Multiple Choice
How many electron-containing orbitals are present in a neutral atom of arsenic (atomic number 33)?
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10. Periodic Properties of the Elements
The Electron Configuration
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A ground state atom of Mg could not have any electrons with which of the following electron configurations?
A
n = 1, l = 0, m_l = 0, m_s = +1/2
B
n = 3, l = 2, m_l = 0, m_s = +1/2
C
n = 2, l = 1, m_l = -1, m_s = -1/2
D
n = 3, l = 0, m_l = 0, m_s = -1/2
Verified step by step guidance1
Step 1: Understand the quantum numbers and their meaning. The four quantum numbers are: principal quantum number \(n\), azimuthal (angular momentum) quantum number \(l\), magnetic quantum number \(m_l\), and spin quantum number \(m_s\). Each electron in an atom is described by a unique set of these numbers.
Step 2: Recall the electron configuration of a ground state magnesium (Mg) atom. Magnesium has 12 electrons, and its ground state electron configuration is \$1s^2 2s^2 2p^6 3s^2\(. This means electrons fill up to \)n=3\(, \)l=0$ (the 3s orbital) in the ground state.
Step 3: Analyze the given quantum numbers for each electron configuration option to determine if they correspond to an allowed electron in the ground state of Mg. Check if the quantum numbers correspond to orbitals that are occupied in the ground state or if they violate any quantum rules.
Step 4: Specifically, check the option \(n=3\), \(l=2\), \(m_l=0\), \(m_s=+1/2\). Here, \(l=2\) corresponds to a d orbital. Since Mg's ground state electron configuration does not include any electrons in the 3d orbitals (which would be \(n=3\), \(l=2\)), this configuration cannot be present in the ground state.
Step 5: Confirm that the other options correspond to orbitals that are occupied in the ground state or are allowed by the quantum numbers for Mg's electrons. Thus, the configuration with \(n=3\), \(l=2\), \(m_l=0\), \(m_s=+1/2\) is the one that cannot exist for a ground state Mg atom.
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