It is because of the shielding effect that the ionization energy decreases from top to bottom within a group.
From this trend, Cesium is said to have the lowest ionization energy and Fluorine is said to have the highest ionization energy (with the exception of Helium and Neon).
Which element has the highest ionization potential?
Ionization potential, thus, decreases down a group. The element with highest ionization potential in the periodic table is Helium (2372.1 kj/mol), while the element with the lowest ionization potential is Caesium (375.7 kj/mol).
Why does Group 8 have the highest ionization energy?
Inert gases, also known as “noble gases,” are the group 18 chemical elements on the periodic table. They are highly unreactive because its outermost atomic orbital has been filled to its maximum capacity of 8 electrons. Ionization energy is the energy required to remove a valence electron from an atom.
Why does helium have the highest ionization energy?
Helium has a structure 1s2. The electron is being removed from the same orbital as in hydrogen’s case. It is close to the nucleus and unscreened. The value of the ionisation energy (2370 kJ mol-1) is much higher than hydrogen, because the nucleus now has 2 protons attracting the electrons instead of 1.
Which element has the highest ionization energy?
The first ionization energy varies in a predictable way across the periodic table. The ionization energy decreases from top to bottom in groups, and increases from left to right across a period. Thus, helium has the largest first ionization energy, while francium has one of the lowest.
Photo in the article by “Wikimedia Commons” https://commons.wikimedia.org/wiki/File:Ionization_energies.png