# Problem: For the following set of atoms and ions, arrange the members in order of decreasing size: Rank items from largest to smallest. To rank items as equivalent, overlap them.Co3+ , Fe3+, Fe2+

###### FREE Expert Solution

Recall that ionic radius is the size of an ion. The trend for ionic radius is as follows: it increases from right to left and down a period in the periodic table. Ionic radius also increases with increasing number of electrons.

Co3+:

Co: atomic number = 27

neutral Co = 27 electrons

Co3+ = 27 e- - 3 e-

Co3+ = 24  e-

Fe3+:

Fe: atomic number = 26

neutral Fe = 26 electrons

Fe3+ = 26 e- - 3 e-

Fe3+ = 23  e-

Fe2+

Fe: atomic number = 26

neutral Fe = 26 electrons

Fe2+ = 26 e- - 2 e-

Fe3+ = 24  e-

Fe3+: → least # of electrons → smallest size

Co3+ and Fe3+ → same number of electrons → isoelectronic ###### Problem Details

For the following set of atoms and ions, arrange the members in order of decreasing size: Rank items from largest to smallest. To rank items as equivalent, overlap them.

Co3+ , Fe3+, Fe2+