers to the amount of energy needed to remove an electron from the valence shell of an atom.
Ionization energy increases as we go across a period and increases as we go up a group. This tred happens due to atomic radius, atomic number, electronegativy, among other properties.
Let's separate the period and group of each atom so we can predict the order of ionization energy.
Cl: Period 3 Group 17
Ne: Period 2 Group 18
Ge: Period 4 Group 14
Ca: Period 4 Group 2
Se: Period 4 Group 16
From the trend, we know that the atom that is higher and to the far right in the periodic table will have the greatest ionization energy. So, Ne that is in the 2nd period and 18th group will have the highest ionization energy.
Followed by Cl, since it is clores to Ne than the rest.
Then among the elements in the 4th period, we just have to analyse by their group. Se is farther to the right than Ge that is farther to the right than Ca.
In conclusion, the order by increasing ionization energy will be:
Final answer:
Ca < Ge < Se < Cl < Ne