Chemistry Test Atomic Structure 2 — Questions and Answers
Question 1: Which quantum number describes the shape of an atomic orbital?
- Principal quantum number (n)
- Angular momentum quantum number (l) (Correct answer)
- Magnetic quantum number (ml)
- Spin quantum number (ms)
Correct answer: Angular momentum quantum number (l)
The angular momentum quantum number (l) defines the shape of the orbital, with values 0, 1, 2, 3 corresponding to s, p, d, f orbitals.
Question 2: An atom has 17 protons and 18 neutrons. What is its mass number?
- 17
- 18
- 35 (Correct answer)
- 1
Correct answer: 35
Mass number equals protons plus neutrons, so 17 + 18 = 35.
Question 3: Which of the following correctly describes isotopes?
- Atoms with the same mass number but different atomic numbers
- Atoms with the same number of protons but different numbers of neutrons (Correct answer)
- Atoms with the same number of electrons but different numbers of protons
- Atoms with the same number of neutrons but different numbers of electrons
Correct answer: Atoms with the same number of protons but different numbers of neutrons
Isotopes are atoms of the same element (same proton count) that differ in the number of neutrons.
Question 4: In Bohr's model of the hydrogen atom, what happens when an electron absorbs energy?
- It moves to a lower energy level
- It is ejected from the atom
- It jumps to a higher energy level (Correct answer)
- It slows down in its orbit
Correct answer: It jumps to a higher energy level
When an electron absorbs a photon of sufficient energy, it transitions to a higher (farther from nucleus) energy level.
Question 5: What is the maximum number of electrons that can occupy the third principal energy level (n=3)?
- 8
- 10
- 18 (Correct answer)
- 32
Correct answer: 18
The maximum electrons per shell is given by 2n², and for n=3: 2(3)² = 18.
Question 6: Which subshell is filled after the 4s subshell according to the Aufbau principle?
- 4p
- 3d (Correct answer)
- 4d
- 5s
Correct answer: 3d
According to the Aufbau principle and the n+l rule, the 3d subshell (n+l=5) fills after 4s (n+l=4).
Question 7: A neutral atom has an electron configuration of 1s²2s²2p⁶3s²3p⁵. How many valence electrons does it have?
- 5
- 7 (Correct answer)
- 2
- 17
Correct answer: 7
Valence electrons are in the outermost shell; the 3s²3p⁵ configuration gives 2+5 = 7 valence electrons.
Chemistry Test Atomic Structure 2
Which quantum number describes the shape of an atomic orbital?