Why Does Metallic Radius Decrease Across a Period in Transition Metals?

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The discussion centers on the confusion surrounding the behavior of metallic radii in transition metals. The original poster questions the trend of decreasing metallic radii across a period, suggesting that if metallic radii are defined as half the distance between two metal atoms, increased bonding should lead to smaller radii. However, responses clarify that the effective nuclear charge (Zeff) increases across a period, resulting in a stronger attraction between electrons and the nucleus, which actually leads to a decrease in metallic radii. The conversation also touches on the distinction between metallic and ionic radii, emphasizing that metallic radius is influenced by the strength of metal-metal bonds and the nature of conduction electrons. Additionally, there is a query about why metallic radii increase down a group, with the implication that greater overlap between metal atoms should reduce radii, indicating a need for further clarification on this trend.
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I am so confussed..

Talking about transition metals, in the book it says that the general trend in a period is for the metallic radii to decrease due to increase of Zeff. But I don't think this makes sense.

I think: we are talking about metallic radii not IONIC! If its metallic, then the radii would be half the distance between the two metals. hence, the greater bonding, the smaller de radii. Hence, as the period goes by and the orbitals become more contracted, less bonding, GREATER RADII!

why am i wrong?
please help!
 
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Well that's the thing!
metallic radius is defined as half of the distance between two metals in a metal bond.
ionic radius on the other hand is different. that's why i think that talking about zeff should be to explain the ionic radius not the metallic radius.

metallic radius has to be related to the strenght of the m-m bond.
 
Why do you think that more contracted orbitals are less bonding? It is the other way round!
Furthermore, at least main group metals are well described as ionic cores surrounded by nearly free conduction electrons, the distance of the atoms being dictated by the radii of the ionic cores.
 
DrDu said:
Why do you think that more contracted orbitals are less bonding? It is the other way round!
Furthermore, at least main group metals are well described as ionic cores surrounded by nearly free conduction electrons, the distance of the atoms being dictated by the radii of the ionic cores.

oh god yes.. hadn't realized the first part :)
okay, but then, why does the metallic radius increase as the group goes down? as the group goes down the overlap between metals is greater and hence should be a smaller metallic radii!

didn't quite get the last part of your comment .. :)
 

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