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Electron Configurations · Paper 2 — Free Chemistry HL Practice Questions

1ChallengeSAQ-LElectron arrangement and atomic orbitals7 marksPaper 2~11 min

Data

- Speed of light:

c = 3.00 \times 10^{8}\,\text{m s}^{-1}

- Planck constant:

h = 6.63 \times 10^{-34}\,\text{J s}

- Rydberg constant:

R_H = 1.097 \times 10^{7}\,\text{m}^{-1}

A student investigates the emission spectrum of atomic hydrogen. A spectral line is observed at

486\,\text{nm}

, corresponding to the transition from

n = 4

n = 2

(Balmer series).

(a)

Calculate the energy, in J, of the photon emitted during the

n = 4

n = 2

transition. [2 marks]

(b)

Using the Rydberg equation, determine the value of

n_2

for a transition that emits a photon of wavelength

434\,\text{nm}

(another line in the Balmer series, where

n_1 = 2

). [2 marks]

(c)

State the physical significance of the integer

n_2

in the quantum mechanical model of the hydrogen atom. [1 mark]

(d)

Evaluate two limitations of the Bohr model of the hydrogen atom when applied to multi-electron atoms such as iron (Fe,

Z = 26

). In your answer, refer to atomic orbitals and the quantum mechanical model. Relevant equations:

E = h\nu \qquad c = \lambda\nu \qquad \frac{1}{\lambda} = R_H\!\left(\frac{1}{n_1^2} - \frac{1}{n_2^2}\right)

[2 marks]

Solutions

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