The mass of a proton is approximately equal to the mass of a

Answer: Neutron Protons and neutrons each have mass ≈ 1 amu; electrons are 1/1836 the mass of a proton.

The electron configuration of a neutral oxygen atom is

Answer: 1s² 2s² 2p⁴ Oxygen has 8 electrons: 2 in 1s, 2 in 2s, 4 in 2p. Configuration 1s² 2s² 2p⁴.

The shape of an s orbital is

Answer: Spherical s orbitals are spherical (l = 0). p orbitals are dumbbell-shaped (l = 1). d orbitals are mostly cloverleaf (l = 2).

AP Chemistry · Topic 1.5

Atomic Structure and Electron Configuration Practice

Part of Atomic Structure and Properties.(SAP-1.A)

Practice questions

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Sample questions

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Sample 1difficulty 1/5
$The mass of a proton is approximately equal to the mass of a$
- A
  $Helium atom$
- B
  $Hydrogen atom$
- C
  $Neutron$
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- D
  $Electron$
Why
$Protons and neutrons each have mass \approx 1 amu; electrons are ~1/1836 the mass of a proton.$
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Sample 2difficulty 2/5
$The electron configuration of a neutral oxygen atom is$
- A
  $1s² 2s² 2p⁴$
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- B
  $1s² 2s² 2p⁶$
- C
  $1s¹ 2s² 2p⁵$
- D
  $1s² 2s² 2p²$
Why
$Oxygen has 8 electrons: 2 in 1s, 2 in 2s, 4 in 2p. Configuration 1s² 2s² 2p⁴.$
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Sample 3difficulty 2/5
$The shape of an s orbital is$
- A
  $Square$
- B
  $Dumbbell$
- C
  $Spherical$
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- D
  $Cloverleaf$
Why
$s orbitals are spherical (l = 0). p orbitals are dumbbell-shaped (l = 1). d orbitals are mostly cloverleaf (l = 2).$
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Sample 4difficulty 2/5
$A 2p subshell can hold at most how many electrons?$
- A
  $10$
- B
  $8$
- C
  $6$
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- D
  $2$
Why
$A p subshell has 3 orbitals (m_l = -1, 0, +1), each holding 2 electrons \to 6 total.$
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Sample 5difficulty 2/5
$The Aufbau ("building up") principle says that electrons fill$
- A
  $The highest-energy orbital first$
- B
  $Only outer shells$
- C
  $All orbitals simultaneously$
- D
  $Lower-energy orbitals first, then higher$
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Why
$Build from low to high energy: 1s \to 2s \to 2p \to 3s \to 3p \to 4s \to 3d \to 4p \to ...$
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