1.Charge on Species (Most Important First)

Species with negative charge are stronger bases than neutral ones.

Example$$OH^- > H_2O$$$$NH_2^- > NH_3$$

Basicity is a measure of how well a compound (a base) shares its lone pair with a proton. The
stronger the base, the better it shares its electrons. Basicity is measured by an equilibrium constant
(the acid dissociation constant, K_a) that indicates the tendency of the conjugate acid of the base to
lose a proton

2. Electronegativity (Across a Period)

If atoms are in the same period, basicity decreases with electronegativity.

Less electronegative atom holds negative charge poorly → stronger base.

3.Hybridization Effect

More s-character stabilizes negative charge, making the base weaker.

4.Resonance

If negative charge is delocalized, the base becomes less basic.

Example:

Acetate ion vs Ethoxide

5.Inductive Effect

Electron-withdrawing groups (–I effect) decrease basicity.

Example

6. Aromaticity

If negative charge contributes to aromatic stabilization, the base becomes weaker.

Example
Cyclopentadienyl anion is stable → weak base.

Quick NEET/JEE Order (Decision Flow)

When comparing bases, check in this order:

1️⃣ Charge
2️⃣ Resonance
3️⃣ Electronegativity
4️⃣ Hybridization
5️⃣ Inductive effect
6️⃣ Aromaticity
7️⃣ Atom size

20 NEET / JEE MCQs – Basic Strength

1

Order of basicity:

CH₃⁻ , NH₂⁻ , OH⁻ , F⁻

A. CH₃⁻ > NH₂⁻ > OH⁻ > F⁻
B. NH₂⁻ > CH₃⁻ > OH⁻ > F⁻
C. OH⁻ > NH₂⁻ > CH₃⁻ > F⁻
D. F⁻ > OH⁻ > NH₂⁻ > CH₃⁻

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2

Which is the strongest base?

A. NH₃
B. CH₃NH₂
C. (CH₃)₂NH
D. C₆H₅NH₂

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3

Order of basicity:

NH₃ , CH₃NH₂ , (CH₃)₂NH , (CH₃)₃N (aqueous)

A. 2° > 1° > 3° > NH₃
B. 3° > 2° > 1° > NH₃
C. NH₃ > 1° > 2° > 3°
D. 1° > 2° > 3° > NH₃

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4

Which is the weakest base?

A. Pyridine
B. Aniline
C. NH₃
D. CH₃NH₂

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5

Correct order of basicity:

NH₂⁻ , OH⁻ , F⁻

A. NH₂⁻ > OH⁻ > F⁻
B. F⁻ > OH⁻ > NH₂⁻
C. OH⁻ > NH₂⁻ > F⁻
D. NH₂⁻ > F⁻ > OH⁻

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6

Which is the strongest base?

A. HC≡C⁻
B. CH₂=CH⁻
C. CH₃⁻
D. C₆H₅⁻

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7

Correct order of basicity:

CH₃NH₂ , C₆H₅NH₂ , NH₃

A. CH₃NH₂ > NH₃ > C₆H₅NH₂
B. NH₃ > CH₃NH₂ > C₆H₅NH₂
C. C₆H₅NH₂ > CH₃NH₂ > NH₃
D. NH₃ > C₆H₅NH₂ > CH₃NH₂

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8

Which compound is most basic?

A. Pyrrole
B. Pyridine
C. Aniline
D. Ammonia

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9

Which is strongest base?

A. CH₃O⁻
B. C₂H₅O⁻
C. OH⁻
D. F⁻

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10

Order of basicity:

sp³ N , sp² N , sp N

A. sp³ > sp² > sp
B. sp > sp² > sp³
C. sp² > sp³ > sp
D. sp³ > sp > sp²

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11

Which is least basic?

A. CH₃NH₂
B. NH₃
C. Aniline
D. (CH₃)₂NH

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12

Which has maximum basicity?

A. NH₂⁻
B. OH⁻
C. H₂O
D. NH₃

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13

Order of basicity:

Pyrrole , Pyridine , Piperidine

A. Piperidine > Pyridine > Pyrrole
B. Pyridine > Piperidine > Pyrrole
C. Pyrrole > Pyridine > Piperidine
D. Pyridine > Pyrrole > Piperidine

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14

Which is stronger base?

A. CH₃NH₂
B. C₆H₅NH₂

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15

Most basic compound:

A. NH₃
B. CH₃NH₂
C. C₂H₅NH₂
D. (CH₃)₂NH

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16

Order of basicity:

NH₃ , PH₃ , AsH₃

A. NH₃ > PH₃ > AsH₃
B. AsH₃ > PH₃ > NH₃
C. PH₃ > NH₃ > AsH₃
D. NH₃ > AsH₃ > PH₃

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17

Which is least basic?

A. Pyrrole
B. Pyridine
C. Piperidine
D. NH₃

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18

Which is strongest base?

A. NH₂⁻
B. CH₃O⁻
C. OH⁻
D. NH₃

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19

Order of basicity:

Aniline , p-methoxyaniline , p-nitroaniline

A. p-OCH₃ > aniline > p-NO₂
B. aniline > p-OCH₃ > p-NO₂
C. p-NO₂ > aniline > p-OCH₃
D. p-OCH₃ > p-NO₂ > aniline

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20

Which is strongest base?

A. NH₃
B. CH₃NH₂
C. (CH₃)₂NH
D. (CH₃)₃N

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Answer Key

1. A
2. C
3. A
4. B
5. A
6. C
7. A
8. B
9. B
10. A
11. C
12. A
13. A
14. A
15. D
16. A
17. A
18. A
19. A
20. C