Electrical conductivity of alkali metals
Hi
Why does the electrical conductivity of alkali metals generally decrease down the group when outermost electrons get further from the nucleus?
Why does the electrical conductivity of alkali metals generally decrease down the group when outermost electrons get further from the nucleus?
Reply 1
A simple explanation I have come across is the lower electron density down the group, which makes the metals less conductive. However, it seems that the trend is an increase from Li --> Na, but then a decrease in conductivity from Na --> Cs, which at first raises doubts about that explanation.
https://periodictable.com/Properties/A/ElectricalConductivity.an.html
Interestingly, the trend in electrical conductivities down the group seems to mirror the trend in standard reduction potentials of the monovalent group 1 cations down the group (e.g Li has a more -ve standard reduction potential than Na, but from Na to Cs, the standard reduction potentials get more negative). The standard reduction potentials are explained rather trivially because Li+ has a higher hydration energy than the rest of the group 1 metal cations due to its charge density. My best guess in light of this apparent similarity in trends would be that perhaps Li is less conductive than Na because the metal cations are so charge-dense they bind the electrons more tightly, which makes them less able to carry a current and then from Na --> Cs, the electron-density decreases so sharply that the current is less easily carried by the delocalised electron cloud.
https://periodictable.com/Properties/A/ElectricalConductivity.an.html
Interestingly, the trend in electrical conductivities down the group seems to mirror the trend in standard reduction potentials of the monovalent group 1 cations down the group (e.g Li has a more -ve standard reduction potential than Na, but from Na to Cs, the standard reduction potentials get more negative). The standard reduction potentials are explained rather trivially because Li+ has a higher hydration energy than the rest of the group 1 metal cations due to its charge density. My best guess in light of this apparent similarity in trends would be that perhaps Li is less conductive than Na because the metal cations are so charge-dense they bind the electrons more tightly, which makes them less able to carry a current and then from Na --> Cs, the electron-density decreases so sharply that the current is less easily carried by the delocalised electron cloud.
Reply 2
Original post
by Joshua VIctorHi
Why does the electrical conductivity of alkali metals generally decrease down the group when outermost electrons get further from the nucleus?
Why does the electrical conductivity of alkali metals generally decrease down the group when outermost electrons get further from the nucleus?
Hello Joshua VIctor!
Here is another possible explanation.
The electrical conductivity of alkali metals decreases throughout the group when the electrons move away from the nucleus, as they lose their mobility and are less involved in the transport of electrical charge.
Electrons with higher energy can be transferred easily from atom to atom when closer to the nucleus, enabling a greater electrical conductivity. At the same time, as the electrons move away from the nucleus, their freedom of movement decreases, resulting in a decrease in the electric conductivity of the element.
Bye,
Reply 3
Original post
by NitrotolueneHello Joshua VIctor!
Here is another possible explanation.
The electrical conductivity of alkali metals decreases throughout the group when the electrons move away from the nucleus, as they lose their mobility and are less involved in the transport of electrical charge.
Electrons with higher energy can be transferred easily from atom to atom when closer to the nucleus, enabling a greater electrical conductivity. At the same time, as the electrons move away from the nucleus, their freedom of movement decreases, resulting in a decrease in the electric conductivity of the element.
Bye,
Sandro
Here is another possible explanation.
The electrical conductivity of alkali metals decreases throughout the group when the electrons move away from the nucleus, as they lose their mobility and are less involved in the transport of electrical charge.
Electrons with higher energy can be transferred easily from atom to atom when closer to the nucleus, enabling a greater electrical conductivity. At the same time, as the electrons move away from the nucleus, their freedom of movement decreases, resulting in a decrease in the electric conductivity of the element.
Bye,
I’d be very surprised if the outer electrons were becoming less mobile down the group - usually the further out the outer electrons are, the more shielding they experience and the less effect the nucleus has on them. The result is less tightly bound electrons that should be more mobile.
I would think it’s more likely to be a combination of how mobile the electrons are and how many charge carriers there are per unit space. Li has the most charge carriers per unit space, but the least mobile electrons because they are more tightly bound and even though Cs has the least tightly bound outer electron, the fact Cs is just so much larger than the other group 1 metals means it has far fewer charge carriers per unit space. This may explain in large part why Na has the highest electrical conductivity in the group.
Reply 4
Original post
by NitrotolueneHello Joshua VIctor!
Here is another possible explanation.
The electrical conductivity of alkali metals decreases throughout the group when the electrons move away from the nucleus, as they lose their mobility and are less involved in the transport of electrical charge.
Electrons with higher energy can be transferred easily from atom to atom when closer to the nucleus, enabling a greater electrical conductivity. At the same time, as the electrons move away from the nucleus, their freedom of movement decreases, resulting in a decrease in the electric conductivity of the element.
Bye,Sandro
Here is another possible explanation.
The electrical conductivity of alkali metals decreases throughout the group when the electrons move away from the nucleus, as they lose their mobility and are less involved in the transport of electrical charge.
Electrons with higher energy can be transferred easily from atom to atom when closer to the nucleus, enabling a greater electrical conductivity. At the same time, as the electrons move away from the nucleus, their freedom of movement decreases, resulting in a decrease in the electric conductivity of the element.
Bye,
I would like to clarify the previous explanation to avoid any possible misunderstandings. The electrical conductivity of alkali metals decreases as the radius of the atom increases, as the valence electron moves away from the nucleus. This greater distance weakens the electrostatic attraction between the nucleus and the outer electron, which is less bound to the nucleus. However, increasing the distance between the nucleus and the valence electron reduces the mobility of the electrons within the metal lattice.
In the lower part of the group, an increase in the atomic radius and enhanced electron-electron repulsion reduce the mobility of electrons, even with weakened attraction to the nucleus. This reduces the conductivity.
Please read the chapter "Physical Properties" here: Alkali Metals
Bye,
Sandro
(edited 1 year ago)
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