# Why does Mg2+ have the ionic radii bigger than Ca2+

If they were atoms, $\ce{Mg}$ should have a smaller radii. How does this change?

• Can you point to a source that says calcium ion is smaller than magnesium ion? – Brinn Belyea Feb 16 '15 at 3:59
• An exercise book.Also look here: answers.yahoo.com/question/index?qid=20071216145936AAgZZnv "To answer your question: (out of Ca2+ and Mg2+ )Mg2+ is larger because it they are cations and Mg is above Ca;" – user13411 Feb 16 '15 at 4:08

Ca2+ is bigger than Mg2+

as shown in the above pic Mg2+has more smaller size then Ca2+... I'm sorry but your question is wrong, Why Ca2+ has bigger Ionic Radii then Mg2+? because

No of Shells increases down the group

-Property of Periodic table

therefore ->

As you move down a group in the periodic table , additional layers of electrons are being added, which naturally causes the ionic radius to increase as you move down the periodic table.

you can check reference this for more information

Image source : http://searchpp.com/ionic-radii-periodic-table/

Mg is smaller the Ca because it is above it in the periodic table, magnesium being a period above it shows that it has one less electron shell so it's smaller, calcium has another ring of electrons, as to say, that are around it so it's radius would be bigger. Your question is wrong.