Why does NO3 have a charge of -1? Shouldn’t the charges add up to -9?

NO3 Charge

Why does NO3 have a charge of -1? Shouldn’t the charges add up to -9?

A formal charge, or chemical charge, is the charge that an atom has in a molecule, assuming that the electrons found in chemical bonds are all shared equally among the atoms that make up the molecule. This means that relative electronegativity is not a factor.

In order to calculate a formal charge, electrons are assigned to individual atoms in the molecule according to two different rules: bond electrons must be distributed equally among the different bonded atoms, and unbound electrons are considered to be part of the atom where they are.

Nitrate, chemical formula NO3, has a chemical charge of -1. Ionic nitrates have a negative formal charge. You might be wondering why this is the case. Why is the full charge of the N03 -9 not complete?

To understand this, let’s take a look at the number of atoms in a NO3 molecule and understand how formal charges are calculated.

Why does NO3 have a charge of -1? Shouldn’t the charges add up to -9?

Yes, there is some logic behind it, but your excellent question shows that the answer is not obvious.

Looking at oxygen first, each oxygen atom has 2 electrons in its inner shell, and 6 in its second shell. For quantum mechanical reasons, oxygen has ‘room’ for two more electrons in its second shell, because the second shell has room for 8 electrons.

(This is partly because the second shell is close to its positively charged nucleus, and so we can informally think of oxygen as ‘wanting’ two electrons. Technically, we say that oxygen is highly electronegative).

So three oxygen atoms ‘want’ 6 electrons as you indicated in your question.

Now comes the harder part. Nitrogen has a total of 7 electrons – two in its inner shell and 5 in its second shell. So by the reasoning above, you’d think that nitrogen has room for 3 more electrons in its second shell. And indeed it does.

And some compounds, such as lithium nitride, Li3N, follow this pattern. (The nitrogen takes an electron from each of the three lithium atoms to complete its outer shell).

But now consider this. With 5 electrons in nitrogen’s outer shell, it can also be ‘happy’ by giving away these 5 electrons, leaving only its two inner shell electrons.

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After all, that’s the sort of thing sodium atoms do when they react with chlorine atoms. A sodium atom gives its single outer shell electron to a chlorine atom, forming table salt.

So nitrogen gives away its five outer shell electrons to the three oxygen atoms because the oxygen atoms pull more strongly on the nitrogen’s outer electrons than nitrogen’s own nucleus does.

Now we’re getting close to the answer to your question. The nitrogen atom loses 5 electrons to the three oxygen atoms. But these three oxygen atoms want 6 electrons. So there’s still a strong need for one last electron.

And so when, for example, sodium forms the compound sodium nitrate, NaNO3, the single outer-shell sodium electron transfers over to the NO3, making it a nitrate ion, giving it a -1 charge. (And to keep things balanced this also forms a sodium ion with a +1 charge).

Why does nitrate (NO3) have a -1 charge if a nitride ion has a charge of -3?

Because there is no reason why the monoatomic ion of an element has the same charge as its oxyanions.

The nitrate ion is held together by covalent bonds, but if we look at the oxidation states of the atoms in it (which is a way of accounting for electrons which are sort of based on an “all bonds” premise are ionic ”, we would find that because oxygen is more electronegative (grabs electrons more tightly) than nitrogen, nitrogen has lost its 5 outer electrons, giving it an oxidation state of +5.

Oxygens tend to gain 2 electrons, given them a full outer shell and oxidation state of -2, so the three oxygens gain a total of 6 electrons.

They could only get 5 of the nitrogen, which meant that an electron had to come from somewhere else, which gave the overall ion a charge of -1.

Why Does NO2 Carry A Negative Charge?

TO UNDERSTAND that why it carries a negative charge… just look up at the following points


  • N nitrogen has a valency of -3 i.e., its needs 3 electrons to complete its octet.
  • Now oxygen has a valency of -2 it needs only 2 electrons to complete its octet.
  • Thwh ASSUMING… they are held by a covalent bond in which they share pairs of electrons…(even though there is no covalent bond is there)
  • NOW oxygen needs 2 pairs whereas nitrogen needs 3 pairs…
  • Then both can have only 2 pairs of shared electrons…
  • Now nitrogen is lacking one bond .and it needs it.
  • This net charge of NO2 is -1 so that it can acquire one more pair to become stable.

What is the oxidation number of NO3 and NO?

In a molecule, the oxidation number is equal to the charge of the molecule. So zero is the answer for the two you listed. The difference is in the nitrogen atoms in each, the oxidation number is different.

In NO with oxygen having -2 as the oxidation number (one of the main oxidation numbering rules), nitrogen should have +2 as the oxidation number. For NO_3, you have 3 * -2 = -6 oxidation of all oxygen, so your nitrogen is going to have an oxidation number of +6.

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Which is more stable, Fe2+ or Fe3+?

The underlying principle involved in this is “ half-filled and fully-filled orbitals are extra stable .” the d subshell has five orbitals, which can acomodate a total of 10 electrons.

Fe3+Fe3+ (3d5)(3d5)has half filled orbitals which provide extra stability to it because of symmetrical configuration. While Fe2+(3d6)Fe2+(3d6) has one electron more than the symmetrical arrangement. That is whyFe3+Fe3+ is more stable than Fe2+Fe2+ .

What is the charge of nitride?

The magnitude of the negative charge is given by the difference between the number of protons and the number of electrons. In this case, each extra electron will add a charge of 1− to the ion. Therefore, the overall charge on the nitride anion is (3−).

How is NO3 formed?

The nitrate ion is formed by the loss of the hydrogen ion, and so its structure is: Around the central nitrogen there are 4 pairs of shared electrons and no remaining lone pair. The original lone pair has now become a bonding pair. Two of those pairs make up a double bond.


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