Structure of Atom JEE Main previous year questions with solutions

5 solved JEE Main questions on Structure of Atom, free to read — no sign-in needed. The full chapter has 249 questions; sign in to attempt the remaining 244 in the exam simulator.

1. Q1JEE Main 2026 (04 Apr, Shift 1)Atomic Mass and Atomic Size
   A monoatomic anion $(A^-)$ has $45$ neutrons and $36$ electrons. Atomic mass, group in the periodic table and physical state at room temperature of the element $(A)$ respectively are
   1. A.$80, 17$, liquid
   2. B.$81, 16$, solid
   3. C.$80, 16$, gas
   4. D.$81, 15$, gas
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   Answer: (A)

   Number of electrons in $A^{-}$ is $36$. Number of electrons in neutral atom $A = 36 - 1 = 35$. Atomic number of $A = 35$. Number of protons in $A = 35$. Atomic mass of $A = \text{Number of protons} + \text{Number of neutrons} = 35 + 45 = 80$. The element with atomic number $35$ is Bromine ($\text{Br}$). Bromine belongs to Group $17$ of the periodic table. The physical state of Bromine at room temperature is liquid. Answer: $80, 17$, liquid
2. Q2JEE Main 2025 (02 Apr, Shift 1)Bohr's model
   According to Bohr's model of hydrogen atom, which of the following statement is incorrect?
   1. A.Radius of $3^{\text {rd }}$ orbit is nine times larger than that of $1^{\text {st }}$ orbit.
   2. B.Radius of $8^{\text {th }}$ orbit is four times larger than that of $4^{\text {th }}$ orbit.
   3. C.Radius of $6^{\text {th }}$ orbit is three time larger than that of $4^{\text {th }}$ orbit.
   4. D.Radius of $4^{\text {th }}$ orbit is four times larger than that of $2^{\text {nd }}$ orbit.
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   Answer: (C)

   $\mathrm{r} \propto \mathrm{n}^2$ (1) $\frac{\mathrm{r}_3}{\mathrm{r}_1}=\frac{9}{1}$ (2) $\frac{\mathrm{r}_8}{\mathrm{r}_4}=\frac{64}{16}=4$ (3) $\frac{\mathrm{r}_6}{\mathrm{r}_4}=\left(\frac{6}{4}\right)^2=\frac{9}{4}$ (4) $\frac{\mathrm{r}_4}{\mathrm{r}_2}=\left(\frac{4}{2}\right)^2=4$
3. Q3JEE Main 2024 (04 Apr, Shift 2)Atomic Models
   Choose the Incorrect Statement about Dalton's Atomic Theory
   1. A.chemical reactions involve reorganization of atoms
   2. B.Matter consists of indivisible atoms.
   3. C.Compounds are formed when atoms of different elements combine in any ratio.
   4. D.Compounds are formed when atoms of different elements combine in any ratio. All the atoms of a given element have identical properties including identical mass.
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   Answer: (C)

   In compound atoms of different elements combine in fixed ratio by mass.
4. Q4JEE Main 2023 (12 Apr, Shift 1)Dual Behaviour of Matter and Heisenberg Uncertainty Principle
   Values of work function $({W}_{0})$ for a few metals are given below Metal $Li$ $Na$ $K$ $Mg$ $Cu$ $Ag$ $\dfrac{{W}_{0}}{eV}$ $2.42$ $2.3$ $2.25$ $3.7$ $4.8$ $4.3$ The number of metals which will show photoelectric effect when light of wavelength $400nm$ falls on it is _____ Given: $h=6.6\times {10}^{–34}Js$ $c=3\times {10}^{8}{ms}^{–1}$ $e=1.6\times {10}^{–19}C$
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   Answer: 3

   The minimum amount of energy necessary to start the emission of electrons from a metal's surface is known as its work function. The work function is the minimum amount of energy required to remove an electron from a metal's surface to infinity. Energy of incident photon $=\dfrac{hc}{\lambda }$ $=\dfrac{6.6\times {10}^{-34}\times 3\times {10}^{8}}{400\times {10}^{-9}}J$ $=\dfrac{6.6\times {10}^{-34}\times 3\times {10}^{8}}{400\times {10}^{-9}\times 1.6\times {10}^{-9}}eV$ $=3.1eV$ If radiation energy is greater than work function of metal, then metal show photo electric effect. $∴Li,Na$ and $K$ will show photoelectric effect.
5. Q5JEE Main 2022 (29 Jul, Shift 2)Electronic configuration
   Given below are the quantum numbers for $4$ electrons. A. $n=3,l=2,{m}_{1}=1,{m}_{s}=+\dfrac{1}{2}$ B. $n=4,l=1,{m}_{1}=0,{m}_{s}=+\dfrac{1}{2}$ C. $n=4,l=2,{m}_{1}=-2,{m}_{s}=-\dfrac{1}{2}$ D. $n=3,l=1,{m}_{1}=-1,{m}_{s}=+\dfrac{1}{2}$ The correct order of increasing energy is
   1. A.$D\lt B\lt A\lt C$
   2. B.$D\lt A\lt B\lt C$
   3. C.$B\lt D\lt A\lt C$
   4. D.$B\lt D\lt C\lt A$
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   Answer: (B)

   Energy order of sub-shell decided by $\left(n+l\right)$ value. Greater the $\left(n+l\right)$ value of a sub-shell greater is its energy. If two sub-shells have same $\left(n+l\right)$ values the orbital with greater principal quantum number has greater energy $A\Rightarrow 3d\Rightarrow \left(n+l\right)=3+2=5$ $B\Rightarrow 4p\Rightarrow n+l=4+1=5$ $C\Rightarrow 4d\Rightarrow n+l=4+2=6$ $D\Rightarrow 3s\Rightarrow \left(n+l\right)=3+0=3$ $D\lt A\lt B\lt C$