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Questions tagged [atomic-radius]

For questions about the atomic radius - a measure of the size of an atom, usually the mean or typical distance from the center of the nucleus to the boundary of the surrounding "cloud" of electrons.

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1answer
4k views

Why is the radius of the caesium cation smaller than that of the chloride anion?

I am currently studying the structures of ionic compounds and how we can use radius ratios to predict the possible arrangement of ions in the lattice. My book mentions that the cation to anion radius ...
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Does electron shielding increase or stay constant moving LEFT to RIGHT across a period?

Does electron shielding increase or stay constant moving left to right across a period? I have read about both, and I just want to know which one is right. I believe that electron shielding remains ...
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Trend in atomic radius for noble gases

In an exam, we were given the following graph and asked to explain why the slope of the change in r vs. Z changes dramatically at a point along the curve. I understand that the d block causes the ...
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1answer
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van der Waals coefficients for helium and neon

The values of the coefficient $b$ for helium and neon are $$\begin{array}{cc} \hline \text{Element} & b\text{ / }\mathrm{dm^3\ mol^{-1}} \\ \hline \ce{He} & 2.38 \times 10^{-2} \\ \ce{Ne} &...
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653 views

Atomic radius definition disproved - Bohr's model to Schroedinger's wave equation

According to the Schrödinger wave equation, Bohr's model of atomic orbitals is disproved and a new formalism that describes atomic orbitals is introduced. It follows that the definition of ...
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Why is the ionic radius of Al(3+) smaller than that of Li+?

I was examining the ionic radii of some ions from this site for a school assignment. I noticed a weird anomaly in the ionic radius of $\ce{Li+}$ as compared to that of $\ce{Al}^{3+}$. The ionic ...
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0answers
45 views

Co vs Rh atomic radius

Why is the empirical atomic radius for both Co and Rh 135 pm, the same? Source
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2answers
886 views

Why is there a discrepancy among sources on the atomic radius of some elements?

My book says the atomic radius of gallium is less than that of aluminium, but I found out different atomic sizes on different sites. For example, this says gallium is 136 pm and aluminium is 118 pm, ...
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1answer
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Range of distance for Van der Waals force

Is there any range of distance between the nuclei of the atoms (in Angstrom, say between 4 to 12 Angstrom) within which there will be an occurrence of Van der Waals force (attraction) between them? ...
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445 views

The ionic radius of aluminium(III) vs. the covalent radius of neon?

I was wondering if it is a valid comparison to look at the ionic radius (noble-gas-like configuration) of a metal and the covalent radius of a noble gas. Specifically, $\ce{Al^{3+}}$ and $\ce{Ne}$. ...
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1answer
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Comparing radii in lithium, beryllium, magnesium, aluminium and sodium ions

Apparently the of last four, $\ce{Mg^2+}$ is closest in radius to $\ce{Li+}$. Is this true, and if so, why would a whole larger shell ($\ce{Mg^2+}$) be closer in radius to $\ce{Li+}$ than its ...
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1answer
972 views

Why is it easier to determine the radius of inert/noble gases?

My textbook says it is possible to determine the atomic radius of the inert gases like He, Ne, Ar etc because they roam freely and are incapable of forming bonds. However it is very difficult to find ...
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1answer
4k views

Calculate the radius of an Ag atom

The question I have been given is: Silver atoms in a metallic lattice only fill up $88\,\%$ of the space ($12\,\%$ is empty). The density of silver is $10.5\ \mathrm{g\cdot cm^{-3}}$. Assuming that ...
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1answer
4k views

Ionization energy and Electron Affnity

Which of the following statements correctly interprets the relationship between ionization energy, atomic radius Electron affinity when comparing two atoms. The correct choice as per my instructor ...
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1answer
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Meaning of the 1s orbital diagram

I'm a little confused about the interpretation of the 1s orbital diagram. I know that the outer boundary is where the wave function of the 1s orbital has a constant value, which means means there's a ...
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1answer
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How do I find the diameter of an aluminum atom from its density and atomic mass? [closed]

I am supposed to find the diameter of an aluminum atom using data given by my teacher. Here is the data: \begin{array}{cc} \text{Density of Aluminum}& \pu{2.70 g/cm3}\\ \text{Atomic Mass of ...
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281 views

Why do some elements such as polonium not follow the trend of decreasing atomic radius?

Most of the periodic table follows the trend of increasing radius as you move down a family and decreasing radius as you move across a period. Why is this trend not observed for polonium?
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Variation in atomic sizes in the transition elements

From left to right across a period, effective nuclear charge increases in the transition series, just like in the p block, and so atomic size decreases. Here the electrons are being added to the d ...
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How would I find an apporpriate dopant element for a lattice

I am trying to figure how would I go about finding a dopant element that would fit in a copper lattice? I already have the data for the atomic dimensions and structure (available below), however how ...
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2answers
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Why are the atomic radii of iron, cobalt, nickel, and copper almost the same?

We have to select the set of elements which will have almost the same atomic radii: $\ce{O, S, Se, Te}$ $\ce{Li, Be, B, C}$ $\ce{Fe, Co, Ni, Cu}$ I googled the atomic radii of the third set and ...
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950 views

Why are there drastic changes sometimes in radius of isoelectronic ions?

$\ce{S^{2-}}$, $\ce{Cl-}$, $\ce{K+}$, and $\ce{Ca^{2+}}$ each have the same number of electrons. Their effective ionic radii are 182, 181, 138, and 100 picometers, respectively, and the number of ...
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1answer
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Comparison of atomic radii

My teacher told me that Neon has a larger atomic radius than Fluorine.I am of the understanding that it is merely a consequence of the way we define the atomic radius and that we use Van der walls ...
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1answer
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“Crystal radius” vs “Ionic radius”

What is the difference between crystal radius and ionic radius? For $\ce{NaCl}$ for example the ions combine to a crystal, and I would have guessed they are equal. But I then found an example of data, ...
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Why is the atomic radius of krypton smaller than that of potassium?

A potassium atom comprises 19 protons and 18 core electrons. Those electrons screen 18 protons worth of Coulomb force. Therefore, there is one proton worth of Coulomb force attracting the valence ...
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1answer
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Variation in atomic radii of elements in different blocks?

If we look at the values for the atomic radii (look at the table here), we can see that they rapidly decrease across the period initially. Looking at the second period, The graph is pretty steep ...
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1answer
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Ionic bond and ionic radii in FeS

Which of the following statements is true regarding an ionic bond in $\ce{FeS}$? Iron atoms gain electrons and sulfur atoms lose electrons. Iron and sulfur ions bond by ...
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1answer
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The explanation on atomic size

I always receive two type of explanation for the decreasement of atomic size for elements across the period. Explanation according to proton number This explanation is from my teacher. The proton ...
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1answer
126 views

Atomic number $Z$

If electrons were spin-$\frac {3}{2}$ instead of spin-$\frac {1}{2}$ , what would be the atomic number $Z$ for the first noble gas ?
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409 views

What radius best represents reaction distance?

Molecules must be within a certain distance for a reaction to begin as well as satisfying a myriad of other factors. Whilst the exact distance varies from reaction to reaction, is their any distance/...
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323 views

Interaction radius of a molecule

What is the most commonly used radius of an atom or molecule to describe the area that must touch another area of another molecule for the two to react. Is there one radius that always works or does ...
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1answer
404 views

Why does the “gap” between atomic radii get smaller down the periodic table?

The question asks: why is the difference in atomic radii between $\ce{K}$ and $\ce{Na}$ larger than the difference in atomic radii between $\ce{Cs}$ and $\ce{Rb}$? I do have some kind of notion that ...
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3answers
28k views

Why does Mg2+ have the ionic radii bigger than Ca2+

If they were atoms, $\ce{Mg}$ should have a smaller radii. How does this change?
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1answer
517 views

Is it possible to calculate atomic radius with electron configuration?

I need to know whether is it possible to calculate the atomic radius according to the number of electrons and electron configuration. Or is there any way to calculate the atomic radius using common ...
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0answers
923 views

How to determine relative size of polyatomic ions?

How would you determine the size of a polyatomic ion? For example when determining which ion is bigger, $\ce{NH2-}$ or $\ce{I-}$, what would you use to determine the size difference? I know that $\...
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2answers
900 views

How to list elements according to their radius? For example Ag, Cd, Au Can you check the accuracy of these sentences I've created?

I've asked a similar question before, but now I want to find out the real rule. Pleas tell me if my interpretation is correct: Cd, Ag , Au (increasing ray order). This happens because although we know ...
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2answers
100 views

How do I list these elements according to their radius?

$\mathrm{Z=33,\ Z=37,\ Z=9,\ Z=31}$ Since we shouldn't look at the periodic table, I found their groups and periods, what should I do next?
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2answers
325 views

XRD-Shorter distance between planes than actual radius of atoms/or cell parameter

I'm solving problems related to X-ray diffraction, and I get these results which apparently are correct. My question may be dumb, but I just can't see how the interplanar distance might be shorter ...
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1answer
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Which is the bigger ion, F- or O-?

Well, according to the proton-electron ratio $\ce{O-}$ should be bigger than $\ce{F-}$ What about the charge/electron density in $\ce{F}$? Will it not affect the size of the atom of $\ce{F-}$?
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1answer
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How can we measure the atomic radius of an atom?

The definition of atomic radius is half the average internuclear distance of an atom. But many times I've been told that it is not possible to handle a single atom. Thus how can we measure the ...
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1answer
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Can ionic and atomic radii be compared?

Can ionic and atomic radii be compared? For example, this is a common problem in some intro chem courses: Rank the following from smallest to largest: sodium ion, magnesium ion, neon, fluoride, ...
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2answers
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Finding orbit radius using the Bohr model and Rydberg equation

To start with its a homework problem, quite lengthy. A particle of mass equal to 208 times the mass of an electron moves in a circular orbit around a nucleus of charge $+3e$. Assuming the Bohr ...
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2answers
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Atomic radii of Sc, Ti, Fe, and Co

The atomic radius of Sc is $\pu{162pm}$, Ti is $\pu{147pm}$, $\ce{Fe}$ is $\pu{126pm}$, and that of $\ce{Co}$ is $\pu{125pm}$. The electronic configuration of $\ce{Fe}$ is $\ce{[Ar] 3d^6 4s^2}$, and ...
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1answer
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Van der Waals Radius clarifications

I just read about van der Waals radius and had some questions about it. Would it be correct to say that in general, van der Waals radius decreases as we move from left to right in the periodic table? ...
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1answer
186 views

How do we know the size of atoms in body centered cubic system?

I'm told that in the normal cubic system there are $\frac18$ of an atom at each corner and these atoms' radius are such that $a = 2r$ ($a$ is the lattice constant, $r$ radius of an atom). In bbc (...
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3answers
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Is it possible to compress an atom to infinite density? [closed]

I know, by nature, normally atoms are stable. But I wonder, if it is possible to compress an atom, say the Hydrogen atom, to infinite density by applying external force? After all, electrons and ...
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For which pair of species is the difference in radii the greatest?

For which pair of species is the difference in radii the greatest? (A) $\ce{Li}$ and $\ce{F}$ (B) $\ce{Li+}$ and $\ce{F^-}$ (C) $\ce{Li+}$ and $\ce{O^2-}$ (D) $\ce{O^2-}$ and ...
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1answer
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Ca and Mg hydrated radius in clay flocculation

Ca has an atomic radius of $197\mathrm{~pm}$ and a Pauling electronegativity of $1.00$. Mg has an atomic radius of $197\mathrm{~pm}$ and a Pauling electronegativity of $1.31$. Since Mg is smaller ...