How do you determine if an ion is larger?

For example, which ion is larger in each pair?
#Ca^(2+)#, #Mg^(2+)#
#Cl^-#, #P^(3-)#
#Cu^+#, #Cu^(2+)#

Answer 1

#"A priori"#, the more positive the cation, the SMALLER should be the ion...........

The cationic radius should decrease in relation to the atomic radius because the formation of a cation necessitates the loss of an electron, which is taken out of the valence shell and no longer available to shield the nuclear charge.

The valence should expand, resulting in an anion having a larger radius than its parent atoms, when an atom is reduced and takes electrons into its valence shell to form an anion.

For the alkaline earth cations, #Mg^(2+)#, and #Ca^(2+)#, you have a third Period cation versus a fourth Period cation. Clearly, the calcium ion should be larger! (Of course the ionic radius is reduced with respect to the parent atom, but this is not what we were asked to consider!).
For non-metal ions, #Cl^-#, and #P^(3-)#, you have third row anions. The more negative phosphide should be larger, in that (i) it has a reduced nuclear charge, i.e. #Z# is smaller, and (ii) it is trinegative rather than singly negative. If we were to consider the neutral atoms, certainly #Cl# would be the smaller atom. Why?
For #"cuprous"#, #Cu^+#, and #"cupric"# ions, #Cu^(2+)#, the dication should be SMALLER, as explained in the last section.
To end, you are a chemist, a physical scientist. We have considered some of the possible effects of ionic charge. It is up to you to consult the data, and find some actual measurements of ionic radii to see that we haven't got it #"backasswards"#. Here is a start, but you must consider the data.
Sign up to view the whole answer

By signing up, you agree to our Terms of Service and Privacy Policy

Sign up with email
Answer 2

Compare the number of electrons. More electrons result in a larger ion.

Sign up to view the whole answer

By signing up, you agree to our Terms of Service and Privacy Policy

Sign up with email
Answer from HIX Tutor

When evaluating a one-sided limit, you need to be careful when a quantity is approaching zero since its sign is different depending on which way it is approaching zero from. Let us look at some examples.

When evaluating a one-sided limit, you need to be careful when a quantity is approaching zero since its sign is different depending on which way it is approaching zero from. Let us look at some examples.

When evaluating a one-sided limit, you need to be careful when a quantity is approaching zero since its sign is different depending on which way it is approaching zero from. Let us look at some examples.

When evaluating a one-sided limit, you need to be careful when a quantity is approaching zero since its sign is different depending on which way it is approaching zero from. Let us look at some examples.

Not the question you need?

Drag image here or click to upload

Or press Ctrl + V to paste
Answer Background
HIX Tutor
Solve ANY homework problem with a smart AI
  • 98% accuracy study help
  • Covers math, physics, chemistry, biology, and more
  • Step-by-step, in-depth guides
  • Readily available 24/7