Molecular Orbitals
1.Which of the following diatomic species are paramagnetic and which are diamagnetic?
a.C2^2+
b.B2^2-
c.Li2^-
2.Arrange the following in order of decreasing stability.
a.F2
b.F2^-
c.F2+
I know that as you go to higher subshells like from s -p-d-f the energy increases.
1. To determine whether a diatomic species is paramagnetic or diamagnetic, we need to look at the molecular orbital (MO) diagram and the number of unpaired electrons.
a. C2^2+: C2^2+ has a total of 12 valence electrons. The MO diagram for C2^2+ consists of bond orbitals and antibonding orbitals. Both electrons in the σ1s orbital are paired, resulting in diamagnetic behavior.
b. B2^2-: B2^2- has a total of 14 valence electrons. The MO diagram for B2^2- also contains bond orbitals and antibonding orbitals. The two extra electrons in the antibonding π2p* orbitals are unpaired, resulting in paramagnetic behavior.
c. Li2^-: Li2^- has a total of 8 valence electrons. The MO diagram for Li2^- also consists of bond orbitals and antibonding orbitals. Both electrons are paired in the σ1s orbital, resulting in diamagnetic behavior.
2. To determine the stability order, we need to consider the number of electrons and their configurations.
a. F2: F2 has a total of 18 valence electrons. According to the Aufbau principle, the electrons fill the molecular orbitals starting from the lowest energy level. The molecular orbital diagram for F2 shows that all the electrons are paired, resulting in diamagnetic behavior. However, it does not have any extra stabilization or destabilization due to additional electrons.
b. F2^-: F2^- has a total of 19 valence electrons. One extra electron is added to the antibonding π*2p orbital, making it paramagnetic. The additional electron and its location in the antibonding orbital contribute to destabilization, making it less stable than F2.
c. F2+: F2+ has a total of 17 valence electrons. One electron is removed from the antibonding π2p orbital, resulting in the stabilization of the molecule. Therefore, F2+ is more stable than both F2 and F2^-.
Therefore, the order of decreasing stability is:
F2+ > F2 > F2^-
To determine whether a diatomic species is paramagnetic or diamagnetic, you need to understand molecular orbital theory. In molecular orbital theory, molecular orbitals are formed by combining atomic orbitals from the individual atoms in the molecule.
1. Paramagnetic vs. Diamagnetic:
Paramagnetic species have unpaired electrons in their molecular orbitals, making them attracted to a magnetic field. Diamagnetic species, on the other hand, have all electrons paired, resulting in no attraction to a magnetic field.
To determine whether a diatomic species is paramagnetic or diamagnetic, you can follow these steps:
a. Write the electron configuration of each diatomic species.
b. Determine the total number of electrons in the molecular orbitals by counting the electrons in the molecular orbitals obtained from the electron configuration.
c. Check whether any electrons are unpaired. If there are unpaired electrons, the species is paramagnetic. If all electrons are paired, the species is diamagnetic.
Let's analyze the species you provided:
a. C2^2+:
The electron configuration of carbon is 1s^2 2s^2 2p^2, and for C2^2+, two electrons are removed. Therefore, the molecular orbital diagram for C2^2+ is σ1s^2 σ*1s^2 σ2s^2 σ*2s^2 π2px^2 π2py^2 π*2px^1 π*2py^1. There are two unpaired electrons in the π*2px and π*2py orbitals, making C2^2+ paramagnetic.
b. B2^2-:
The electron configuration of boron is 1s^2 2s^2 2p^1, and for B2^2-, an extra electron is added. Therefore, the molecular orbital diagram for B2^2- is σ1s^2 σ*1s^2 σ2s^2 σ*2s^2 π2px^2 π2py^2 π*2px^2 π*2py^2. All the electrons are paired, resulting in B2^2- being diamagnetic.
c. Li2^-:
The electron configuration of lithium is 1s^2 2s^1, and for Li2^-, an extra electron is added. Therefore, the molecular orbital diagram for Li2^- is σ1s^2 σ*1s^2 σ2s^2 σ*2s^2 π2px^2 π2py^2 π*2px^2 π*2py^2. All the electrons are paired, making Li2^- diamagnetic.
2. Stability:
To determine the relative stability of the given diatomic species, you need to consider the bond order. Bond order is calculated by subtracting the number of antibonding electrons from the number of bonding electrons and dividing the result by 2.
The general rule is that higher bond order implies greater stability.
a. F2:
The electron configuration of fluorine is 1s^2 2s^2 2p^5. Therefore, the molecular orbital diagram for F2 is σ1s^2 σ*1s^2 σ2s^2 σ*2s^2 π2px^2 π2py^2 π2p(z)^4. In this case, there are 10 bonding electrons and 4 antibonding electrons, resulting in a bond order of (10 - 4)/2 = 3. F2 has the highest bond order among the given species, making it the most stable.
b. F2^-:
The molecular orbital diagram for F2^- is the same as F2, except that one electron is added to the π2p(z) orbital. Thus, there are 11 bonding electrons and 4 antibonding electrons, resulting in a bond order of (11 - 4)/2 = 3.5. F2^- has a slightly higher bond order than F2, making it more stable.
c. F2+:
The molecular orbital diagram for F2+ is the same as F2, except that one electron is removed from the π2p(z) orbital. Therefore, there are 9 bonding electrons and 4 antibonding electrons, resulting in a bond order of (9 - 4)/2 = 2.5. F2+ has the lowest bond order among the three species, making it the least stable.
In summary, the decreasing order of stability is b. F2^- > a. F2 > c. F2+.
I answered this for someone last night. What you want to do is to look for unpaired electrons. That leads to paramagnetism. Elements in which all electrons are paired are diamagnetic.
Here is how you do the first one, C^+2.
First, let's do the electron configuration of the element.
6C = 1s2 2s2 2p2
When we make the +2 ion, we remove the outer two electrons so the +2 ion has an electron configuration of
1s2 2s2
Remembering that the s orbital may hold only two electrons, we know that the electrons in this arrangement must be paired; therefore, C^+2 is diamagnetic. The others are done the same way.
Regarding the F problem, you know F2 is very reactive; however, it is stable as a molecule.