EK GChem #24

[msw27]

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Q: Aluminum has only one oxidation state, while chromium has several. Which of the following is the best explanation for the difference?

A: Electrons in the d orbitals of Cr may or may not be used to form bonds.

The explanation states that since Cr has more oxidation states than Al, Cr requires variability in number of bonds formed. Cr has electrons in the orbitals of the 2p subshell, but these are core electrons and not used for making bonds. Cr has 6 valence electrons, 5 of which are in the orbitals of the 3d shell.

How does the oxidation state determine the number of bonds? I understand that each ion wants a noble gas configuration and will use it's valence electrons to bond (hence the d orbitals allowing for more or less bonds in chromium). I've seen Al with four bonds and no charge before, so I don't understand the concept behind this question. Can anyone help?

 

[161927]

Q: Aluminum has only one oxidation state, while chromium has several. Which of the following is the best explanation for the difference?

A: Electrons in the d orbitals of Cr may or may not be used to form bonds.

The explanation states that since Cr has more oxidation states than Al, Cr requires variability in number of bonds formed. Cr has electrons in the orbitals of the 2p subshell, but these are core electrons and not used for making bonds. Cr has 6 valence electrons, 5 of which are in the orbitals of the 3d shell.

How does the oxidation state determine the number of bonds? I understand that each ion wants a noble gas configuration and will use it's valence electrons to bond (hence the d orbitals allowing for more or less bonds in chromium). I've seen Al with four bonds and no charge before, so I don't understand the concept behind this question. Can anyone help?

compare the electron configurions of Al and Cr
Cr is one of those elements that puts an unpaired electron from its d orbital into its closest energy s orbital, so that both orbitals have fully paired electrons

 

[cleopetra]

Q: Aluminum has only one oxidation state, while chromium has several. Which of the following is the best explanation for the difference?

A: Electrons in the d orbitals of Cr may or may not be used to form bonds.

The explanation states that since Cr has more oxidation states than Al, Cr requires variability in number of bonds formed. Cr has electrons in the orbitals of the 2p subshell, but these are core electrons and not used for making bonds. Cr has 6 valence electrons, 5 of which are in the orbitals of the 3d shell.

How does the oxidation state determine the number of bonds? I understand that each ion wants a noble gas configuration and will use it's valence electrons to bond (hence the d orbitals allowing for more or less bonds in chromium). I've seen Al with four bonds and no charge before, so I don't understand the concept behind this question. Can anyone help?

Cr and Cu are 2 exceptions when filling of electrons is considered. Half filled or fully filled orbitals are more stable. Cr has 24 electrons . if we fill electrons according to their energy level we find that 4s should be filled first (it has lower energy) than 3d. So Cr should have electronic configuration 4S2,3d4. But it has electronic configuration 4S1,3d5. (this is because when d orbital has 5 electrons, it is half filled and hence more stable) because of this configuration 4s electron as well as 3d electrons are available for bonding. That's y it shows more than one valency.( same case is with the Cu which has total 29 electrons and it's 3d orbital is fully filled and has configuration 4S1,3d10)

 

[msw27]

Thanks to both of you, I appreciate it🙂

 

[SKation]

Hello,
I was slightly confused about this question as well. Does this mean that when the d-orbitals are stable (taking the electron from the s subshell) that then Cr won't use the electrons to make bonds because it is stable however if it dosent take the electron then it will use its d-electrons to make bonds?

Thanks, 🙂