ECAT Chemistry — Atomic Structure
Atomic Structure is part of the Chemistry section of the UET ECAT (30 of the 100 MCQs). It breaks into 4 subtopics, and we hold 40 ECAT-pattern practice MCQs on it, each with a written explanation. Tap a subtopic below to practise just that.
Subtopics (4)
How Atomic Structure is tested
Across the 7 ECAT past papers on ParhaiKrlo, Atomic Structure accounts for 13 questions. It appears in all 7, about 1.9 questions a paper. The heaviest was ECAT Past Paper 04, with 3 questions, and the most recent is ECAT Past Paper 07, with 1.
| Paper | Questions |
|---|---|
| ECAT Past Paper 07 | 1 |
| ECAT Past Paper 06 | 2 |
| ECAT Past Paper 05 | 1 |
| ECAT Past Paper 04 | 3 |
| ECAT Past Paper 03 | 2 |
| ECAT Past Paper 02 | 3 |
| ECAT Past Paper 01 | 1 |
Atomic Structure MCQs from the ECAT past papers
Try each one before opening the answer. Each comes with a short explanation.
- Q1 · ECAT Past Paper 07 · Atomic Structure
Photons emitted when electrons in a hydrogen atom fall from higher levels to the n = 1 level lie in the:
- A.Visible region
- B.Infrared region
- C.X-ray region
- D.Ultraviolet region
Show answer
Answer: D. Ultraviolet region — Transitions to n = 1 form the Lyman series, in the ultraviolet.
- Q2 · ECAT Past Paper 06 · Atomic Structure
Which electronic configuration of nitrogen is correct according to Hund's rule?
- A.1s² 2s² 2pₓ¹ 2p_y¹ 2p_z¹
- B.1s² 2s² 2pₓ² 2p_y¹
- C.1s² 2s¹ 2pₓ² 2p_y¹ 2p_z¹
- D.1s² 2s² 2pₓ³
Show answer
Answer: A. 1s² 2s² 2pₓ¹ 2p_y¹ 2p_z¹ — Hund's rule: the three 2p electrons occupy the three 2p orbitals singly, with parallel spins.
- Q3 · ECAT Past Paper 05 · Atomic Structure
Which statement about cathode rays is NOT correct?
- A.They can ionize a gas
- B.They possess momentum
- C.They cannot cause chemical changes
- D.They are deflected by a magnetic field
Show answer
Answer: C. They cannot cause chemical changes — Cathode rays (fast electrons) ionize gases, carry momentum, are deflected by fields and DO cause chemical changes (e.g. on photographic plates).