NEET Structure of Atom — Set 14

Question 1

The electronic configuration of an element is $ 1s^2 2s^2 2p^6 3s^2 3p^3 $. What is the atomic number of this element?

Accepted Answer

Total electrons = 2 + 2 + 6 + 2 + 3 = 15. Atomic number = 15.

Question 2

An element has 20 protons and 20 neutrons. What is its atomic mass number?

Accepted Answer

Mass number $ A = $ protons + neutrons = 20 + 20 = 40.

Question 3

The energy required to excite an electron from $ n = 2 $ to $ n = 5 $ in a hydrogen atom is $ 4.896 \times 10^{-19} \, \text{J} $. What is the wavelength of the absorbed photon? ($ h = 6.626 \times 10^{-34} \, \text{J s} $, $ c = 3.0 \times 10^8 \, \text{m s}^{-1} $)

Accepted Answer

$ \lambda = \frac{hc}{\Delta E} = \frac{6.626 \times 10^{-34} \times 3.0 \times 10^8}{4.896 \times 10^{-19}} = 4.061 \times 10^{-7} \, \text{m} = 406.1 \, \text{nm} $.

NEET Chemistry: Structure of Atom — Practice Set 14

Q1. The electronic configuration of an element is \( 1s^2 2s^2 2p^6 3s^2 3p^3 \). What is the atomic number of this element?

Q2. An element has 20 protons and 20 neutrons. What is its atomic mass number?

Q3. The energy required to excite an electron from \( n = 2 \) to \( n = 5 \) in a hydrogen atom is \( 4.896 \times 10^{-19} \, \text{J} \). What is the wavelength of the absorbed photon? (\( h = 6.626 \times 10^{-34} \, \text{J s} \), \( c = 3.0 \times 10^8 \, \text{m s}^{-1} \))

Q4. The ratio of the wavelengths of the first lines in the Lyman and Balmer series of a hydrogen atom is: (\( R_H = 1.097 \times 10^7 \, \text{m}^{-1} \))

Q5. The ratio of the radii of the fourth orbit of \( \text{H} \) to the third orbit of \( \text{Be}^{3+} \) is: (\( r_1 \) for H = \( 5.29 \times 10^{-11} \, \text{m} \))

Q6. An electron and an alpha particle have the same de Broglie wavelength. What is the ratio of their velocities? (\( m_e = 9.1 \times 10^{-31} \, \text{kg} \), \( m_{\alpha} = 6.64 \times 10^{-27} \, \text{kg} \))

Q7. How many possible sets of quantum numbers (\( n, l, m_l, m_s \)) are there for electrons in the \( n = 4 \) energy level?

Q8. The ratio of the kinetic energies of an electron in the second orbit of \( \text{He}^+ \) to the third orbit of \( \text{H} \) is: (\( v_1 \) for H = \( 2.19 \times 10^6 \, \text{m s}^{-1} \), \( m_e = 9.1 \times 10^{-31} \, \text{kg} \))

Q9. The de Broglie wavelength of a proton moving at \( 1.0 \times 10^6 \, \text{m s}^{-1} \) is: (\( h = 6.626 \times 10^{-34} \, \text{J s} \), \( m_p = 1.67 \times 10^{-27} \, \text{kg} \))

Q10. An ion has 17 protons and 18 electrons. What is its charge?