Using only the periodic table arrange the following elements in order of increasing ionization energy

Question

lowest to highest

xenon, tin, tellurium, indium

Answer 1

Hi Alexandria!

Ionization energy can be defined as the amount of energy (in kJ/mol) required to remove an electron from an atom. The easiest way to think about this, in my mind, is to consider the overall charge of the nucleus based on the number of protons it has! If there are more protons, there is a larger overall positive charge, and a stronger attraction of the nucleus to the electrons. The strength of that nucleus charge - electron interaction is what determines the amount of energy required to remove an electron. Basically, the ionization energy must exceed that attraction.

The general trend of ionization energy is increasing from left to right and bottom to top (following the atomic radius trend), which means that the bottom left elements would have the lowest ionization energy. Based on that information, the correct arrangement would be In < Sn < Te < Xe.

Answer 2

In general, ionization energy decreases as you go down and to the left in the periodic table. Because all of the elements belong to the same row, the ionization energy of the leftmost elements would be the lowest if you only use the periodic table to guess. So, you would order the elements from left to right in that row from the periodic table to show increasing ionization energy.

In reality this rule is more of a guideline and does not hold up to scrutiny because things like how the electron orbitals behave add more complexity. If all that you have learned in the class focusses only on the periodic table, you probably are not expected to know this.