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I am confused about the zig-zag pattern of metalloids in the periodic table. Why are metalloids arranged in a zig-zag line? Can anyone answer my question?

Pritt says Reinstate Monica
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Eddy Kwong
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2 Answers2

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In addition to Pritt Balagopal's answer, in which he has clarified the trends in metallic character across the Periodic Table, I would also like to explain why the metalloids occur in a zig-zag fashion.

Firstly, I would like to again clarify that it is possibly a coincidence that the metalloids start from boron, not carbon or any other non-metal in that period. My guess could be the start of electron occupation of the p subshells. Note that boron has one electron in its p subshell. Thus, its chemical properties start to change to become more non-metallic in nature.

Diagonal relationships is a common occurrence in the Periodic Table. However, it is often used to describe the relationship between two elements which are diagonal to each other, not a whole line of them. Thus, I would like to clarify again that this is just my conjecture, not what is the true reason. But I believe this should be part of the correct explanation as it is logically sound.

enter image description here

This site offers a more in-depth explanation as to why diagonal relationships occur: https://chem.libretexts.org/LibreTexts/University_of_Denver/Chem_2132%3A_Chemistry_of_the_Elements/Unit_3%3A_Descriptive_Chemistry/09%3A_Building_a_Network_of_Ideas_to_Make_Sense_of_the_Periodic_Table/9.3%3A_The_Diagonal_Effect

In short, the diagonal relationships are based on two effects: the increasing effective nuclear charge across a period and the decreasing effective nuclear charge down a group. Effective nuclear charge increases across a period because the number of shielding electrons in the inner shells is constant while there are additional protons in the nucleus of the atoms of the elements across the period. Effective nuclear charge decreases down the group as there is an addition shell of shielding electrons from one element to the next in the group. (These are similar to the trends in metallic character pointed out in Pritt Balagopal's answer.)

These two competing effects cancel each other out and thus, chemists believe that the chemical properties of elements in a diagonal should be similar. The image shows some examples.

Tan Yong Boon
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Well, the answer is quite simple:

Elements on the periodic table tend to follow this trend:

  • Metallic character increases as you move down a group: This is because every step you move down the group, an extra shell of electrons is added, along with a bunch of protons that increase nuclear attraction. The extra shell factor plays the dominant role, making the outermost electron easier to remove, thus attributing to increased metallic character.

  • Metallic character decreases as you move across the period along the right: As you move along the period, one extra electron is added to the outermost shell, and a proton is added to the nucleus. Since the extra electron doesn't considerably change the location of the shell, the extra proton brings the shell considerably closer to the nucleus, making the outer electrons more tightly bound, decreasing the metallic nature.

Keep this in mind.

enter image description here

Start with boron, you see that all thats below it are metals. Carbon is a non-metal, Silicon and Germanium are metalloids, and the rest below are metals. I think now you can see the relationship here. Going right from a metalloid gives you a non metal. To find another metalloid, you gotta look down. What you get in the end is a diagonal cluster of metalloids.

Pritt says Reinstate Monica
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    This answer would be improved with some explanation of why metallic character behaves as it does - that is, why does metallic character increase as you move down a group, and why does it decrease as you move across a period to the right. – R.M. Jun 21 '17 at 15:01
  • You are not explaining the trend. You merely describing the trend. – Tan Yong Boon Jun 21 '17 at 15:26
  • It's done @R.M. – Pritt says Reinstate Monica Jun 21 '17 at 15:45
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    What I meant by my previous comment is that what you are explaining is the trend in metallic character across the Periodic Table and not the diagonal trend in the metalloids. Therefore, the explanation you have provided explains why do metalloids exist and why they are found at that position in the table but not why they follow a diagonal trend. – Tan Yong Boon Jun 24 '17 at 02:58
  • @TanYongBoon read my last paragraph. – Pritt says Reinstate Monica Jun 24 '17 at 02:59
  • Your last paragraph describes the trend. You do not seem to be explaining, using chemical reasons, why the metalloids occur in a zig-zag fashion. I would think an answer to this question should also feature "diagonal relations in the Periodic Table". – Tan Yong Boon Jun 24 '17 at 03:02
  • Perhaps, the link wasn't made clear enough. But now that you've pointed it out, it does make sense. I didn't ask for chemical reactions, but chemical reasons. I guess the reasons you provided are sufficient, after clarification. – Tan Yong Boon Jun 24 '17 at 03:31
  • But if you think about it, what is explained is why it occurs in a diagonal, not zig-zag fashion. Note that zig-zag means to include the element which is below one element and to the left of the other. I seemed to have not realised this until just recently. So I have missed this out in my answer as well. – Tan Yong Boon Jun 24 '17 at 03:37