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Is sodium nitrate a covalent or ionic compound? This is a test question. I put the answer ionic compound but my teacher says that statement is false because it is only partially ionic as there is covalent bond between nitrogen and oxygen in the nitrate ion. Is that true?

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    $\begingroup$ Life is full of inadequate test questions. Bear with it. Sodium nitrate is a completely ionic, and at the same time a covalent compound, like a great deal of other salts. $\endgroup$ – Ivan Neretin May 23 '17 at 8:44
  • $\begingroup$ So what will the answer be? $\endgroup$ – Tumbalalaika May 23 '17 at 8:52
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    $\begingroup$ The answer will be whatever your teacher wants it to be, as is customary with inadequate questions. $\endgroup$ – Ivan Neretin May 23 '17 at 8:54
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    $\begingroup$ Yup, stupid test question. $\endgroup$ – Pritt Balagopal May 23 '17 at 9:25
  • $\begingroup$ Is the test's language English? There might be subtle differences in terminology that may apply if you're translating - you might want to include the original text if that's the case. Though I have to admit I can't imagine how you could possibly give a better answer than "neither" or "both" - I certainly wouldn't say that it's fine to call it "covalent" while it's not fine to call it "ionic". $\endgroup$ – Luaan May 23 '17 at 13:38
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Bonds are usually used to describe how electrons are shared. "Partially ionic bonds" are polar covalent bonds. Which is not the same as saying that a compound has different types of bonds in the whole compound. I think that your teacher gave you a bad question and a bad answer. If the question had asked whether all the bonds in sodium nitrate are ionic, then it would be a different story.

However, it is true that the bonds between the nitrogen and oxygen are covalent. Nevertheless, stating that sodium nitrate is ionic shouldn't be wrong.

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If you are asked on a test "Is sodium nitrate ionic or covalent?", say "ionic" and if given the opportunity, justify your answer with electrical conductivity of molten sodium nitrate and aqueous sodium nitrate.

Chemistry: The Molecular Science :

Polyatomic Ions
In addition to atomic ions such as Na+ and Cl-, ionic compounds often contain groups of atoms with a net electrical charge. Sodium nitrate is an example of an ionic substance that contains such a group.

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The answer your teacher seems to have been looking for was to specify that the the sodium-nitrate bond is ionic and nitrate's nitrogen-oxygen bond is covalent.

This is under the assumption that the question was not multiple choice but was short answer. You may be able to contest the marking, but I wouldn't expect a change.

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    $\begingroup$ Yup, No changes. I argued but she was very rigid holding on to her answer. But the point is I got to know the true answer and explanation. $\endgroup$ – Tumbalalaika May 27 '17 at 13:03

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