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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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Gap in ionic radii

The above picture was shown in a presentation by my prof in inorganic chem as we were discussing ionic radii more in depth (all in pm). These are all isoelectronic radii. Notice the sudden leap in ...
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Lanthanoid Contraction

Why is the radius of Europium so unusually high and out of the general trend ? Moreover, at different sources I am getting different values of radii. In some (e.g., Wikipedia) the radii are following ...
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1answer
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Radius with Bohr model [closed]

$$r_n = \left(\frac{h^2}{4\pi^2me^2}\right)\times\frac{n^2}{Z} $$ Would I be able to calculate the radius of sodium ion ($\ce{Na+}$) with the help of the above Bohr atomic model formula?
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Why does the beryllium 2+ ion have a larger radius than a helium atom?

$\ce{Be^2+}$ has an ionic radius of $\pu{45 pm}$, while $\ce{He}$ has a radius of only $\pu{31 pm}$. If they are isoelectronic (they both have two elections in the $\mathrm{1p}$ orbital), and $\ce{Be}$...
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Why are the Covalent Radii of Ruthenium and Osmium So Similar?

Osmium and Ruthenium have covalent radii 144 and 146 respectively (according to Wikipedia). How are these values so similar when Osmium has 32 more electrons, with another filled p, s, and f orbital ...
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1answer
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How am I supposed to answer this? [closed]

First the question gives no units or that these are covalent radii or what, so I assume they are in nanometers and assume an atomic radius. I check my periodic table app and it says a 92pm atomic ...
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1answer
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How to get ionic radii for coordination number 12?

I am studying $\ce{ABX3}$ perovskites, and I would like to calculate Goldschmidt tolerance factors for them. The $\ce{A}$ sites in these materials have a coordination number $12$. The Shannon's ...
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Which has a greater atomic radius, Cl- , K+ , S-2 , Ca+2 , Ar? [duplicate]

How can I know that? I only know that while we going to the right side at the table so the radius is decreasing. And while we going down, so the radius is bigger. But how can I check that radiuses ...
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Mismatch in the trends of atomic size and atomic radius

In the periodic table, the atomic radius decreases as we move from left to right in a period. However, the atomic volume should also decrease as a result of the decrease in atomic radius, as volume is ...
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Radial probability curve [closed]

Can somebody give me a clue on how to solve the question in the picture for me given below
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1answer
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Comparing size of ions lithium, gallium ions

How is the size of $\ce{Li+}$ ($\pu{0.68}$) larger than $\ce{Ga^3+}$ ($0.62$)? This is very difficult for me to understand why they say that size of Li+ with 3 protons and just 2 electrons should be ...
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For a given period, why is the boiling point of the halogen greater than that of the noble gas?

The boiling point of bromine, a halogen, is $\pu{58.8^\circ C}$, while the boiling point of krypton, the noble gas in the same period as bromine, is $\pu{-153.4 ^\circ C}$. I thought that the larger ...
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What is the difference between the mean radial distance and the most probable radial distance of an orbital?

I was reading JD Lee's Concise Inorganic Chemistry and it has given some values of mean radial distance which is increasing from s to p to d orbital. I had earlier read that the most probable radial ...
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1answer
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What is the atomic radius of chlorine?

I'm trying to study for chemistry and there's a question in my book about identifying an element based on its atomic radius. But when I looked up the value for chlorine, I found different answers from ...
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Is significant figure important for atomic radius calculations? [closed]

Is significant figure important for atomic radius calculations? Calculate the radius of a vanadium atom, given that V has BCC crystal structure, a density of $\pu{5.96 g/cm^3}$, and an atomic ...
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Why is the difference between atomic radii of Na and K greater than that of Rb and Cs?

I am aware that this question has already been asked here: Why does the "gap" between atomic radii get smaller down the periodic table?. However, I was wondering if there is a way to ...
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1answer
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Atomic radius and nuclear effective charge in a group [closed]

Why even though the effective nuclear charge increases in gruop from top to bottom , the atomic radius increases too? Shouldn’t it decrease with more effective charge on valance electrons and ...
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1answer
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Niobium has a density of 8.57 g/cm3 and crystallizes with the body-centered cubic unit cell. Calculate the radius of a niobium atom

Here is my question Niobium has a density of $8.57 \pu{g/cm^3}$ and crystallizes with the body-centered cubic unit cell. Calculate the radius of a niobium atom. Here is my solution
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Calculate the atomic radius of iridium atom

I was delaying with this question as seen below. Calculate the radius of iridium atom, given that Ir has an FFC crystal structure, a density of $\pu{22.4 g/cm^3}$ and atomic weight of $\pu{192.2 ...
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Ar atomic radius Vs. Mg2+, Al3+ and F-

I find it difficult to understand why the Atomic radius of $\ce{Ar}$ is lower than the ionic radius of $\ce{Mg^2+}$ and $\ce{F-}$, and higher than $\ce{Al^3+}$. According to the tables I've seen: $$\...
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Na+ or Ca2+ . Which ion has the larger radius?

Which ion has the larger radius? Some sites say $r(\ce{Na+}) > r(\ce{Ca^2+})$. Any explanation would be appreciated.
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Which element has larger atomic radius — beryllium or xenon?

I say that xenon radius is smaller comparing to beryllium, but my friend says otherwise. What I think is that xenon is down in periodic table comparing to beryllium (3 periods down) and it's far ...
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1answer
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Acid-base chemistry - determining stability [closed]

I am learning about acid-base reactions and how to identify whether an acid is strong or not by looking at the conjugate base. The more stable a conjugate base the stronger the acid. However, two of ...
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1answer
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How to know which ionic compound have the highest lattice energy without knowing the values of the radii?

Given two ionic compounds, for instance: $$\ce{CaS} \quad \mathrm{or} \quad \ce{KCl}$$ What is the procedure to predict which of the two have the highest lattice energy (in absolute value)? (...
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Why can't we calculate the atomic radii of noble gases?

My book says that only the Van der Waal's radius of noble gases can be measured as these gases generally do not form compounds (except Xenon.) Then why can't we just calculate the atomic radii by ...
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Regular decrease in the atomic radius of 3d series

While comparing atomic radius, two factors are important: A. Decrease in size due to increase in effective nuclear charge B. Increase in size due to increase in shielding effect I was surprised to ...
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1answer
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Why is the distance between the atoms shorter in the dicarbon anion compared to the cation?

In general, the anions have bigger ionic radii than their corresponding neutral atoms, and the cations have smaller ionic radii then their corresponding neutral atoms. How come that does not apply to $...
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Ionic radius of Al[3+] compared to K[+], Ca[2+], S[2-], and Cl[-]

I came across this question: Which of the following is bigger? $$\ce{K+, Ca^2+, Al^3+, S^2-, Cl-}$$ Now, I know that the radius decreases as the period progresses to the right and increases ...
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Why the radius of noble gases is more than the halogens or the previous groups?

Noble gases have a larger radius than the halogens. Sometimes it is greater than the radius of group I elements. Why it is like that? When we talk about radius of noble gases what type of radius ...
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1answer
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What is the difference between the Bohr model and the quantum model?

Specifically, Bohrs atom model gives the radius of an atom as 0.53‎Å, while a quantum description offers a similar value. What is the difference between these?
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Predict the order of ionic radius

We have arrange the followig sequence for decreasing order of ionic radius . $Se^{-2},I^-,Br^{-},O^{-2},F^{-}$ In my book the answer given as $I^{-},Se^{-2},Br^{-},O^{-2},F^{-}$ But according to ...
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Newer ionic radii data than Shannon's 1976 compilation?

Shannon, R. D., 1976, Revised effective ionic radii and systematic studies of interatomic distances in halides and chalcogenides: Acta Crystallographica Section A, v. 32, p. 751–767. DOI: 10.1107/...
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How/where can I find a reliable atomic radii table?

I am currently working on a periodic table to include it in a experimental chemistry book and I would like to include non-bonded atomic radii data so it would be easier for the students to learn about ...
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Why does being “bonded” decrease atomic size?

I have a furiously overwhelming question- Why is the atomic size of noble gases larger than the atomic size of the previous halogen when atomic sizes decrease across a group? I did search it on ...
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Why isn't the ionic radius of Mg2+ bigger than F-? [closed]

They will both have the same number of valence electrons, but $\ce{F-}$ is more electronegative. Why is it not the case that $\ce{Mg^2+}$ has a bigger radius than $\ce{F-}$?
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Why the atomic (metallic) radius of gallium is less than that of aluminium?

It is a well known fact that on moving down the group of p-block elements, the atomic radius is expected to increase. However, gallium is an exception. The atomic radius i.e., the metallic radius of ...
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Bohr Radius Confusion

I saw online that the radius for each level is defined by the formula: $$r_n=n^2 r_1$$ Where $r_1$ is approximately $53\ \mathrm{pm}$. However, on the Barron's AP chemistry book 7th edition, it ...
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Why do atoms get smaller moving left to right on a periodic table? [duplicate]

I get that it's because of the increase number of protons, but I still don't understand the concept. When you move left to right on a periodic table, the protons increase at the same rate as the ...
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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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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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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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2answers
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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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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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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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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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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
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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 ...