NEET Structure of Atom — Set 2

Question 1

The angular momentum of an electron in the fifth orbit of $ \text{Be}^{3+} $ is $ 5.275 \times 10^{-34} \, \text{J s} $. What is its radius? ($ h = 6.626 \times 10^{-34} \, \text{J s} $, $ r_1 $ for H = $ 5.29 \times 10^{-11} \, \text{m} $)

Accepted Answer

$ L = \frac{nh}{2\pi} $, $ n = \frac{L \cdot 2\pi}{h} = \frac{5.275 \times 10^{-34} \times 2 \times 3.14}{6.626 \times 10^{-34}} = 5 $. For $ \text{Be}^{3+} $ (Z = 4), $ r_n = \frac{n^2}{Z} r_1 = \frac{5^2}{4} \times 5.29 \times 10^{-11} = 6.25 \times 5.29 \times 10^{-11} = 3.306 \times 10^{-10} \, \text{m} $.

Question 2

How many electrons can occupy the $ 4d $ subshell?

Accepted Answer

For $ l = 2 $ (d subshell), number of orbitals = $ 2l + 1 = 5 $. Electrons = $ 5 \times 2 = 10 $.

Question 3

The uncertainty in momentum of a neutron is $ 5.0 \times 10^{-25} \, \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 5.0 \times 10^{-25}} = 1.055 \times 10^{-10} \, \text{m} $.

NEET Chemistry: Structure of Atom — Practice Set 2

Q1. The angular momentum of an electron in the fifth orbit of \( \text{Be}^{3+} \) is \( 5.275 \times 10^{-34} \, \text{J s} \). What is its radius? (\( h = 6.626 \times 10^{-34} \, \text{J s} \), \( r_1 \) for H = \( 5.29 \times 10^{-11} \, \text{m} \))

Q2. How many electrons can occupy the \( 4d \) subshell?

Q3. The uncertainty in momentum of a neutron is \( 5.0 \times 10^{-25} \, \text{kg m s}^{-1} \). What is the minimum uncertainty in its position? (\( h = 6.626 \times 10^{-34} \, \text{J s} \))

Q4. The radius of the third orbit of a hydrogen atom is \( 4.761 \times 10^{-10} \, \text{m} \). What is the angular momentum of an electron in the fifth orbit? (\( h = 6.626 \times 10^{-34} \, \text{J s} \), \( r_1 \) for H = \( 5.29 \times 10^{-11} \, \text{m} \))

Q5. The work function of a metal is \( 2.5 \, \text{eV} \). What is the maximum wavelength of light that can eject electrons from this metal? (\( h = 6.626 \times 10^{-34} \, \text{J s} \), \( c = 3.0 \times 10^8 \, \text{m s}^{-1} \), \( 1 \, \text{eV} = 1.6 \times 10^{-19} \, \text{J} \))

Q6. The ratio of the angular momentum of an electron in the fifth orbit of \( \text{H} \) to the third orbit of \( \text{He}^+ \) is: (\( h = 6.626 \times 10^{-34} \, \text{J s} \))

Q7. The work function of a metal is \( 3.31 \times 10^{-19} \, \text{J} \). What is the threshold wavelength in nm? (\( h = 6.626 \times 10^{-34} \, \text{J s} \), \( c = 3.0 \times 10^8 \, \text{m s}^{-1} \))

Q8. How many protons, neutrons, and electrons are present in the neutral atom with atomic number 35 and mass number 80?

Q9. A proton and an electron have the same kinetic energy. What is the ratio of their de Broglie wavelengths? (\( m_p = 1.67 \times 10^{-27} \, \text{kg} \), \( m_e = 9.1 \times 10^{-31} \, \text{kg} \))

Q10. What is the frequency of electromagnetic radiation with a wavelength of 600 nm? (Speed of light \( c = 3.0 \times 10^8 \, \text{m s}^{-1} \))