Answers Assignment - 1 Structure of Atom | Class 11th

Answers Assignment – 1

Structure of Atom

Ans 1. Hydrogen atom. It consists of only one proton.

Ans 2. Wave number = 1/ wavelength   

Wavelength = 5800 A⁰= 5800 x 10^-10 m  

Wave number = 1/5800 x 10^-10 m = 1.72 x 10⁶ m^-1

Ans 3. n=2 and l= 1

Ans 4. 1p and 3f are not possible.

Ans 5. 1s² 2s² 2p⁶ 3s² 3p⁶ 3d⁵ 4s¹

Ans 6. velocity of light = frequency x wavelength. Frequency and wavelength are inversely proportional to each other.

Ans 7. No two electrons in an atom can have the same set of four quantum numbers or an orbital can have maximum two electrons and these must have opposite spin.

Ans 8. There is a very small heavy body present within the atom.

Ans 9. The smallest packet of energy of any radiation is called a quantum whereas that of light is called photon.

Ans 10. (a) 1s (b) 3p (c)4d (d) 4f

Ans 11. (a) 16 electrons  (b) 2 electrons.

Ans 12. Mass number = 81, i.e., p + n = 81  

If protons = x, then neutrons = x + 31.7 × x = 1.317 x

        100  

x+1.317x = 81 or 2.317x = 81     x=35  

Thus proton = 35, i.e., atomic no. = 35   Hence symbol is ⁸¹₃₅Br

Ans 13. (i) E_n = -2.18 × 10^-18/ n²           E₅ = -2.18 × 10^-18/ 5²   = -8.72 × 10^-20 J   

(ii) For H atom, r_n= 0.529 × n²         r₅ = 0.529 × 5² = 13.225 A⁰= 1.3225 nm

Ans 14. For 3p orbitals, n=3, l= 1 

Number of angular nodes = l= 1 

Number of radial nodes = n-l-1 = 3-1-1= 1