Atomic Radius

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Norah Gidanian 3D
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Atomic Radius

Postby Norah Gidanian 3D » Fri Nov 06, 2020 9:48 am

Can someone explain why the atomic radius decreases as you move across a period? If there are more electrons shouldnt electron-electron repulsion push them farther away, making the radius larger?

Alexandra Ahlschlager 1L
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Re: Atomic Radius

Postby Alexandra Ahlschlager 1L » Fri Nov 06, 2020 9:53 am

The atomic radius decreases as you go across a period because more protons are being added to the nucleus as you go across. With every proton added, the attraction between the electrons and protons grows, bringing the electrons closer and closer to the nucleus. Therefore, the atomic radius gets smaller. Hope this helps!

Charlotte Adams 1A
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Re: Atomic Radius

Postby Charlotte Adams 1A » Fri Nov 06, 2020 11:00 am

As you move towards the right of the periodic table the atomic number increases which gives the amount of protons in the nucleus, and a more positive nucleus has a greater pull on the electrons, thus decreasing the atomic radius.

SLai_1I
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Re: Atomic Radius

Postby SLai_1I » Fri Nov 06, 2020 11:04 am

As you move across a period, more protons are being added to the nucleus, increasing the atomic number. This makes the nucleus more positive, giving it a stronger pull on the valence electrons, decreasing the atomic radius.

Emma Strassner 1J
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Re: Atomic Radius

Postby Emma Strassner 1J » Fri Nov 06, 2020 2:23 pm

The radius decreases across the period because the effective nuclear charge increases as you go across. This causes greater attraction to electrons that pulls them in closer to the nucleus, resulting in a smaller radius.

Yu Jin Kwon 3L
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Re: Atomic Radius

Postby Yu Jin Kwon 3L » Fri Nov 06, 2020 2:36 pm

Everyone above explained why the atomic radius decreases as you go right on the PT. To explain when electron-electron repulsion will occur and how that can impact the radius: when you go down the periodic table, you add more shells, meaning you have much more electrons to shield the positive charge of the nucleus. Firstly, the sheer amount of electrons you now have (as you go down the PT) means that there are more negative charges repelling away from each other, causing the radius to increase. Secondly, the electrons closer to the nucleus (as I mentioned before) shield the pull of the nucleus, meaning more electrons will stray further away from the nucleus, causing a larger radius as well.

I hope this helps in giving a different view of when electron-electron repulsion makes the radius larger :D

Maya Johnson 2a
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Re: Atomic Radius

Postby Maya Johnson 2a » Fri Nov 06, 2020 2:38 pm

When you move across the periodic table, the atomic radius gets smaller because with more protons, there is a greater pull on the electrons. Ultimately, this results in a smaller atomic radius.

Joseph_Armani_3K
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Re: Atomic Radius

Postby Joseph_Armani_3K » Fri Nov 06, 2020 2:51 pm

As we go across a period, the number of protons increase one by one, which would result in a progressively higher electrostatic attraction

Katie Nye 2F
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Re: Atomic Radius

Postby Katie Nye 2F » Fri Nov 06, 2020 4:07 pm

As you go across a period, there are more protons in the nucleus. Because of this, the attraction to the electrons is stronger so they are pulled in tighter, making the atom smaller. My high school teacher always described it as "Coulombic attraction" and it increases as protons are added to the nucleus.

kateraelDis1L
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Re: Atomic Radius

Postby kateraelDis1L » Fri Nov 06, 2020 5:30 pm

As nuclear charge increases there is greater attraction. Keep it simple ;)

Colin Squire 3C
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Re: Atomic Radius

Postby Colin Squire 3C » Fri Nov 06, 2020 6:41 pm

There are more protons in each element as we move to the right in the periodic table. This means that the pull they have on the electrons are stronger, which then the radii are going to get increasingly smaller.

Sofia Lombardo 2C
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Re: Atomic Radius

Postby Sofia Lombardo 2C » Fri Nov 06, 2020 7:26 pm

Atomic radius decreases as you go across a period because the protons increase and shielding remains constant. Even though you are adding electrons, since the shielding remains constant, the effective nuclear charge is able to have a stronger pull on the electrons, thus making the atom smaller.

Navdha Sharma 3J
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Re: Atomic Radius

Postby Navdha Sharma 3J » Fri Nov 06, 2020 8:03 pm

All the elements in a period have the same number of shells(just the number of valence electrons vary). But, the number of protons across a period increases, and so the effective nuclear charge increases which causes the size to decrease across a period.

Morgan Gee 3B
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Re: Atomic Radius

Postby Morgan Gee 3B » Sat Nov 07, 2020 12:50 am

While electrons increase and the repulsion causes the radius to increase slightly, protons are also increasing. The positivity of the protons cause the electron cloud to shrink, resulting in a decrease in atomic radius as you move across a period.

Binyu You
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Re: Atomic Radius

Postby Binyu You » Sat Nov 07, 2020 1:30 am

The atomic radius decreases when going across the period because there are more protons when moving to the right in the periodic table. As proton is added, the attraction grow, which makes the electrons tightly packed, thus making atomic radius smaller.

Renny_kim_2G
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Re: Atomic Radius

Postby Renny_kim_2G » Sat Nov 07, 2020 9:42 am

The more pairs of electrons and protons you have, the more attraction there is. Therefore, as you move right, these pairs increase and the radius gets smaller.

Nhu Pham-Dis3G
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Re: Atomic Radius

Postby Nhu Pham-Dis3G » Sat Nov 07, 2020 1:41 pm

It is because across a period, effective nuclear charge increases as electron shielding is maintained. Higher effective nuclear charge = greater attractions to the electrons = electron cloud pulled closer to nucleus = smaller atomic radius.

Brandon Le 3C
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Re: Atomic Radius

Postby Brandon Le 3C » Sat Nov 07, 2020 2:02 pm

As you move across a period from left to right, the protons of the atom increases. Because of this, the attraction between the electrons and the nucleus becomes stronger, therefore making the atomic radius smaller as the attraction squeezes it together.

Leyla Anwar 3B
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Re: Atomic Radius

Postby Leyla Anwar 3B » Sat Nov 07, 2020 10:27 pm

Does the atomic radius being smallest at the top right have anything to do with the more complete octet those elements have? Because as you move down the radius increases but it has extra valence electrons that need to be balanced. I guess I'm just wondering if the octet has anything to do with it.

Jeremy Wei 2C
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Re: Atomic Radius

Postby Jeremy Wei 2C » Sun Nov 08, 2020 12:49 am

Hi, the atomic radius in the top right is related to the complete octet of the elements because as the octet starts to fill up, there are more valence electrons for the protons in the nucleus to interact with, the attraction being stronger.

Jonathan Banh 1G
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Re: Atomic Radius

Postby Jonathan Banh 1G » Sun Nov 08, 2020 3:49 am

Atomic radius decreases as you go across a period (left to right) because of how electron shielding remains constant while effective nuclear charge increases with the addition of protons. As a result, this increase in protons causes the attraction between the nucleus and electron cloud to increase, meaning the electron cloud will be pulled inwards, making it tighter and smaller. Thus, this explains how atomic radius shrinks in size.

Mackenzie Stockton 2H
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Re: Atomic Radius

Postby Mackenzie Stockton 2H » Sun Nov 08, 2020 11:39 am

As you move right across a period, the number of protons increases (positive charge). This positive charge "pulls in" the negative electrons, so the electrons are closer to the nucleus (where the protons are). Because the electrons are more pulled closer to the nucleus as the number of protons increases, atomic radius decreases across a period.

Danielle DIS2L
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Re: Atomic Radius

Postby Danielle DIS2L » Sun Nov 08, 2020 4:28 pm

The atomic radius decreases across the periodic table because there are more protons being added to the nucleus where there would be less electron electron attraction thus making the nucleus of an atom smaller.

Chris_Butler_1A
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Re: Atomic Radius

Postby Chris_Butler_1A » Sun Nov 08, 2020 4:43 pm

I apologize if this has already been asked but because neutrons have a neutral charge, and thus they do not "pull-in" the electrons in the orbitals, can we say that they don't affect the atomic radius? For example, Carbon-12 and Carbon-13 would have the same atomic radius?

Tobie Jessup 2E
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Re: Atomic Radius

Postby Tobie Jessup 2E » Sun Nov 08, 2020 9:30 pm

As your move across the periodic table, more protons are added to the nucleus and therefore there is a stronger positive charge that pulls the electrons closer to the nucleus.

Andy Hernandez
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Re: Atomic Radius

Postby Andy Hernandez » Sun Nov 08, 2020 9:53 pm

As we go across a period, the number of protons increase one by one, it results in a progressively higher electrostatic attraction

AlbertGu_2C
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Re: Atomic Radius

Postby AlbertGu_2C » Sun Nov 08, 2020 10:14 pm

More protons equals more positive charge to attract electrons

Sarah Huang 3A
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Re: Atomic Radius

Postby Sarah Huang 3A » Sun Nov 08, 2020 10:29 pm

Norah Gidanian 3J wrote:Can someone explain why the atomic radius decreases as you move across a period? If there are more electrons shouldnt electron-electron repulsion push them farther away, making the radius larger?


Hi Norah! I originally had the same misconception as well! However, the reason why atomic radius decreases as you move across a period is because as you go along, the elements have a higher nuclear charge. For example, from carbon to nitrogen to oxygen, the amount of protons goes from 6 to 7 to 8. With an increase in protons, there is an increase in nuclear charge, and since there is usually one electron per proton, that is why we see a neutral charge, but even though there is an equal ratio of protons to electrons, protons carry a greater charge, so they create a stronger pull. The stronger pull results in the electrons becoming more tightly held together, closer to the nucleus, thus decreasing the atomic radius.

The electron-electron repulsion applies more when you add electrons to the same element. For example, if you have N and N-, the extra electron in N- generates greater electron-electron repulsion, thus increasing the atomic radius. The nuclear charge stays the same since the amount of protein has not changed. So, if you were to order N, N-, and N+ from largest to smallest atomic radius, what would you get?

If you got N-, N, N+, you are absolutely correct! You should already understand why N- is greater than N, but N+ is the smallest because it lost an electron, so there is a decrease in electron-electron repulsion amongst the remaining electrons and the nuclear charge pulls them even closer, thus decreasing the size of N+'s atomic radius in comparison to N.

I hope that helps!

Jaden Kwon 3C
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Re: Atomic Radius

Postby Jaden Kwon 3C » Sun Nov 08, 2020 10:42 pm

Going across a period nuclear charge increases due to the addition of more protons while electron shielding remains constant which causes a causes electrons to be pulled closer to the nucleus making the atomic radius smaller.

Brian Nguyen 2I
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Re: Atomic Radius

Postby Brian Nguyen 2I » Sun Nov 08, 2020 10:52 pm

It decreases as you move across a period because the atomic number increases. When the atomic number increases, the amount of protons increase. There is more of a positive charge present, increasing the attraction between the electrons and protons, thus decreasing the space between the electrons and protons. This decreases atomic radius.

Nick Saeedi 1I
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Re: Atomic Radius

Postby Nick Saeedi 1I » Sun Nov 08, 2020 11:01 pm

The number of protons increases as you move across a period so there is a stronger pull on the electrons making the atomic radius smaller.

LovepreetSran_3H
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Re: Atomic Radius

Postby LovepreetSran_3H » Sun Nov 08, 2020 11:02 pm

As you move across the period, the atomic number increases, thus more protons are present. This increases attraction causing the atomic radius to decrease.

rhettfarmer-3H
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Re: Atomic Radius

Postby rhettfarmer-3H » Sun Nov 08, 2020 11:35 pm

Atomic radius decreases as we move to the right of the periodic table because more electrons we have a closer outer shell because of the attraction of the inner nuclear charge is increasing at the same right while the shielding of electrons is remaining the same so there is a short radius by a stronger force pulling them in despite more electrons.

Ke Huang 2G
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Re: Atomic Radius

Postby Ke Huang 2G » Sun Nov 08, 2020 11:39 pm

As you move to the right of the periodic table, the radius decreases because electrons are attracted to the nucleus as the nucleus has more positive charges.

Chris_Butler_1A
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Re: Atomic Radius

Postby Chris_Butler_1A » Sun Nov 15, 2020 5:29 pm

I apologize if this has already been asked but I had a little confusion in regards to how Atomic Radius is calculated in ionic bonding. From what I understand, the Atomic Radius is half the distance from the center of a neighboring atom. How does this affect our ability to measure the radii of say NaCl where Cl- has a higher electronegativity than Na+?

Alex Benson
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Re: Atomic Radius

Postby Alex Benson » Sun Nov 15, 2020 9:20 pm

Hi! The atomic radius decreases as you go down a period because the nucleus increases in size. Although there is more electron-electron repulsion I believe that this force is overpowered by the strength of the nucleus.

Gustavo_Chavez_1K
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Re: Atomic Radius

Postby Gustavo_Chavez_1K » Sun Nov 15, 2020 11:12 pm

Yeah so although there are more electrons we must keep in mind that this means that there are also more protons. So, the more protons there are in the nucleus then the more the nucleus pulls on the electrons. This ultimately decreases the radius of the atom.

Brandon McClelland3L
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Re: Atomic Radius

Postby Brandon McClelland3L » Sun Nov 15, 2020 11:20 pm

As you move across a period there are more protons, increasing the effective nuclear charge. However, the reasoning you stated is why ions of the same molecule have different atomic radii.

Geethika Janga 1L
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Re: Atomic Radius

Postby Geethika Janga 1L » Sun Nov 15, 2020 11:27 pm

As you move across the period, although the total number of electrons increase, they are being added to the same shell. Along with the number of electrons, the number of protons increases too the effective nuclear charge will be greater moving across the period. The electrons will experience a greater attraction to the nucleus and as a result, the atomic radius decreases.


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