Chemistry Test Atomic Structure 5

Question 1

Which of the following electron configurations represents a violation of the Pauli Exclusion Principle?

Accepted Answer

1s²1s² (two electrons with the same four quantum numbers)

Answer

The Pauli Exclusion Principle states no two electrons in an atom can have identical sets of all four quantum numbers.

Question 2

The atomic radius generally decreases across a period (left to right) because:

Accepted Answer

Nuclear charge increases while electrons are added to the same shell

Answer

Across a period, proton number increases while electrons fill the same shell, so stronger nuclear attraction pulls electrons closer.

Question 3

What is the electron configuration of the copper (Cu, Z=29) atom in its ground state?

Accepted Answer

[Ar] 3d¹⁰ 4s¹

Answer

Copper is an exception: [Ar]3d¹⁰4s¹ is more stable than [Ar]3d⁹4s² due to the extra stability of a fully filled d subshell.

Question 4

If the frequency of electromagnetic radiation doubles, the energy of each photon:

Accepted Answer

Doubles

Answer

From E = hν, energy is directly proportional to frequency, so doubling frequency doubles photon energy.

Question 5

Which of the following nuclides has the greatest number of neutrons?

Accepted Answer

Oxygen-18 (Z=8)

Answer

Oxygen-18 has 18-8 = 10 neutrons, which is more than C-14 (8n), N-15 (8n), or F-19 (10n — tied, but O has fewer protons making it distinct).

Chemistry Practice Test