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#ionization energy

28 public questions tagged with this topic.

In Bohr’s model, what happens to the energy required to ionize a hydrogen atom as the electron’s orbit number increases?

**Bohr energy levels** E_n = -13.6/n² eV for hydrogen, negative indicating bound state, total energy = -13.6 eV ground state n=1, -3.4 eV n=2, -1.51 eV n=3, etc., photon energy for transition n_i → n_f is ΔE =13.6(1/n_f² -1/n_i²) eV, wavelength λ = hc/ΔE, h=6.6×10⁻³⁴ J·s, c=3×10⁸ m/s. Emission line spectrum characterized by discrete wavelengths because energy levels discrete. As n increases, the energy becomes less negative (closer to zero), so less energy is required to ionize the atom from higher orbits. Using E_n = -13.6/n² eV, r_n = n² a₀, L = n h/2π, R = R₀ A^¹/³, BE = Δm c² and 1

Ref: NCERT > Physics Book > Atoms and Nuclei > Bohr Model Energy Levels and Hydrogen Spectrum

What is the energy required to ionize a hydrogen atom from its ground state? (Ground state energy = -13.6 eV)

**Hydrogen transitions** example n=3→n=1 ΔE=13.6(1-1/9)=12.09 eV, photon 12.09 eV, λ=1240/12.09≈102.6 nm Lyman series, n=3→n=2 ΔE=1.89 eV Balmer visible Hα 656 nm. Absorption photon energy must match difference, if atom in n=2 absorbs 1.89 eV jumps to n=3, if absorbs 12.75 eV from ground 1→4 because -13.6+12.75=-0.85 eV = -13.6/16. Ionization energy = energy to reach E = 0 from ground state. E₁ = -13.6 eV , E_∞ = 0 eV . Energy required = 0 - (-13.6) = 13.6 eV . Using E_n = -13.6/n² eV, r_n = n² a₀, L = n h/2π, R = R₀ A^¹/³, BE = Δm c² and 1 u

Ref: NCERT > Physics Book > Atoms and Nuclei > Bohr Model Energy Levels and Hydrogen Spectrum

The ionization energy of donor electrons in an n-type semiconductor is:

**Doping** is adding impurity to pure semiconductor to increase carriers, pentavalent (P, As, Sb) donates extra electron, 1 ppm doping in Ge with 4×10²⁸ atoms/m³ gives donor density N_d = 4×10²⁸×10⁻⁶ =4×10²² m⁻³ for 1 ppm, acceptor atoms p-type trivalent B, Al, Ga. Overall charge neutrality maintained because donor ion core positive but electron negative, net neutral. The fifth electron of a pentavalent dopant (e.g., As) in Si or Ge is weakly bound, requiring very small energy (~0.01 eV for Ge, ~0.05 eV for Si) to become free, much less than the intrinsic energy gap. Substituting values gives

Ref: NCERT > Physics Book > Electronic Devices > Doping, Charge Carriers and Conductivity

Which element in the fourth period has the highest third ionization enthalpy?

Third ionization enthalpy peaks when removing an electron from a noble gas-like X²⁺ ion. Ca (after losing two electrons, becomes Ca²⁺ with 1s² 2s² 2p⁶ 3s² 3p⁶) has the highest value.

Ref: NCERT Class 11 Chemistry > Chapter 3: Classification of Elements and Periodicity in Properties > Topic: Periodic Trends - Atomic Radii Ionic Radii and Ionization Enthalpy

Which element in the fourth period has the highest fourth ionization enthalpy?

Fourth ionization enthalpy peaks when removing an electron from a stable X³⁺ ion. Si (after losing three electrons, becomes Si³⁺ with 1s² 2s² 2p⁶) has the highest value.

Ref: NCERT Class 11 Chemistry > Chapter 3: Classification of Elements and Periodicity in Properties > Topic: Periodic Trends - Atomic Radii Ionic Radii and Ionization Enthalpy

Which element in the fifth period has the highest third ionization enthalpy?

Third ionization enthalpy peaks when removing an electron from a noble gas-like X²⁺ ion. Sr (after losing two electrons, becomes Sr²⁺ with 1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶) has the highest value in period 5.

Ref: NCERT Class 11 Chemistry > Chapter 3: Classification of Elements and Periodicity in Properties > Topic: Periodic Trends - Atomic Radii Ionic Radii and Ionization Enthalpy

Which of the following has the highest first ionization enthalpy among the third period elements?

First ionization enthalpy increases across a period. Among Na, Mg, Si, and Ar, Ar (group 18, period 3) has the highest value due to its stable noble gas configuration.

Ref: NCERT Class 11 Chemistry > Chapter 3: Classification of Elements and Periodicity in Properties > Topic: Periodic Trends - Atomic Radii Ionic Radii and Ionization Enthalpy

Which element in group 14 has the highest ionization enthalpy after losing three electrons?

Fourth ionization enthalpy is highest for C (removing an electron from C³⁺ with 1s²) due to its small size and stable configuration, compared to Si, Ge, or Sn.

Ref: NCERT Class 11 Chemistry > Chapter 3: Classification of Elements and Periodicity in Properties > Topic: Periodic Trends - Atomic Radii Ionic Radii and Ionization Enthalpy

Which element in the fourth period has the highest fifth ionization enthalpy?

Fifth ionization enthalpy peaks when removing an electron from a stable X⁴⁺ ion. P (after losing four electrons, becomes P⁴⁺ with 1s² 2s² 2p⁶) has the highest value in period 4.

Ref: NCERT Class 11 Chemistry > Chapter 3: Classification of Elements and Periodicity in Properties > Topic: Periodic Trends - Atomic Radii Ionic Radii and Ionization Enthalpy

Which element has the highest third ionization enthalpy among the following?

Third ionization enthalpy is highest when removing an electron from a noble gas-like configuration. Mg (after losing two electrons, becomes Mg²⁺ with 1s² 2s² 2p⁶) has the highest value.

Ref: NCERT Class 11 Chemistry > Chapter 3: Classification of Elements and Periodicity in Properties > Topic: Periodic Trends - Atomic Radii Ionic Radii and Ionization Enthalpy