Isoelectronic

[Melissa Papuc 2J]

If two atoms are isoelectronic, how do you know which ion has the larger radius? For example, Na+, Mg2+ and F- are all isoelectronic. How would you rank these ions from smallest to largest?

[Alex Nguyen 3I]

You would look at the atomic number. The higher the atomic number, the higher the nuclear charge. This means that the nucleus will pull on the electrons more, making the atom/ion smaller because of the tightness.

[Emily Chu 3E]

Like what was said above, when there is an increase in protons, the ionic radius decreases. This is because the more protons there are, the greater the nuclear charge - meaning that the electrons are pulled closer towards the nucleus. In this specific problem, Mg2+ would have the smallest atomic radius, then Na+, and lastly, F- .