**JEE Main Previous Year Papers Questions With Solutions Chemistry Atomic Structure and Electronic Configuration**

**1.In a hydrogen atom, if energy of an electron in the ground state is 13.6 eV, then that in the 2nd excited state is (2002)**

** 1) 1.51 eV 2) 3.4 eV 3) 6.04 eV 4)13.6 eV**

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**2.**

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**3.Which of the following ions has the maximum magnetic moment. (2002)**

** 1) Mn ^{+2} 2) Fe^{+2} 3) Ti^{+2} 4) Cr^{+2}**

**Ans.**(1) Mn

^{2+}has the maximum number of unpaired electrons (5) and therefore has maximum moment

**4.The number of d-electrons retained in Fe ^{2+ }(At.no. of Fe = 26) ion is (2003)**

**1) 4 2) 5 3) 6 4) 3**

**Ans**.(3) Configuration of Fe

^{+2}= 3d

^{6}.4s°

**5**.

**Ans.**(1) For s-electron, l = 0; Angular momentum=zero

**6.In Bohr series of lines of hydrogen spectrum, the third line from the red end corresponds to which one of the following inter-orbit jumps of the electron for Bohr orbits in an atom of hydrogen (2003)**

** 1) 5 —» 2 2)4 —>1 3) 2—>5 4) 3->2**

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**7.**

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**8.**

**Ans.**(3) For 4f orbital, n= 4 and 1 = 3. Values of m = -3, -2, -1,0, +1, +2, +3. Combination of 1 = 3 m = +1 is the only acceptable option.

**9.Consider the ground state of Cr atom (Z=24).The number of ■electrons with the azimuthal quantum numbers 1 =1 and 2 are respectively**

** 1)12 and 4 2) 16 and 5 (2004)**

** 3) 16 and 4 4) 12 and 5**

**Ans.**(4) Configuration of Cr (Z = 24) is ls^{2}2s^{2}2p^{6}3s^{2}3p^{6}3d^{5}4s*

1=1, denotes p-electrons (2p^{6}, 3p^{6})

1 = 2,’denotes d-electrons (3d^{5})

**10.**

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**11.**

**Ans.**(2) Like +7 state for Mn

**12.In a multi-electron atom, which of the following orbitals described by the three quantum numbers will have the same energy in the absence of magnetic and electric fields?(2005)**

** (a) n = 1,1 = 0, m = 0 (b) n = 2,1 = 0, m = 0**

** (c) n = 2,1 = 1, m = 1 (d) n = 3,1 = 2, m = 1 (e) n = 3,1 = 2, m = 0**

** 1) (a) and (b) 2) (b) and (c)**

** 3) (c) and (d) 4) (d) and (e)**

**Ans.**(4) n is same and orbital is 3d.

**13.Which of the following statements in relation to the hydrogen atom is correct ? (2005)**

** (1)3s orbital is lower in energy than 3p orbital**

** (2)3p orbital is lower in energy than 3d orbital**

** (3)3s and 3p orbitals are of lower energy than 3d orbital**

** (4)3s, 3p and 3d orbitals all have the same energy**

Ans.4) Auf-bau principle is not applicable for H atom

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**16.The “spin-only” magnetic moment [in units of Bohr magneton] of Ni ^{2+} in aqueous solution would be (Atomic number of Ni = 28) (2006)**

**1) 2.84 2) 4.9 3) 0 4) 1.73**

**Ans.**

**17.Which of the following sets of quantum numbers represents the highest energy of an atom ? (2007)**

** (1)n=3, 1=2, m=l, s=+l/2**

** (2)n=3, 1=2, m=l, s=+l/2**

** (3)n=4, 1=0, m=0, s=+l/2**

** (4)n=3, 1=0, m=0, s= +1/2**

**Ans**.(2) Maximum value of (n +1) denotes highest energy of the orbital.

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**23.A gas absorbs a photon of 355 nm and emits**

** at two wavelengths. It one of the emissions is at 680 nm, the other is at (2011)**

** 1) 743 2) 518 3) 1035 4) 325 nm**

**Ans.**

** 24.The electrons identified by quantum numbers n and l (2012)**

** a) n = 4, / = 1 b) n = 4, l = 0**

** c) n = 3, l = 2 d) n = 3, / = 1**

** can be placed in order of increasing energy as**

** l)c<d<b<a 2)d<b<c<a**

** 3)b<d<a<a 4)a<c<b<d**

**Ans.**(2) Greater the (n + /) value, greater is the energy. If (n + l) values are equal, then greater the ‘n’ value greater is the energy.

**Ans.**

**Ans**.(2) 5s^{1} configuration of valence electron.

**27.Which of the following is the energy of a possible excited state of a possible excited state of hydrogen? (2015)**

** 1) +13.6 eV 2) -6.89 eV**

** 3) -3.4 eV 4) +6.8 eV**

**Ans.**

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