The element phosphorus has the greatest first ionization energy.
What is the first ionization energy?
The first ionization energy of an element is the energy that is required to remove an electron from the outermost shell of an atom of the element.
We know that ionization energy decreases down the group but increases across the period thus the element phosphorus has the greatest first ionization energy.
Learn more about ionization energy:https://brainly.com/question/16243729?
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