Every chemistry student eventually meets a molecule that refuses to play by the octet rule. Nitrogen dioxide (NO2) is that troublemaker. In this guide, you’ll learn exactly how to draw its dot‑and‑cross diagram, why it behaves differently from its ions NO2⁻ and NO2⁺, and what that means for shape and polarity — all with the step‑by‑step detail that makes exam questions click.

4 related posts

Valence electrons in NO2: 17 · Molecular geometry of NO2: bent · Bond angle of NO2: ~134° · Bond angle of NO2⁻: ~115° · Bond angle of NO2⁺: 180° · NO2 radical nature: paramagnetic

Quick snapshot

1Confirmed facts
2What’s unclear
3Timeline signal
  • Lewis dot notation was introduced by Gilbert N. Lewis in 1916, shaping how we represent molecules today (Wikipedia – Lewis structure)
4What’s next

Six key properties in one glance. The table below lays out the basics for neutral NO₂.

Property Value
Molecular formula NO₂
Valence electrons 17
Molecular geometry Bent
Bond angle ~134°
Polarity Polar
Nature Radical

The pattern is clear: NO₂ is an odd‑electron species that forces a bent shape and a net dipole.

How to write Lewis dot structure for NO2?

How many valence electrons does NO2 have?

  • Nitrogen contributes 5 valence electrons; each oxygen contributes 6, giving a total of 5 + 6 + 6 = 17 electrons (University of Maryland – chemistry guide).
  • Because 17 is odd, NO₂ is a radical — it has one unpaired electron. This is the central reason its Lewis structure looks unusual.

What is the Lewis structure of NO2⁻?

  • NO₂⁻ (nitrite ion) has one extra electron, giving 18 valence electrons (University of Maryland – nitrite ion explanation).
  • With an even number, all electrons are paired. The central nitrogen still bonds to two oxygens, but now a lone pair occupies the third position, making the molecule bent with a smaller angle (~115°).

What is the Lewis structure of NO2⁺?

  • NO₂⁺ (nitronium ion) loses one electron compared to neutral NO₂, resulting in 16 valence electrons (Wikipedia – Lewis structure overview).
  • With only 16 electrons, the central nitrogen has no lone pair; the molecule becomes perfectly linear (180°).
The catch

An odd number of valence electrons forces a radical — most textbooks skip this exception, but NO₂ is the classic example. Expect the unpaired electron to sit on nitrogen in the dot‑and‑cross diagram.

The implication: each species in the NO₂ family occupies a distinct electron‑count slot that dictates its shape. That’s why bond angles differ so dramatically.

Is NO2⁻ polar?

What is the molecular geometry of NO2⁻?

  • According to VSEPR theory, NO₂⁻ is classified as AX₂E — two bonding pairs and one lone pair on the central atom. This produces a bent geometry with a bond angle of ~115° (Wikipedia – VSEPR theory).

Is NO2⁻ symmetric?

  • No. The lone pair on nitrogen creates an asymmetric charge distribution. The two N‑O bonds are equivalent in length, but the lone pair’s electron density pushes the bonds closer together, leaving a net dipole moment.

So NO₂⁻ is polar. The negative charge is spread across the molecule, but the shape prevents cancellation of bond dipoles.

Is NO2⁺ polar or nonpolar?

What is the shape of NO2⁺?

  • NO₂⁺ is linear — the nitrogen has no lone pair, so the two oxygens sit at 180° apart. VSEPR classification: AX₂ (Wikipedia – VSEPR theory).

How does the bond angle affect polarity?

  • When a molecule is perfectly linear and both terminal atoms are identical, bond dipoles are equal in magnitude and opposite in direction. They cancel exactly, giving zero net dipole moment.

Therefore NO₂⁺ is nonpolar. The symmetrical charge distribution leaves no permanent dipole.

Why this matters

A student memorising polarity without geometry will get NO₂⁺ wrong. The linear shape is the sole reason it’s nonpolar — remove symmetry and polarity returns.

What is the difference between NO2 and NO2⁻?

Does NO2⁻ exist?

  • Yes. Nitrite (NO₂⁻) is a common anion in chemistry, found in salts like sodium nitrite. It is stable as a closed‑shell species (Wikipedia – Nitrite).

How do their Lewis structures differ?

  • Neutral NO₂ has an unpaired electron on nitrogen (radical). NO₂⁻ has all electrons paired, with a lone pair occupying where the radical electron sits.
  • Both are bent, but the extra electron in NO₂⁻ increases lone‑pair repulsion, reducing the bond angle from ~134° to ~115°.

What are the charges and electron counts?

  • NO₂: neutral, 17 valence electrons, radical.
  • NO₂⁻: −1 charge, 18 valence electrons, closed‑shell.

What this means: the presence of an unpaired electron in NO₂ makes it reactive and paramagnetic, while NO₂⁻ is comparatively stable and diamagnetic.

What are the bond angles of NO2⁺, NO2, and NO2⁻?

Why do the bond angles differ?

  • VSEPR theory predicts geometry based on electron‑pair repulsion. NO₂⁺ has zero lone pairs → linear (180°). NO₂ has one lone pair (and one radical electron that behaves like a lone pair in VSEPR) → bent ~134°. NO₂⁻ has one full lone pair plus a negative charge that increases lone‑pair size → bent ~115° (Wikipedia – VSEPR theory).

How does VSEPR theory explain these angles?

  • AX₂ (NO₂⁺): 180° — no repulsion from lone pairs.
  • AX₂E (NO₂): ~134° — lone pair repulsion compresses bond angle.
  • AX₂E₁ (NO₂⁻): ~115° — lone pair plus negative charge further compresses angle.

The trade‑off: each additional electron on the central atom pushes the bonds closer together, but also changes polarity and stability.

Here’s a direct comparison of the three species side by side.

Property NO₂ NO₂⁻ NO₂⁺
Charge 0 −1 +1
Valence electrons 17 18 16
Geometry Bent Bent Linear
Bond angle ~134° ~115° 180°
Polarity Polar Polar Nonpolar
VSEPR class AX₂E AX₂E₁ AX₂

The pattern is clear: as electron count decreases, the molecule straightens out and polarity disappears.

Step‑by‑Step Guide to Drawing the NO₂ Lewis Structure

  1. Count total valence electrons. N = 5, O × 2 = 12 → total 17 (University of Maryland – chemistry guide).
  2. Place the least electronegative atom in the centre. Nitrogen is less electronegative than oxygen, so N goes in the middle (University of Maryland – chemistry guide).
  3. Draw single bonds from N to each O. This uses 4 electrons (2 bonds × 2 electrons), leaving 13 electrons.
  4. Complete octets of outer atoms (oxygens). Each oxygen gets 6 more electrons (3 lone pairs), using 12 electrons. Now 1 electron remains.
  5. Place the remaining electron on the central N. This makes N have 5 bonds/lone pairs visible? Actually N now has 2 single bonds (4 electrons) plus 1 unpaired electron = 5 electrons around N. That’s an incomplete octet — acceptable for radicals.
  6. Reduce formal charge by forming a double bond. Move one lone pair from one oxygen to form a N=O double bond. Now N has 6 bonding electrons + 1 unpaired = 7 electrons; one oxygen has a double bond, the other a single bond and a lone pair.
  7. Check formal charges. The double‑bonded oxygen: 0. The single‑bonded oxygen: −1. Nitrogen: 0. The sum is −1? Wait, we had 17 electrons, the structure should be neutral. Actually the correct Lewis structure for neutral NO₂ has a formal charge of 0 on N, +0 on one O, and 0 on the other? Standard representation shows one N=O double bond, one N–O single bond, and an unpaired electron on N. Formal charges: doubly bonded O = 0, singly bonded O = −1, N = +1? That sums to 0. Yes, that is the accepted structure. The odd electron is on N.
  8. Draw the dot‑and‑cross diagram. Use crosses for nitrogen electrons, dots for oxygen electrons (or vice versa) to show which atom contributed each electron. The unpaired electron on N is single dot/cross.
  9. Indicate resonance. The double bond can be placed on either oxygen, so draw both resonance structures with a double‑headed arrow.
Bottom line: The catch: unlike most molecules, NO₂ cannot achieve a full octet on N because of the odd electron count. That’s why the radical form is stable at room temperature.

What we know and what remains unclear

Confirmed facts

  • NO₂ has 17 valence electrons (Wikipedia)
  • NO₂ is a radical (University of Maryland)
  • NO₂⁺ is linear (Wikipedia – VSEPR)
  • NO₂⁻ is bent (University of Maryland)
  • NO₂ is polar (Wikipedia – Nitrogen dioxide)

What’s unclear

  • Exact bond angle may vary slightly in different experimental sources
  • Mechanism of NO₂ dimerization under certain conditions is still studied

For the student preparing for exams, the confirmed facts are all you need. The unclear points are fine‑print details for advanced chemistry.

Additional sources

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Frequently asked questions

What is a dot and cross diagram for NO2?

A dot‑and‑cross diagram shows which atom contributes each electron in a covalent bond. For NO₂, it typically displays one N=O double bond, one N–O single bond, and a single unpaired electron on nitrogen. Dots represent oxygen electrons, crosses represent nitrogen electrons (or vice versa).

How many electrons are in the outer shell of nitrogen in NO2?

Nitrogen has 5 valence electrons in its outer shell. In the NO₂ Lewis structure, it uses 4 for bonding (two single bonds, one double bond) and retains 1 as an unpaired electron, giving a total of 7 electrons around N — an incomplete octet.

Is NO2 paramagnetic?

Yes, because it has one unpaired electron. Paramagnetic substances are attracted to magnetic fields. NO₂⁻ and NO₂⁺ are diamagnetic (all electrons paired) (Wikipedia – Nitrogen dioxide).

Can NO2 form a dimer?

Yes, two NO₂ molecules can join to form dinitrogen tetroxide (N₂O₄). This dimerization occurs at lower temperatures and involves pairing the unpaired electrons to form a N–N bond. The dimer is diamagnetic (Wikipedia – Nitrogen dioxide).

What is the hybridization of nitrogen in NO2?

Nitrogen in NO₂ is sp² hybridised. The three sp² orbitals form the two N‑O bonds (sigma bonds) and hold the lone pair (or the radical electron). The unhybridised p orbital contains the unpaired electron and also participates in π bonding.

Why does NO2 have an odd number of valence electrons?

Nitrogen has 5 valence electrons and two oxygen atoms contribute 12, making 17. There is no way to obtain an even total because the sum of the group numbers (5+6+6) is odd. This is a simple consequence of the periodic table.

How does the polarity of NO2 compare to NO2⁻?

Both are polar, but the direction and magnitude of the net dipole differ. NO₂ has a moderate dipole pointing roughly toward the centre of the bent angle. NO₂⁻ has a larger dipole because of its negative charge and more compact angle. NO₂⁺, being linear, has zero dipole.

For the student preparing for chemistry exams, the key takeaway is clear: the number of valence electrons dictates everything — shape, polarity, and stability. NO₂ with its 17 electrons is the odd one out; its radical nature and bent geometry make it a memorable exception to the octet rule. Check out our number to words converter for more step‑by‑step educational guides.