Which elements have 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. read more

- Elements in human body: 5,525: Neodymium: Nd: 60 - Covalenz radius: 5,5387: Cerium: Ce: 58 - Ionization energy: 5,5769: Lanthanum: La: 57: For chemistry students and teachers: The tabular chart on the right is arranged by Ionization energy. The first chemical element is Cesium and the last one is Helium. The unity for ionization energy is eV. read more

Ionization energy is the amount of energy required to remove one electron from an atom. So the groups further to the right of the periodic table would have greater ionization energies because they are more stable, so they don't want to lose electrons, and there is a greater number of protons attracting the negative charges (the electrons). read more

Understanding ionization energy is important because it reflects an element's ability to participate in some chemical reactions or form some compounds. If you must determine which element from a list has the highest ionization energy, find the elements' placements on the periodic table. read more