# Question #7eca9

##### 1 Answer

You may work it out from the "size" of each atom's nucleus and the electrons around it, or look it up in a table.

#### Explanation:

We know that the atoms generally decrease in size as they move left-to-right in a row of the Periodic Table of the Elements, and increase as they move down in a column, or Group. There is a sharp reversal going from the last element in a row to the first one of the next row.

Once the initial atomic sized are determined, we can observe that adding electrons (- charges) will increase the effective size, and removing them (+ charges) will decrease the effective size.

Given:

"Normal" sequence (decreasing):

First Row:

Second Row:

Ionic changes in each row:

So, relatively,

Considering the effect of charge balance, more electrons relative to protons (-) expand the radius, and fewer electrons (+) decrease the effective radius.

Thus, "isoelectronic" atoms can be compared:

*more* than

*more* than

*more* than

Thus, the final order of the relative size of the ions listed is:

Actual values (picometer):

http://abulafia.mt.ic.ac.uk/shannon/ptable.php