Which of the following is a possible set of n, l, ml, and ms quantum numbers for the last electron added to form an As3+ ion?


(a)

3, 1, -1, ½

(b)

4, 0, 0, -½

(c)

3, 2, 0, ½

(d)

4, 1, -1, ½

(e)

5, 0, 0, ½

As is [Ar]3d10 4s2 4p3. To make the +3 ion we remove the last three electrons so the last electron added is the 4s.

n = 4
all s electrons are l = 0
the spin of an s electron is either +1/2 or -1/2. You should be able to pick out the answer from this.

If the energy state of the H-atom is changed from n=3 to n=2:

What is the energy change in joules?

Energy Change = J

What is the frequency of the photon emitted?
Frequency = Hz

To determine the possible set of quantum numbers for the last electron added to form an As3+ ion, we need to understand the rules governing the assignment of quantum numbers.

The principal quantum number (n) represents the energy level or shell of the electron. The azimuthal quantum number (l) represents its orbital shape, and it can range from 0 to n-1. The magnetic quantum number (ml) represents the orientation of the orbital in 3D space, and it can range from -l to +l. The spin quantum number (ms) represents the spin of the electron and can have values of +½ or -½.

For an As3+ ion, the atomic number of arsenic (As) is 33, which means it has 33 electrons. The 3+ charge indicates that it has lost 3 electrons, leaving 30 remaining.

We need to find the electron that was last added to the ion. To do this, we can use the Aufbau principle, which states that electrons fill orbitals in increasing order of energy.

Starting with the lowest energy levels, we have the following electron configuration for As: 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p³.

To get the electron configuration for As3+, we remove three electrons from the highest energy levels: 1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰.

Now, we look at the remaining electron configuration to determine the last electron added. In this case, it is taken from the 3p orbital.

Looking at the answer choices:

(a) 3, 1, -1, ½: This implies the electron is in the 3p orbital with l = 1 and ml = -1, and has a positive spin (+½). However, for As3+, the spin would be negative (-½) due to the removal of electrons.

(b) 4, 0, 0, -½: This implies the electron is in the 4s orbital, which contradicts the electron configuration we determined.

(c) 3, 2, 0, ½: This implies the electron is in the 3d orbital, which contradicts the electron configuration we determined.

(d) 4, 1, -1, ½: This implies the electron is in the 4p orbital with l = 1 and ml = -1, and has a positive spin (+½). This matches the electron configuration determined earlier, so it is a possible set of quantum numbers for the last electron added.

(e) 5, 0, 0, ½: This implies the electron is in the 5s orbital, which contradicts the electron configuration we determined.

Therefore, the correct answer is (d) 4, 1, -1, ½.