I have a few questions:

  1. All ionic bond occurs between a metal and a non-metal. Is this true? In the definition of metal and/or non-metal are the metaloids included? In the definition of non-metal are all diatomic and polyatomic non-metals included? Meaning all of those elements form ionic bonds with metals?
  2. When 2 charged molecules form an ionic bond, how is the compound classified?
  3. For ionic compounds formed by only 2 different elements, knowing the metal and the non-metal in question, is it possible to have more than one formula for the compound? I think this is probably possible and maybe even common for the transition metals, because we usually see those roman numerals in their formulae. Am I correct in assume transition metals can form different ionic compounds (meaning different formula) with one same element? If yes, why does that happen?
  4. does item 3 extends to charged molecules?
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    $\begingroup$ Well, this is stark example of too broad. Didn't I already tell you not to ask like this? $\endgroup$
    – Mithoron
    Aug 5 '16 at 11:29
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    $\begingroup$ how can I add something to this question to make it more narrow? I'm beggining to think some people simply don't like me around here. A person managed to answer the question with ease, and even added extra information. $\endgroup$ Aug 6 '16 at 8:59
  • $\begingroup$ Finn this is what you should add as a comment to his answer, not as an edit to your question. Questions without noise and clutter get higher scores too. $\endgroup$
    – M.A.R.
    Aug 6 '16 at 20:31
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    $\begingroup$ You asked four different questions in one post. That's why it's "too broad". $\endgroup$
    – f''
    Aug 8 '16 at 1:46
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    $\begingroup$ @f'' Thank you, I would never have guessed that. The questions are related by a theme, and if someone would bother to read them carefully they would maybe notice that they are put in the form of 4 separate items, but they are all the same thing: I'm trying to make better sense of ionic bonds, and by starting with these questions clarified I can then ask more specific ones. Apparently, people in this community have forgotten what does it mean to "not know" something. $\endgroup$ Aug 8 '16 at 1:52
  1. Not exactly. In ammonium chloride ($\ce{NH4Cl}$), the bond is between a cation ($\ce{NH4^+}$) that has a non metal as its central atom. So the condition that ionic compounds are formed between metal cations and non metal anions is not necessary. Additionally, you will find many organic compounds where the anions or the cations are made up of many atoms, that is the cation itself consists of many atoms, and likewise for the anions. (I guess this was what you meant by charged molecules!). Organic cations (where the cation is not a metal cation) usually have their positive charge centered on a nitrogen atom. Secondly, almost all the non metals are capable of forming ionic bonds, regardless of whether they are diatomic or polyatomic in their elemental state.
  2. It is called an ionic compound.
  3. Yes, in fact transition metal compounds can have different formulae with the same metal and non metal elements! The best example would be $\ce{FeO}$ and $\ce{Fe2O3}$. So why do these different formulae exist? Here is a hint: $\ce{FeO \;=\; Fe^{+2} + O^{-2}}$ and $\ce{Fe2O3\;=\; 2Fe^{+3} + 3O^{-2}}$. Did you spot it? In the first compound, there are $\ce{Fe^{+2}}$ cations, while in the second one, there are $\ce{Fe^{+3}}$ cations! Why does this happen? Well some metal atoms can show two or even more different valencies. For example, once iron has lost the first two electrons, it has the possibility to lose the third electron as well, so it can show both types of positive charge on it, +2 as well as +3. Same is with other cations.
  4. Not sure if anything like that happens. The problem is that generally only metals can lose an extra electron without changing the cation structure, charged molecules may require to change their structure to change the amount of charge they hold. The closest I know is transition metal complexes. The cation does change its compostion in various compounds (as a whole cation), but the central metal atom can remain the same. That is pretty advanced stuff though. You will learn about it in higher classes (in class 12).
  • $\begingroup$ Yes, by "charged molecule" I meant something like $NH_4^+$. Something that has covalent bonds but has a charge. About 2, even if it's a big molecule (covalent bonds) with just one ionic bond somewhere, it is still an ionic compound? About number 3, teachers talk about atoms as if they have a will, they say "the atom wants to have a full outer shell so it gives away/accepts electrons (depending on the atom)". Why transition methods "don't care" about their outer shell so much like the other atoms? About 4, ok, I don't want to deal with nothing extra advanced. $\endgroup$ Aug 6 '16 at 8:55
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    $\begingroup$ About 2, technically maybe yes, but by then we wouldn't bother classifying it like that! For example, charged amino acids may be called ions, but it is uncommon to read about ionic proteins or DNA ion! About 3, you should read about chemical bonding on sites like Wikipedia and chemguide.co.uk. The essence is that all atoms and molecules "want" to decrease their total potential energy. Some have the ability to show different charge on them to suit the situation. But some might do it only because they have no choice. $\endgroup$ Aug 6 '16 at 12:25
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    $\begingroup$ For example, if you were trapped in a castle on a hill. You want to go to the valley, but you do not have enough energy. Then you are stuck there. Now think of your height above sea level as your energy. You cannot lower your energy till someone gives you a boost up the wall! Same is with molecules. Iron may be trapped in +2 state till someone gives it a boost over the wall and sends it to the +3 state! $\endgroup$ Aug 6 '16 at 12:29
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    $\begingroup$ For transition metals, these walls are smaller, and it has a possibility for going lower, so they show multiple oxidation states (look that up). Most of others do not have multiple energy levels to choose from, or have too high walls to climb over. $\endgroup$ Aug 6 '16 at 12:31

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