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?

Topic 14. Contamination by fertilizers

2 Nitrogen

It is an essential nutrient for plant growth since it constituent all proteins. It is generally absorbed by the roots in NO3- and NH4+. Their assimilation differs because the nitrate ion is found dissolved in the soil solution, while much of the ammonium ion is adsorbed on the clay surfaces. Nitrogen content in soils varies over a broad spectrum, but typical values ​​for the topsoil range from 0.2 to 0.7%. These percentages tend to decrease sharply with depth. Nitrogen tends to increase as soil temperature decreases and atmospheric precipitation increases.

The contributions, transformations, and losses of nitrogen in the soil are outlined in the following cycle. As a result, we can find organic nitrogen (protein, nucleic acids, sugars, and inorganic nitrogen (NH4+, NO3-, NO2-…). Being, generally, organic the most abundant (85 to 95% are typical values).

Assimilable nitrogen comes from various sources and is lost through multiple mechanisms.

The nitrogen cycle is made up of four types of processes:

Molecular nitrogen fixation.

It can be done in different ways.

Symbiotic biological fixation. Certain microorganisms fix the soil’s atmospheric nitrogen that acts symbiotically with plants (preferably legumes act as host plants). 

The mechanism is complex; it is accepted that N2 is transformed to NO3- by the activity of bacteria of the Rhizobium genus and is incorporated into these organisms in the form of amino acids. It is the essential process for plant growth in the absence of fertilizers.

Asymbiotic biological fixation. Certain microorganisms can fix nitrogen without resorting to symbiotic behavior. These are heterotrophic microorganisms against carbon, and they have to take it from sugars, starch, cellulose They are heterotrophic bacteria, photosynthetic bacteria, and blue-green algae.

Non-biological fixation. Nitrogen can be washed directly into the ground by rainwater. It represents a minor pathway against biological fixation.

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

Nitrification. It is the process corresponding to the oxidation of the ammonium ion to nitrate. It develops in two stages. The ammonium ion is oxidized to nitrite (a reaction catalyzed by nitrosobacteria). In the second phase, the nitrite becomes nitrate (by the action of the bacterium Nitrobacter).

Reduction of the nitrate ion. In the absence of oxygen (soils saturated with water), nitrate evolves into ammonium, with nitrate-reductase bacteria intervening in the reducing process, with nitrate acting as an electron acceptor in the oxidation of organic matter.

Denitrification. It is another process of reducing the nitrate ion, but this time to molecular nitrogen. In soils wholly saturated with water, oxygen depletion occurs, and some anaerobic organisms can obtain oxygen from nitrates and nitrites with the simultaneous release of nitrogen and nitrous oxide.

Conversely, soil microorganisms can use mineral nitrogen and transform it into organic nitrogen. This transformation is called biological immobilization.

2.1 Types of nitrogenous fertilizers

The nitrogen added as fertilizer can be urea, NH4+, and NO3-. This nitrogen follows the same reaction patterns as nitrogen released by biochemical processes from plant residues.

Thus, urea is subjected to prior ammonification (formation of NH4+) and nitrification for microorganisms and plants.

Ammonium can be oxidized to NO3- and fixed by solid soil particles or used unchanged by microorganisms and plants.

Nitrates can be taken up directly by microorganisms and plants or lost by volatilization and washing.

2.2 Secondary effects of nitrogen fertilizer

Nutrient contribution, apart from nitrogen, includes S, Mg, Ca, Na and B.

Variation of the soil reaction (acidification or alkalinization)

Increase in soil biological activity with critical indirect effects on the global dynamics of nutrients.

Damage due to salinity and contamination of aquifers, caused by a very high dosage.

Damage caused by impurities and decomposition products.

The side effect, herbicide, and fungicide, of calcium cyanamide.

2.3 Environmental impact of excess nitrogen fertilizers

Nitrate salts are very soluble, so the possibility of anion leaching is high, even more so considering the low adsorption power that most soils have for negatively charged particles.

The most critical environmental problem related to the N cycle is the accumulation of nitrates in the subsoil, which, by leaching, can be incorporated into the groundwater or else be dragged towards the riverbeds and surface reservoirs. In these media, nitrates also act as fertilizers for aquatic vegetation so that, if they become concentrated, they can lead to eutrophication of the environment. In a eutrophic climate, the proliferation of species such as algae and other green plants that cover the surface occurs. 

It results in high oxygen consumption and its reduction in the aquatic environment and hinders the incidence of solar radiation below the surface.

The leaching of nitrates into the subsoil can contaminate underground aquifers, creating severe health problems if water-rich in nitrates is consumed due to its transformation into nitrites by the participation of bacteria in the stomach and urinary bladder. In turn, nitrites are transformed into certain carcinogenic compounds (Nitrosamines), which affect the stomach and liver.

The number of nitrates that leach into the subsoil depends on the rainfall pattern and soil type. Most soils have abundant negatively charged organic and inorganic colloidal particles, which will repel anions, and as a consequence, these soils will easily leach nitrates. On the contrary, many tropical grounds acquire a positive charge and, therefore, show strong nitrate retention.

Soil texture is an essential factor in leaching. The finer the texture, the more retention capacity they will present.

The following figure shows how increasing the fertilizer dose increases the leaching of nitrates.

On the other hand, for the same dose of nitrogen fertilizer, for example, 200 Kg/ha, leaching is more significant when the soil has higher drainage. Likewise, we can evaluate the excess of N produced depending on the amount of fertilizer N applied and soil drainage.

The following figure shows the reaction of crops to nitrogen fertilization and its distribution in the plant and the soil.

To understand this, let’s take a look at the number of atoms in a NO3 molecule and understand how formal charges are calculated. For example, NO−3 is the nitrate ion; it has one nitrogen atom and three oxygen atoms and an overall 1− charge. B = Number of electrons in a covalent bond. -For Nitrogen: From the structure itself, we find a positive charge on Nitrogen, hence it carries a formal charge of +1.

The oxygens which have double-bonds have shared or owned eight electrons, so they are considered neutral. Finally, the single bound oxygen atoms have nine electrons linked with them, and they have a negative charge overall. This means the nitrate ion has an overall charge of -1.

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, giving 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 accommodate 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.


  • NO2 Charge
  • SO4 Charge
  • CO3 Charge
  • NH4 Charge
  • Formal Charge Of NO3-
  • (NO3)2 Charge
  • Agno3 Charge

NO3 Charge