NEET Structure of Atom — Set 6

Question 1

The uncertainty in momentum of an electron is $ 1.0 \times 10^{-24} \, \text{kg m s}^{-1} $. What is the minimum uncertainty in its position? ($ h = 6.626 \times 10^{-34} \, \text{J s} $)

Accepted Answer

$ \Delta x \cdot \Delta p \geq \frac{h}{4\pi} $. $ \Delta x \geq \frac{h}{4\pi \Delta p} = \frac{6.626 \times 10^{-34}}{4 \times 3.14 \times 1.0 \times 10^{-24}} = 5.27 \times 10^{-11} \, \text{m} $.

Question 2

An atom has an electronic configuration of $ 1s^2 2s^2 2p^6 3s^2 3p^6 3d^{10} 4s^1 $. What is its atomic number?

Accepted Answer

Total electrons = 2 + 2 + 6 + 2 + 6 + 10 + 1 = 29. Atomic number = 29.

Question 3

A photon of wavelength 300 nm strikes a metal surface, and the ejected electron has a kinetic energy of $ 2.0 \times 10^{-19} \, \text{J} $. What is the work function of the metal? ($ h = 6.626 \times 10^{-34} \, \text{J s}, c = 3.0 \times 10^8 \, \text{m s}^{-1} $)

Accepted Answer

Photon energy $ E = \frac{hc}{\lambda} = \frac{6.626 \times 10^{-34} \times 3.0 \times 10^8}{300 \times 10^{-9}} = 6.626 \times 10^{-19} \, \text{J} $. Work function $ W_0 = E - KE = 6.626 \times 10^{-19} - 2.0 \times 10^{-19} = 4.626 \times 10^{-19} \, \text{J} $.

NEET Chemistry: Structure of Atom — Practice Set 6

Q1. The uncertainty in momentum of an electron is \( 1.0 \times 10^{-24} \, \text{kg m s}^{-1} \). What is the minimum uncertainty in its position? (\( h = 6.626 \times 10^{-34} \, \text{J s} \))

Q2. An atom has an electronic configuration of \( 1s^2 2s^2 2p^6 3s^2 3p^6 3d^{10} 4s^1 \). What is its atomic number?

Q3. A photon of wavelength 300 nm strikes a metal surface, and the ejected electron has a kinetic energy of \( 2.0 \times 10^{-19} \, \text{J} \). What is the work function of the metal? (\( h = 6.626 \times 10^{-34} \, \text{J s}, c = 3.0 \times 10^8 \, \text{m s}^{-1} \))

Q4. An atom has the electronic configuration \( 1s^2 2s^2 2p^6 3s^2 3p^5 \). What is its atomic number?

Q5. The wavenumber of the second line in the Paschen series of a hydrogen atom is: (\( R_H = 1.097 \times 10^7 \, \text{m}^{-1} \))

Q6. The number of spectral lines produced when an electron falls from \( n = 8 \) to \( n = 5 \) in a hydrogen atom is:

Q7. In a hydrogen atom, the energy of an electron in the first orbit is \(-2.18 \times 10^{-18} \, \text{J}\). What is the energy of the electron in the third orbit?

Q8. The kinetic energy of a photoelectron is \( 3.0 \times 10^{-19} \, \text{J} \) when irradiated with light of frequency \( 8.0 \times 10^{14} \, \text{Hz} \). What is the threshold frequency of the metal? (\( h = 6.626 \times 10^{-34} \, \text{J s} \))

Q9. What is the maximum number of orbitals in the \( n = 2 \) energy level?

Q10. How many possible sets of quantum numbers (\( n, l, m_l, m_s \)) are there for electrons in the \( n = 3 \) energy level?