What is the l quantum number for the last electron added in the Aufbau procedure for forming the electron configuration of barium?
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To determine the l quantum number for the last electron added in the Aufbau procedure for forming the electron configuration of barium, we need to first know the electron configuration of barium.
Barium (Ba) has an atomic number of 56, which means it has 56 electrons. The Aufbau principle states that electrons occupy the lowest-energy orbitals available, following a specific order. The order is as follows: 1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s, 4d, 5p, 6s, 4f, 5d, 6p, 7s, etc.
To find the electron configuration of barium, we need to start filling the orbitals in this specific order. We fill the orbitals one by one, from lowest to highest energy, until we reach barium's atomic number of 56.
Starting with the 1s orbital, we fill it with two electrons (1s²). Then, we move to the 2s orbital and add two more electrons (2s²). Next, we move to the 2p orbital and fill it with six electrons (2p⁶). Now we have 2+2+6=10 electrons accounted for.
Moving on, we fill the 3s orbital with two electrons (3s²). Then, we fill the 3p orbital with six more electrons (3p⁶). So far, we have 10+2+6=18 electrons.
Continuing, we fill the 4s orbital with two electrons (4s²) and then move to the 3d orbital. The 3d orbital can hold up to 10 electrons, and we fill it completely, adding 10 more electrons (3d¹⁰). Now, we have 18+2+10=30 electrons.
Next, we fill the 4p orbital with six electrons (4p⁶), bringing the total to 30+6=36 electrons accounted for.
At this point, we have reached the 5s orbital. The 5s orbital can hold up to two electrons, and we place two electrons in it (5s²). Now, the total number of electrons is 36+2=38.
Finally, we move to the 4d orbital, which can hold up to 10 electrons. We fill the 4d orbital with 10 more electrons (4d¹⁰), making the total number of electrons 38+10=48.
Since the Aufbau procedure follows the order 1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s, 4d, 5p, 6s, 4f, 5d, 6p, 7s, etc., we can conclude that the last electron added for barium is in the 6s orbital.
Therefore, the l quantum number for the last electron added in the Aufbau procedure for forming the electron configuration of barium is 0.