Photoelectron spectroscopy test answers and mark scheme for AP Chemistry (free PDF download)

The questions are on the photoelectron spectroscopy test. Take it under real conditions before reading the mark scheme.

Quick answer: Electrons fill subshells in order of energy, giving each atom a configuration. This mark scheme gives the model answers and the marks for the 8 questions of the AP Chemistry test on photoelectron spectroscopy, from configurations of manganese to radius and effective charge, with the equivalent answers to accept.

Photoelectron spectroscopy test answers and mark scheme for AP Chemistry (free PDF download)

Marks are awarded for the correct idea, the correct use of Coulomb’s law and clear units. Accept equivalent wording where the same physical reasoning appears.

Level: AP Chemistry · Curriculum: AP Chem Unit 1

Contents

Question 1 Configurations of manganese (2 marks)

[Ar] 4s² 3d⁵.
Mn²⁺ is [Ar] 3d⁵ with 5 unpaired electrons.

Marking: 1 mark each part.

Question 2 Reading a PES spectrum (3 marks)

Heights 2 : 2 : 6 : 2 mean 1s² 2s² 2p⁶ 3s², which is magnesium.
From left to right the peaks are 1s, 2s, 2p, 3s.
1s electrons are closest to the nucleus and least shielded, so they are bound most strongly.

Marking: 1 mark each part.

Question 3 Coulomb’s law (3 marks)

F ∝ Z_eff/r². The factor is 2/1.5² = 2/2.25 = 0.89.
Mg²⁺ has 12 protons and Na⁺ has 11 for the same 10 electrons, so the attraction is stronger and the ion is smaller.

Marking: 1 mark for the relation; 1 mark for the answer; 1 mark for part (b).

Question 4 Successive ionisation energies (2 marks)

There is a very large jump between the second and third values, so the third electron comes from an inner shell. The element has two valence electrons and is in group 2.

Marking: 1 mark for identifying the jump; 1 mark for the group.

Question 5 Phosphorus and sulfur (3 marks)

The valence electron lost from phosphorus comes from a singly occupied 3p orbital. In sulfur it comes from a doubly occupied 3p orbital. The two electrons in the same orbital repel each other, so removing one needs less energy. This repulsion outweighs the higher nuclear charge.

Marking: 1 mark for the orbital occupancy; 1 mark for electron repulsion; 1 mark for the conclusion.

Question 6 Order of radii (2 marks)

Mg, Na, Cl, Cl⁻ from smallest to largest. Mg has a higher nuclear charge than Na in the same shell. Cl⁻ has the largest radius because added repulsion between electrons expands the cloud.

Marking: 1 mark for the order; 1 mark for the reason.