Structure of Atom (Advanced)

CBSE Science. Optional Advanced level: cathode and canal rays, the neutron, line spectra, hydrogen series and the Rydberg equation, Rutherford and Bohr models. Every sheet has 20 questions in three sections and an answer key, and the numbers change every time.

Open a printable sample sheet Cheat sheet: formulas and key points

Sample questions

Real questions from this chapter, as the app sets them. Tap Answer to see the answer and working.

Section A · multiple choice

1.
In a hydrogen atom, an electron jumps from level n = 4 down to n = 1. The line given out belongs to the:
1. Lyman series
2. Balmer series
3. Pfund series
4. Paschen series
Answer
(a) Lyman series
a series is named by the lower level the electron falls to: n = 1 is Lyman
2.
Using the Rydberg equation (R = 109,677 cm⁻¹), the wave number of the hydrogen line for a jump from n = 3 to n = 2 is about:
1. 39,606 cm⁻¹
2. 18,280 cm⁻¹
3. 12,186 cm⁻¹
4. 15,233 cm⁻¹
Answer
(d) 15,233 cm⁻¹
R(1/2² − 1/3²) = 109,677 × 5/36
3.
Electrons in a sample of hydrogen atoms are excited to level n = 9. As they fall back, by every possible jump, as far as n = 1, how many different spectral lines can appear?
1. 45
2. 8
3. 36
4. 81
Answer
(c) 36
levels 1 to 9 are 9 levels; any two give a line: 9 × 8 ÷ 2

Section B · short answer

4.
Using R = 109,677 cm⁻¹, find the wave number of the hydrogen line for a jump from n = 7 to n = 3. Give the answer to the nearest whole number, in cm⁻¹ (per cm).
Answer
9,948 per cm
R(1/3² − 1/7²) = 109,677 × 40/441 = 9,948.03
5.
An electron in a hydrogen atom falls from n = 5 to n = 4. Name the series of the line given out.
Answer
Brackett
the lower level, n = 4, names the series

Section C · long answer

6.
Helium has two protons, yet its mass is about four times that of hydrogen. What did this suggest, and how was it settled?
Answer
It suggested a neutral particle in the nucleus that adds mass. Chadwick found it in 1932: the neutron, with about the mass of a proton. Helium has 2 protons and 2 neutrons.
marking: each point in the model answer

Fresh sheets for your child

In the app, every Structure of Atom (Advanced) sheet is new: the app remembers the questions your child has already had and leaves them out. Print the sheet as a PDF, or use notebook mode and write the answers in a notebook.

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