Inorganic Chemistry Exceptions JEE Main Quiz: Complete Revision Guide

Important Exceptions In Inorganic Chemistry for JEE Main

In this section, you will find the chapter-wise important inorganic chemistry exceptions notes. You can download Inorganic Chemistry Practice Quiz from the download button given below:

Download PDF

Periodic Classification

Chemical Bonding

Chemical Bonding is one of the most important chapters in JEE Main Chemistry. While a lot of questions are based on standard bonding concepts, NCERT exceptions and some special cases are asked again and again.

s-Block Elements

The s-Block Elements chapter has a few high-yield exceptions that are repeatedly asked in JEE Main, kind of again and again, you know.

p-Block Elements

In the p-Block Elements chapter, you’ll find the highest number of NCERT-based exceptions in Inorganic Chemistry. Here are some of the most important and usually asked ones for JEE Main 2027, these are exceptions you really should know.

d- and f-Block Elements

The d- and f-Block Elements chapter includes a bunch of NCERT-based exceptions that are regularly asked in JEE Main. Here are a few of the most important ones you should go through again and revise properly. These are the exceptions that tend to pop up the most, so don’t skip them.

Coordination Compounds

The Coordination Compounds chapter has a bunch of NCERT-based questions that are asked over and over in JEE Main. Usually, the questions revolve around IUPAC naming, magnetic nature, oxidation state, hybridisation, and those special ligands. Below, I’m putting the most essential exceptions to revise again, because questions are asked about them again and again.

Also Read: JEE Main 2027 Chemistry Sample Paper

Inorganic Chemistry Exceptions Quiz for JEE Main

Question 1: Which element has a more negative electron gain enthalpy?

A) Fluorine
B) Chlorine
C) Bromine
D) Iodine

Solution: Answer (B)

Although fluorine is more electronegative, its very small size causes greater electron-electron repulsion. Hence, Cl has a more negative electron gain enthalpy than F.

Question 2: Which pair shows a diagonal relationship?

A) $\mathrm{Na}-\mathrm{Ca}$

B) $\mathrm{Li}-\mathrm{Mg}$

C) $\mathrm{K}-\mathrm{Ca}$

D) $\mathrm{Be}-\mathrm{Si}$

Solution: Answer (B)

Due to similar ionic size and charge density, Li resembles Mg.

Question 3: Which hydrogen halide is the weakest acid?

A) HCl

B) HBr

C) HI

D) HF

Solution: Answer (D)

HF has the strongest H–F bond, making it the weakest acid among hydrogen halides.

Question 4: Which halogen does not form oxyacids?

A) Chlorine

B) Bromine

C) Iodine

D) Fluorine

Solution: Answer (D)

Fluorine cannot exhibit positive oxidation states.

Question 5: Which oxide is neutral?

A) $\mathrm{SO}_2$

B) $\mathrm{CO}_2$

C) NO

D) $\mathrm{P}_2 \mathrm{O}_5$

Solution: Answer (C)

CO, NO and N₂O are neutral oxides.

Question 6: Which element has the electronic configuration $[\mathrm{Ar}] 3 \mathrm{~d}^5 4 \mathrm{~s}^1$?

A) Iron

B) Chromium

C) Copper

D) Manganese

Solution: Answer (B)

Chromium has an exceptional electronic configuration due to the stability of a half-filled d-subshell.

Question 7: Which of the following is not a transition element?

A) Fe

B) Ni

C) Zn

D) Cr

Solution: Answer (C)

Zn and $\mathrm{Zn}^{2+}$ have a completely filled $\mathrm{d}^{10}$ configuration.

Question 8: Which ion is colourless?

A) $\mathrm{Fe}^{3+}$

B) $\mathrm{Cu}^{2+}$

C) $\mathrm{Mn}^{2+}$

D) $\mathrm{Zn}^{2+}$

Solution: Answer (D)

$\mathrm{Zn}^{2+}$ has a $\mathrm{d}^{10}$ configuration, so no d-d transition occurs.

Question 9: The IUPAC name of NH₃ as a ligand is

A) Amino

B) Amide

C) Ammine

D) Ammonia

Solution: Answer (C)

The neutral ligand $\mathrm{NH}_3$ is named ammine.

Question 10: Which is a strong-field ligand?

A) $\mathrm{F}^{-}$

B) $\mathrm{Cl}^{-}$

C) $\mathrm{CN}^{-}$

D) $\mathrm{H}_2 \mathrm{O}$

Solution: Answer (C)

CN⁻ causes the pairing of electrons and forms low-spin complexes.

Question 11: Which of the following elements has a less negative electron gain enthalpy despite having a stable electronic configuration?

A) Sodium
B) Magnesium
C) Chlorine
D) Sulfur

Solution: Answer (B)

Magnesium has the electronic configuration [Ne] 3s². Its 3s subshell is completely filled, so addition of another electron requires entering the higher-energy 3p orbital. Hence, Mg has a positive or nearly zero electron gain enthalpy compared with elements having a greater tendency to accept an electron.

Question 12: Which of the following correctly represents the atomic radius relationship?

A) Ga > Al
B) Ga < Al
C) Ga = Al
D) Ga is much larger than Al

Solution: Answer (B)

Although atomic radius generally increases down a group, gallium has a slightly smaller atomic radius than aluminium. This is due to poor shielding by the intervening 3d electrons, which increases the effective nuclear charge experienced by the outer electrons.

Therefore, Ga < Al

Question 13: Which of the following pairs exhibits a diagonal relationship?

A) Na and Mg
B) Li and Mg
C) K and Mg
D) Na and Ca

Solution: Answer (B)

Lithium and magnesium show a diagonal relationship because they have comparable ionic size, charge density and electronegativity.

Some similarities include the formation of nitrides and relatively covalent compounds.

Therefore, the correct pair is: Li and Mg

Question 14 :Which of the following species has a fractional bond order?

A) N₂
B) O₂
C) O₂⁺
D) F₂

Solution: Answer (C)

According to molecular orbital theory, the bond order of O₂ is 2.

When one electron is removed from O₂ to form $\mathrm{O}_2^{+}$, the electron is removed from an antibonding molecular orbital. Therefore, the bond order increases by 0.5.

Bond order of $\mathrm{O}_2^{+}$ = 2 + 0.5 = 2.5

Hence, $\mathrm{O}_2^{+}$ has a fractional bond order.

Question 15: Which of the following compounds is amphoteric?

A) Na₂O
B) MgO
C) Al₂O₃
D) SO₃

Solution: Answer (C)

Al₂O₃ is an important exception to the general trend of oxide character.

It reacts with both acids and bases. Therefore, it shows amphoteric behaviour.

For example:

$\begin{aligned} & \mathrm{Al}_2 \mathrm{O}_3+6 \mathrm{HCl} \rightarrow 2 \mathrm{AlCl}_3+3 \mathrm{H}_2 \mathrm{O} \\ & \mathrm{Al}_2 \mathrm{O}_3+2 \mathrm{NaOH} \rightarrow 2 \mathrm{NaAlO}_2+\mathrm{H}_2 \mathrm{O}\end{aligned}$

Question 16: Which of the following pairs of elements have nearly identical atomic sizes due to lanthanoid contraction?

A) Na and K
B) Zr and Hf
C) Sc and Y
D) Ti and Zr

Solution: Answer (B)

Lanthanoid contraction causes a gradual decrease in the atomic and ionic radii of lanthanoids due to ineffective shielding by 4f electrons.

As a result, the atomic radii of Zr and Hf become nearly identical, despite Hf being present in a lower period.

Therefore, Zr and Hf show very similar chemical properties.

Question 17: Which lanthanoid commonly exhibits the +4 oxidation state due to additional electronic stability?

A) La
B) Ce
C) Eu
D) Yb

Solution: Answer (B)

Cerium commonly exhibits the +3 oxidation state but can also show the +4 oxidation state.

Ce⁴⁺ has an electronic configuration close to a stable xenon configuration, which provides additional stability.

Therefore, among the given options, Ce is the lanthanoid known for the +4 oxidation state.

Question 18: During the formation of Fe²⁺ from Fe, electrons are removed first from which orbital?

A) 3d
B) 4s
C) 4p
D) 3p

Solution: Answer (B)

The electronic configuration of Fe is:

$\mathrm{Fe}=[\mathrm{Ar}] 3 \mathrm{~d}^6 4 \mathrm{~s}^2$

Although the 4s orbital is filled before the 3d orbital during the Aufbau process, the 4s electrons are removed first during ionisation.

Therefore:

$\begin{aligned} & \mathrm{Fe} \rightarrow \mathrm{Fe}^{2+}+2 \mathrm{e}^{-} \\ & \mathrm{Fe}^{2+}=[\mathrm{Ar}] 3 \mathrm{~d}^6\end{aligned}$

Hence, electrons are removed from the 4s orbital first.

Question 19: What is the correct name of the metal in the anionic complex ion [Fe(CN)₆]⁴⁻?

A) Iron
B) Ferric
C) Ferrate
D) Ferrous

Solution: Answer (C)

When the coordination complex is anionic, the name of the metal is modified by adding the suffix “-ate”.

Therefore:

Iron → ferrate

Thus, $\left[\mathrm{Fe}(\mathrm{CN})_6\right]^4$ contains the metal named ferrate in its IUPAC name.

The complete name is hexacyanidoferrate(II).

Question 20: Which type of complex generally does not show geometrical isomerism?

A) Square planar
B) Octahedral
C) Tetrahedral
D) Both square planar and octahedral

Solution: Answer (C)

Square planar and octahedral complexes can show geometrical isomerism because different spatial arrangements of ligands are possible.

Tetrahedral complexes, however, generally do not show geometrical isomerism because all four positions around the central metal are equivalent.

Therefore, the correct answer is: Tetrahedral complex

Question 21: Which of the following statements is correct?

A. Fluorine has the most negative electron gain enthalpy among all halogens.

B. Chlorine has a more negative electron gain enthalpy than fluorine.

C. Bromine has more negative electron gain enthalpy than chlorine.

D. Iodine has more negative electron gain enthalpy than chlorine.

Solution: Answer (B)

Fluorine has a very small atomic size, so the added electron experiences greater electron–electron repulsion in its compact 2p orbital. Therefore, its electron gain enthalpy is less negative than that of chlorine.

Hence:

$\mathrm{Cl}>\mathrm{F}$

in terms of the magnitude of negative electron gain enthalpy.

Question 22: Which of the following elements does not show variable oxidation states due to its filled d-subshell?

A. Fe

B. Cu

C. Zn

D. Mn

Solution: Answer (C)

Zinc has the electronic configuration:

$\mathrm{Zn}=[A r] 3 d^{10} 4 s^2$

After losing two electrons:

$\mathrm{Zn}^{2+}=[A r] 3 d^{10}$

The d-subshell remains filled. Therefore, Zn predominantly shows the +2 oxidation state and is not considered a transition element.

$\mathrm{Zn}^{2+}: 3 \mathrm{~d}^{10}$

Question 23: Which of the following comparisons of first ionisation enthalpy is correct?

A. IE₁(B) > IE₁(Be)
B. IE₁(Be) > IE₁(B)
C. IE₁(O) > IE₁(N)
D. IE₁(Be) = IE₁(B)

Solution: Answer (B)

The electronic configurations are:

$\begin{gathered}\mathrm{Be}: 1 s^2 2 s^2 \\ \mathrm{~B}: 1 s^2 2 s^2 2 p^1\end{gathered}$

In boron, the electron is removed from the higher-energy 2p orbital, whereas Be has a stable completely filled 2s orbital.

Therefore:

$I E_1(B e)>I E_1(B)$

Therefore, option B is correct.

Question 24: Which of the following ions is expected to be colourless?

A. Ti³⁺
B. Fe³⁺
C. Cu²⁺
D. Zn²⁺

Solution: Answer (D)

The electronic configuration of Zn is:

$\mathrm{Zn}=[A r] 3 d^{10} 4 s^2$

Therefore:

$\mathrm{Zn}^{2+}=[A r] 3 d^{10}$

A filled d-subshell has no possibility of a $\mathbf{d}-\mathbf{d}$ transition. Hence, $\mathrm{Zn}^{2+}$ compounds are generally colourless.

$\mathrm{Zn}^{2+}\left(3 \mathrm{~d}^{10}\right)$

Question 25: Which of the following statements about the inert pair effect is correct?

A. It becomes weaker down the group.
B. It favours higher oxidation states of heavier p-block elements.
C. It favours lower oxidation states of heavier p-block elements.
D. It occurs only in transition elements.

Solution: Answer (C)

The inert pair effect refers to the tendency of the outermost s-electrons to remain less involved in bonding. It becomes more significant as we move down the p-block groups.

As a result, lower oxidation states become more stable in heavier elements.

For example:

$\mathrm{Tl}^{+}>\mathrm{Tl}^{3+}$

in terms of stability.

Thus, the inert pair effect favours the lower oxidation state of heavier p-block elements.

What Is an 'Exception' in JEE Main Inorganic Chemistry?

An Exception is any chemical property, electronic configuration, bond parameter, or reaction that violates standard periodic trends (such as atomic size, ionisation energy, or electronegativity)

Why exceptions occur: They may pop up because of differences in atomic size, electronic configuration, electronegativity, bond strength or sometimes electronic stability too.

Example :

• Ionisation enthalpy: Boron has a lower first ionisation enthalpy than beryllium because its outermost electron has higher energy in the 2p orbital
• Electron gain enthalpy: Chlorine has a more negative electron gain enthalpy than fluorine due to the size of the 2p orbital of fluorine, which experiences greater electron–electron repulsion.

Importance for JEE Main 2027: Understanding exceptions helps to answer the conceptual and multiple-choice questions that test general trends and their limitations.

Common Mistakes Students Make While Learning Inorganic Chemistry Exceptions

Classification of Elements & Periodicity

Treating "smooth trend" as a universal law: Students memorise "IE increases across a period, decreases down a group" and apply it blindly, forgetting that $\mathrm{Be}>\mathrm{B}, \mathrm{Mg}>\mathrm{Al}, \mathrm{N}>\mathrm{O}$, and $\mathrm{P}>\mathrm{S}$ are the rule at those specific points, not the exception to memorise separately. The fix: learn the two triggers $\left(n s^2 \rightarrow n p^1\right.$ and $\left.n p^3 \rightarrow n p^4\right)$ as a pair, not four isolated facts.

Confusing electron gain enthalpy with electronegativity: A huge number of students assume fluorine has the most negative electron gain enthalpy because it's the most electronegative element. These are different properties — electronegativity is about attracting shared electron density in a bond; electron gain enthalpy is about a free gaseous atom accepting an extra electron. Chlorine wins on the second one because F's tiny 2p subshell repels the incoming electron.

p-Block Elements

Assuming every group behaves like row 3 onward : The single biggest error: applying "d orbitals are available for expanded covalency" to period-2 elements. Students write $\mathrm{NF}_5$ or $\mathrm{OF}_6$ as plausible species because they've seen $\mathrm{PF}_5$ and $\mathrm{SF}_6$, forgetting $\mathrm{n}=2$ has no d orbitals at all.

Applying the inert pair effect in the wrong direction: A common slip is expecting the higher oxidation state to be more stable for heavy p-block elements (since that's true earlier in the group), when actually $\mathrm{Tl}^{+}, \mathrm{Pb}^{2+}$, and $\mathrm{Bi}^{3+}$ (two less than the group number) become more stable going down.

d- and f-Block Elements

Not distinguishing d-block from transition elements: Zn, Cd, and Hg are frequently misclassified as ordinary transition metals in options, when by strict definition they're excluded (full $d^{10}$ in all common states).

Assuming all transition metal ions are colored: $\mathrm{Sc}^{3+}, \mathrm{Ti}^{4+}$, and $\mathrm{Cu}^{+}$trip up a lot of students because they're d° or d ${ }^{10}$ - no partially filled d subshell means no d-d transition, hence colourless. Students often forget to check the ion's configuration, not the element's.

Coordination Compounds

The chelate effect confused with bond strength: Students think $\left[\mathrm{Ni}(\mathrm{en})_3\right]^{2+}$ is more stable than $\left[\mathrm{Ni}\left(\mathrm{NH}_3\right)_6\right]^{2+}$ because Ni-N bonds with en are individually stronger. It's actually an entropy effect from releasing more free particles, not bond enthalpy.

Missing that oxidation state can be zero: Metal carbonyls having the metal at 0 oxidation state feel "wrong" to students used to always assigning a positive charge to the central metal, so they misassign oxidation states in $\mathrm{Ni}(\mathrm{CO})_4$-type questions.

Inorganic Chemistry Top Exceptions

Watch this video to know more

Common Traps in Inorganic Chemistry Exceptions

Inorganic chemistry is full of exceptions that can easily confuse students during JEE Main preparation. Use the table below to quickly identify the most common traps and the correct concepts to avoid mistakes in the exam.

Last-Minute 30-Minute Revision Sheet

Use these 30 minutes to quickly revise the most important inorganic chemistry exceptions, unusual trends, and commonly confused concepts. Focus on high-yield facts rather than trying to learn new topics at the last moment.

Best Books of JEE Mains for Inorganic Chemistry

Choosing the right books is kinda essential if you want to master Inorganic Chemistry for JEE Main. Most of the JEE Main questions, in a very straightforward way, are linked to NCERT concepts, facts, and the odd exceptions too. So it makes sense that your preparation should start with NCERT first, then continue towards objective practice books, step by step.

How Much Weightage Do Inorganic Chemistry Exceptions Get in JEE Main?

Inorganic Chemistry exceptions do not have a separate, officially defined weightage in JEE Main. The weightage of inorganic chemistry in JEE Main is approximately 25–30%.

Note: These are approximate chapter-wise planning estimates, not official NTA figures or verified counts of exception-based questions. Actual question distribution varies by examination shift.