NEET ChemistryUpdated 19 Oct 2026

Structure of an Atom: NEET PYQs and weightage

Structure of an Atom carries 3.4 of 100 Chemistry marks in NEET by past-paper share: 24 of the 707 tagged NEET Chemistry PYQs in the ViJEEta bank (NEET 2013–2026). It ranks 16 of 26 Chemistry chapters.

Take the 25-question Structure of an Atom test Formula sheet ↓All NEET Chemistry chapters

3.4/100 Weight in Chemistry

Exam importance (3/5, by past-paper share)

24 NEET PYQs

435 Practice questions

409 With measured difficulty

How the weight is computed: this chapter's tagged NEET PYQs divided by all tagged NEET Chemistry PYQs in the bank (24 of 707), times 100, with repeated questions counted once. The bank does not store the year of each NEET question, so none is printed. Computed from the bank at build time. Updated 19 Oct 2026.

Structure of an Atom: formula sheet for NEET

14 formulas, each with when to use it. Copy it onto one page of your notebook: that page is this chapter's handbook.

Bohr energy (H and H-like ions)
$E_{n} = - 2.18 \times 1 0^{- 18} \times \frac{Z ^{2}}{n ^{2}} J per atom$
Use it when: you need the energy of an electron in orbit $n$ of H, $H e^{+}$ , $L i^{2 +}$ , $B e^{3 +}$ (ground state $n = 1$ )
Bohr radius
$r_{n} = 52.9 \times \frac{n ^{2}}{Z} pm$
Use it when: you need the size of orbit $n$ ; for H, $n = 1$ gives $52.9 pm$
Transition energy
$Δ E = 2.18 \times 1 0^{- 18} (\frac{1}{n _{i}^{2}} - \frac{1}{n _{f}^{2}}) J$
$ν = \frac{∣Δ E ∣}{h}$
Use it when: an electron jumps orbits in a hydrogen atom; $Δ E$ is negative for emission ( $n_{i} > n_{f}$ ) and positive for absorption
Rydberg (hydrogen lines)
$\overset{ν}{ˉ} = \frac{1}{λ} = 109677 (\frac{1}{n _{1}^{2}} - \frac{1}{n _{2}^{2}}) cm^{- 1} (n_{2} > n_{1})$
Use it when: finding a line's wavelength. $n_{1} = 1$ Lyman (UV), $2$ Balmer (visible), $3$ Paschen, $4$ Brackett, $5$ Pfund (IR)
Photon energy
$E = h ν = \frac{h c}{λ}$
$h = 6.626 \times 1 0^{- 34} J s$
$c = 3.0 \times 1 0^{8} m s^{- 1}$
Use it when: converting between energy and wavelength or frequency; put $λ$ in metres, not nm
Wave relation
$c = ν λ$
$\overset{ν}{ˉ} = \frac{1}{λ}$
Use it when: switching between frequency, wavelength and wavenumber ( $\overset{ν}{ˉ}$ is usually given in $cm^{- 1}$ )
Photoelectric (Einstein)
$\frac{1}{2} m_{e} v^{2} = h ν - h ν_{0} = h ν - W_{0}$
Use it when: finding the KE of an ejected electron or the work function; no emission if $ν < ν_{0}$
de Broglie
$λ = \frac{h}{m v} = \frac{h}{p} = \frac{h}{2 m \cdot KE}$
Use it when: finding the wavelength of a moving particle; $m$ in kg, KE in J
Heisenberg
$Δ x \cdot Δ p \geq \frac{h}{4 π}$
$Δ x \cdot m Δ v \geq \frac{h}{4 π}$
Use it when: given an uncertainty in position, you must find the uncertainty in velocity, or the reverse
Bohr angular momentum
$m_{e} v r = \frac{nh}{2 π}$
Use it when: asked for the angular momentum in orbit $n$ , or which orbits are allowed
Quantum number limits
$l = 0 to n - 1$
$m_{l} = - l to + l (2 l + 1 values)$
$m_{s} = + \frac{1}{2} or - \frac{1}{2}$
Use it when: checking whether a set of quantum numbers is allowed, or counting orbitals in a subshell (s 1, p 3, d 5, f 7)
Orbitals and electrons in shell n
$orbitals = n^{2}$
$max electrons = 2 n^{2} (2 per orbital, opposite spins)$
Use it when: counting orbitals or electrons for a given $n$
Nodes
$radial = n - l - 1$
$angular = l$
$total = n - 1$
Use it when: counting nodes in an orbital (e.g. 3p has 1 radial and 1 angular node)
Photon count
$number of photons = \frac{energy delivered}{h c / λ} = \frac{P \times t}{h c / λ}$
Use it when: a bulb or laser of power $P$ (in $J s^{- 1}$ ) is given; multiply the energy of one photon ( $h c / λ$ ) by $N_{A} = 6.022 \times 1 0^{23} mol^{- 1}$ for the energy of one mole of photons

Trap

Students forget Z for He⁺, Li²⁺ and Be³⁺. Energy scales as Z²/n², but the radius scales as n²/Z, so Z does not enter both the same way.

How does NEET ask Structure of an Atom?

8 real previous-year questions from this chapter, as printed in the paper, each with its worked solution. Answer the first one here with no sign-in.

Q1ChemistryNEET UG PYQBohr's Model of an Atom

Try right here · No sign-in

Based on equation

E = - 2.178 \times 1 0^{- 18} (\frac{Z ^{2}}{n ^{2}})

certain conclusions are written? Which of them is not correct.

Answer key (D) & worked solution

Correct answer: Option D

The electrons closer to the nucleus are more strongly bonded.

Q2ChemistryNEET UG PYQQuantum Numbers

The relation between n

_{m}

, (n

_{m}

= the number of permissible values of magnetic quantum number (m)) for a given value of azimuthal quantum number (l),is

l = 2 n_{m} + 1

n_{m} = 2 l^{2} + 1

n_{m} = l + 2

l = \frac{n _{m} - 1}{2}

Answer key (D) & worked solution

Correct answer: Option D

Number of permissible values of magnetic quantum number for a given value of azimuthal quantum (ℓ) $\begin{gathered} \Rightarrow {n_m} = 2\ell + 1 \\ \Rightarrow \ell = \frac{{{n_m} - 1}}{2} \\ \end{gathered} $

Q3ChemistryNEET UG PYQCharacteristics of Wave

The value of Planck’s constant is 6.63 × 10

^{- 34}

Js. The speed of light is 3 × 10

^{17}

nm s

^{- 1}

. Which value is closest to the wavelength in nanometer of a quantum of light with frequency of 6 × 10

^{15}

^{- 1}

A10

B25

C50

D75

Answer key (C) & worked solution

Correct answer: Option C

we knowc =

λ ν

λ = \frac{c}{v} = \frac{3 \times 10 ^{17} nm s ^{- 1}}{6 \times 10 ^{15} s ^{- 1}} = 50 nm

Q4ChemistryNEET UG PYQQuantum Numbers

What is the maximum number of orbitals that can be identified with the following quantum numbers? n = 3, l = 1, m

_{1}

= 0

Answer key (C) & worked solution

Correct answer: Option C

l = 1 & m = 0 ⇒ p

_{z}

= orbital

Q5ChemistryNEET UG PYQElectronic Configuration

^{2 +}

is isoelectronic with which of the following ions?

AH+

BLi+

CNa+

DMg2+

Answer key (B) & worked solution

Correct answer: Option B

^{2 +}

has 2e

^{-}

and Li

^{+}

also has 2e

^{-}

Q6ChemistryNEET UG PYQBohr's Model of an Atom

The energy of an electron in the ground state (n = 1) for He

^{+}

ion is –x J, then that for an electron in n = 2 state for Be

^{3 +}

ion in J is

- \frac{x}{9}

B–4x

- \frac{4}{9} x

D–x

Answer key (D) & worked solution

Correct answer: Option D

E_{n} \propto \frac{Z ^{2}}{n ^{2}}

In case He

^{+}

z = 2, n = 1 = –x J In case Be

^{+ 3}

z = 4, n = 2 = –x J

Q7ChemistryNEET UG PYQBohr's Model of an Atom

Energy and radius of Bohr Orbit of He

^{+}

and Li

^{2 +}

are [Given R

_{H}

= 2.18 × 10–18 J, a

_{0}

= 52.9 pm]

_{n}

(Li

^{2 +}

) = –19.62 × 10–16 J; r

_{n}

(Li

^{2 +}

) = 17.6 pm, E

_{n}

(He

^{+}

) = 8.72 × 10–16 J, r

_{n}

(He

^{+}

) = 26.4 pm

_{n}

(Li

^{2 +}

) = –8.72 × 10–16 J; r

_{n}

(Li

^{2 +}

) = 17.6 pm, E

_{n}

(He

^{+}

) = –19.62 × 10–16 J, r

_{n}

(He

^{+}

) = 17.6 pm

_{n}

(Li

^{2 +}

) = –19.62 × 10–1

^{8}

J; r

_{n}

(Li

^{2 +}

) = 17.6 pm, E

_{n}

(He

^{+}

) = –8.72 × 10–1

^{8}

J, r

_{n}

(He

^{+}

) = 26.4 pm

_{n}

(Li

^{2 +}

) = –8.72 × 10–1

^{8}

J; r

_{n}

(Li

^{2 +}

) = 26.4 pm, E

_{n}

(He

^{+}

) = –19.62 × 10–1

^{8}

J, r

_{n}

(He

^{+}

) = 17.6 pm

Answer key (C) & worked solution

Correct answer: Option C

_{n}

(Li

^{2 +}

) = –19.62 × 10–1

^{8}

J; r

_{n}

(Li

^{2 +}

) = 17.6 pm, E

_{n}

(He

^{+}

) = –8.72 × 10–1

^{8}

J, r

_{n}

(He

^{+}

) = 26.4 pm

Q8ChemistryNEET UG PYQQuantum Numbers

The angular momentum of electron in ‘d’ orbital is equal to:

ℏ

6

ℏ

2

ℏ

3

ℏ

Answer key (B) & worked solution

Correct answer: Option B

Angular momentum of electron in ‘d’ orbital

= ℓ (ℓ + 1)

ℏ

= 2 (2 + 1)

ℏ

6

ℏ

Which topics in Structure of an Atom carry the most questions?

The 12 busiest of 15 topics, by tagged PYQs, then practice questions. Counted from the bank. Updated 19 Oct 2026.

Topic	PYQs	Practice questions
Quantum Numbers	11	100
Bohr's Model of an Atom	4	80
Electronic Configuration	4	61
Subatomic Particles	2	36
Planck's Quantum Theory	1	16
Characteristics of Wave	1	10
Schrodinger's Wave Equation	1	6
Hydrogen Spectra	0	30
Dual Nature of Particle	0	26
Heisenberg's Uncertainty Principle	0	18
Particle Nature of Electromagnetic Radiations	0	18
Electromagnetic Spectrum	0	11

Why does Structure of an Atom show "–" until you answer 3 questions?

Unknown is not zero. Until you answer at least 3 graded questions in Structure of an Atom, ViJEEta shows – instead of a zero or a 50% default. Book exercises can raise chapter mastery up to 0.60, adaptive practice up to 0.75, and only a timed chapter test or mock can certify 0.80 and above.

How ViJEEta scores you

What happens when you test Structure of an Atom?

Every chapter test is 25 questions. It starts at moderate difficulty and adapts after each saved answer. If you open a solution before answering, that attempt earns no credit, so your mastery stays honest.

Start the Structure of an Atom test

Chapters either side of Structure of an Atom by weight

Ionic Equilibrium Weight 3.4/100 Some Basic Concepts of Chemistry Weight 3.4/100 Classification of Elements and Periodicity Weight 3.1/100 Organic Chemistry: Some Basic Principles and Techniques Weight 3.0/100

Structure of an Atom: NEET PYQs and weightage

Structure of an Atom: formula sheet for NEET

Bohr energy (H and H-like ions)

Bohr radius

Transition energy

Rydberg (hydrogen lines)

Photon energy

Wave relation

Photoelectric (Einstein)

de Broglie

Heisenberg

Bohr angular momentum

Quantum number limits

Orbitals and electrons in shell n

Nodes

Photon count

How does NEET ask Structure of an Atom?

Which topics in Structure of an Atom carry the most questions?

Why does Structure of an Atom show "–" until you answer 3 questions?

What happens when you test Structure of an Atom?

Chapters either side of Structure of an Atom by weight