Four quantum numbers that could represent the last electron added (using the Aufbau principle) to the Argon atom. A n = 2, l =0, m_l = 1, m_s = +\frac12 B n = 3, l =0, m_l = 1, m_s = -\frac12 C n = 3, l =1, m_l = 1, m_s = +\frac12 D n = 3, l =2, m_l = 1, m_s = -\frac12

Explanation:

Argon atom has atomic number 18. Then, it has 18 protons and 18 electrons.

To determine the quantum numbers you must do the electron configuration.

Aufbau's principle is a mnemonic rule to remember the rank of the orbitals in increasing order of energy.

The rank of energy is:

1s < 2s < 2p < 3s < 3p < 4s < 3d < 4p < 5s < 4d < 5p < 6s < 4f < 5d < 6p < 7s < 5f < 6d < 7d

You must fill the orbitals in order until you have 18 electrons:

The last electron is in the 3p orbital.

The quantum numbers associated with the 3p orbitals are:

Thus, the six possibilities for the last six electrons are:

Hence, the correct choice is:

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