What are the criteria for classifying compounds as ionic?

In summary, the compounds that are properly classified as ionic are MgCl2, K2O, HOCN, and NH4NO3. The general criteria for recognizing ionic compounds includes a large difference in electronegativity in binary compounds, and almost all salts being ionic in more complex compounds. While HOCN and NH4NO3 may have covalent bonds between individual atoms, they can also be expressed as ions, making them ionic compounds. Additionally, diatomic molecules such as Li2, Na2, and K2 have been reported in gaseous phase.
  • #1
skierboy
10
0

Homework Statement



Which of the following compounds are properly classified as ionic? (select all that apply)
HOCN
SF4
NH4NO3
MgCl2
K2O
Li2
NF3

Homework Equations



n/a

The Attempt at a Solution



My initial choices were MgCl2 & K2O ... however, since this was incorrect (it didn't tell me which were correct or incorrect - the entire problem was either correct or incorrect)... I'm guessing that HOCN and NH4NO3 might also classified as ionic.

If this is true, what is the general criteria for recognizing ionic compounds (if the compound has more than 2 types of atoms)?

Thanks!
 
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  • #2
skierboy said:
I'm guessing that HOCN and NH4NO3 might also classified as ionic.

Second for sure, not so sure about the first one.

If this is true, what is the general criteria for recognizing ionic compounds

In the case of binary compounds - large difference in electronegativity. In the case of more complex compounds - almost all salts are ionic.
 
  • #3
Li2?
Am I the only one who has never heard of that?

Is it something that can/does significantly exist in some laboratory in gas phase?
 
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  • #4
I believe I have seen not only Li2, but also Na2 and K2 reported in gaseous phase. But don't quote me, I can be wrong.

Edit:

K2 at webelements:

http://www.webelements.com/potassium/bond_enthalpies.html

Not exactly what we are talking about, but an obvious sign that there are many exotic diatomic molecules.
 
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  • #5
On the same note as NH4NO3, I found that HOCN can be expressed as two different ions as well: H+ and OCN-. Does that make it an ionic compound then?

I'm confused because the individual atoms are covalently bonded...
 
  • #6
Not necesarilly. Gaseous HCl is covalent, but it easily dissociates into two ions.
 

FAQ: What are the criteria for classifying compounds as ionic?

1. What is an ionic compound?

An ionic compound is a type of chemical compound that is formed when a positively charged ion (cation) and a negatively charged ion (anion) are attracted to each other and bond together through electrostatic forces.

2. How are ionic compounds classified?

Ionic compounds are classified based on the type of ions present and the ratio of cations to anions in the compound. This results in three main categories of ionic compounds: binary, ternary, and polyatomic.

3. What are the properties of ionic compounds?

Ionic compounds have high melting and boiling points, are usually solid at room temperature, and are able to conduct electricity when dissolved in water or in a molten state. They also tend to have crystal lattice structures and are often soluble in polar solvents.

4. How do you name ionic compounds?

Ionic compounds are named by writing the name of the cation first, followed by the name of the anion. The cation's name remains the same as the element, while the anion's name is changed to end in "-ide" for monatomic anions or by following specific naming rules for polyatomic anions.

5. What is the purpose of classifying ionic compounds?

Classifying ionic compounds helps to organize and understand the properties and behavior of these compounds. It also allows for the development of naming conventions and rules for predicting the properties of unknown ionic compounds based on their classification.

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