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AP Chemistry Unit 1: Atomic Structure and Properties

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Unit 1: Atomic Structure and Properties

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Question 1

Which of the following correctly ranks the species by increasing atomic/ionic radius?

$C l^{-}, Cl, N a^{+}, Na$

N a^{+} < C l^{-} < Na < Cl

N a^{+} < Na < C l^{-} < Cl

N a^{+} < Cl < Na < C l^{-}

Cl < N a^{+} < Na < C l^{-}

Question 2

Which electron configuration correctly represents a ground-state sulfur ( $Z = 16$ ) atom?

[Ne] 3 s^{2} 3 p^{4}

[Ne] 3 s^{2} 3 p^{6}

[Ne] 3 s^{2} 3 p^{2}

[Ne] 3 s^{1} 3 p^{5}

Question 3

Which of the following correctly orders the elements by increasing first ionization energy?

$Li, Na, K$

Li < Na < K

K < Na < Li

Na < K < Li

Li < K < Na

Question 4

Spectral lines in the visible emission spectrum of hydrogen are produced when an electron transitions from a higher energy level to:

Select the statement that is both correct and explains the underlying mechanism.

n = 1

, releasing ultraviolet photons equal in energy to the transition.B.

n = 2

, releasing a photon whose energy equals the difference in quantized energy levels.C.

n = 3

, releasing infrared radiation.D.

n = 2

, absorbing a photon to move to a lower energy state.

Question 5

Atomic radii generally decrease across a period (left to right). What is the primary reason for this trend?

A.Electrons are added to successively lower energy levels.B.The principal quantum number

n

decreases across a period.C.Increasing nuclear charge pulls the electron cloud closer while the shielding from added electrons in the same shell is minimal.D.Increased electron–electron repulsion compresses the electron cloud.

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Question 6

A PES spectrum shows two peaks for an element: a very high binding-energy peak with relative area 1, and a low binding-energy peak with relative area 2. Which element is this?

A.HeliumB.LithiumC.BerylliumD.Boron

Question 7

According to Coulomb's law, the energy of attraction between an electron and the nucleus is proportional to $\frac{Z _{eff}}{r}$ . Which isoelectronic pair would have the electron held most tightly (most negative energy)?

O^{2 -}

F^{-}

Ne

M g^{2 +}

Question 8

A photoelectron spectrum of an unknown element shows peaks at binding energies of approximately 2470, 190, 99, and 11 eV. Based on the pattern of peaks and the known PES of the elements, which element is this most likely to be?

A.CarbonB.NeonC.MagnesiumD.Silicon

Question 9

An element's fifth ionization energy is dramatically larger than its fourth. What does this indicate about the element's electron configuration?

A.The element is in Group 4 of the periodic table.B.The element is in Group 5 of the periodic table.C.The element has five valence electrons.D.The fourth and fifth electrons occupy the same orbital.

Question 10

In a mass spectrometry experiment, a sample of neon gas produces peaks at $m / z = 20, 21,$ and $22$ . What do the different $m / z$ values represent?

A.Different ions of neon with varying chargesB.Neon atoms that lost different numbers of electronsC.Isotopes of neon with different numbers of neutronsD.Impurities in the neon sample

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Question 11

An element has two naturally occurring isotopes: one with mass 10.013 u (19.9% abundance) and one with mass 11.009 u (80.1% abundance). What is the weighted average atomic mass?

10.51 u

10.81 u

11.01 u

10.21 u

Question 12

The Bohr model correctly predicts the emission spectrum of hydrogen. However, it fails for multi-electron atoms primarily because it:

A.Assumes circular orbits and ignores electron–electron repulsion.B.Does not quantize electron energy levels.C.Ignores the wave nature of light entirely.D.Places electrons in the nucleus.

AP Chemistry Unit 1: Atomic Structure and Properties — Free with Answer Explanations | Test Practice Hub