Rank the following molecules/ions according to increasing 1st ionization energy. (lowest first, highest last) Mg, Ca, K, Li+, Rb
Explanation: Ionization energy is the amount of energy needed to take off an electron from the outer electron shell in an atom. Ionization energy increases from down up and to the right on the Periodic Table. Let's first deal with atoms and leave Li+ out for now. We can located the elements on the Periodic table and following our trend, up and to the right, we can arrange them Rb<K<Ca<Mg
Now let's take a look at Li+, A positive charge means that one electron was lost. Lithium has 3 electrons (atomic number) and with a positive charge Li+ has 2 electrons, which would place it in the neon (Ne) position (2 electrons). How is neon compared to the rest of the elements we just worked with? It will have the highest ionization energy. The trend will be Rb<K<Ca<Mg<Li+