Why does the beryllium 2+ ion have a larger radius than a helium atom?
$begingroup$
$ce{Be^2+}$ has an ionic radius of $pu{45 pm}$, while $ce{He}$ has a radius of only $pu{31 pm}$. If they have the same number of electrons (two, in the $mathrm{1p}$ orbital), and $ce{Be}$ has more protons to attract them, why doesn't $ce{Be^2+}$ have a smaller radius?
atomic-radius
edited 19 hours ago
andselisk
16.4k653115
asked 20 hours ago
TrumpetDudeTrumpetDude
415
$endgroup$
add a comment |
$begingroup$
$ce{Be^2+}$ has an ionic radius of $pu{45 pm}$, while $ce{He}$ has a radius of only $pu{31 pm}$. If they have the same number of electrons (two, in the $mathrm{1p}$ orbital), and $ce{Be}$ has more protons to attract them, why doesn't $ce{Be^2+}$ have a smaller radius?
atomic-radius
edited 19 hours ago
andselisk
16.4k653115
asked 20 hours ago
TrumpetDudeTrumpetDude
415
$endgroup$
2
$begingroup$
He has VDW radisum of 140 pm, what particular radius of He are your referring to? There is more than one.
$endgroup$
– permeakra
20 hours ago
2
$begingroup$
It's probably down to different definitions and/or measuring techniques.
$endgroup$
– TAR86
19 hours ago
add a comment |
$begingroup$
$ce{Be^2+}$ has an ionic radius of $pu{45 pm}$, while $ce{He}$ has a radius of only $pu{31 pm}$. If they have the same number of electrons (two, in the $mathrm{1p}$ orbital), and $ce{Be}$ has more protons to attract them, why doesn't $ce{Be^2+}$ have a smaller radius?
atomic-radius
edited 19 hours ago
andselisk
16.4k653115
asked 20 hours ago
TrumpetDudeTrumpetDude
415
$endgroup$
$ce{Be^2+}$ has an ionic radius of $pu{45 pm}$, while $ce{He}$ has a radius of only $pu{31 pm}$. If they have the same number of electrons (two, in the $mathrm{1p}$ orbital), and $ce{Be}$ has more protons to attract them, why doesn't $ce{Be^2+}$ have a smaller radius?
atomic-radius
atomic-radius
edited 19 hours ago
andselisk
16.4k653115
asked 20 hours ago
TrumpetDudeTrumpetDude
415
edited 19 hours ago
andselisk
16.4k653115
asked 20 hours ago
TrumpetDudeTrumpetDude
415
edited 19 hours ago
andselisk
16.4k653115
edited 19 hours ago
andselisk
16.4k653115
edited 19 hours ago
andselisk
16.4k653115
16.4k653115
asked 20 hours ago
TrumpetDudeTrumpetDude
415
asked 20 hours ago
TrumpetDudeTrumpetDude
415
asked 20 hours ago
TrumpetDudeTrumpetDude
415
415
2
$begingroup$
He has VDW radisum of 140 pm, what particular radius of He are your referring to? There is more than one.
$endgroup$
– permeakra
20 hours ago
2
$begingroup$
It's probably down to different definitions and/or measuring techniques.
$endgroup$
– TAR86
19 hours ago
add a comment |
2
$begingroup$
He has VDW radisum of 140 pm, what particular radius of He are your referring to? There is more than one.
$endgroup$
– permeakra
20 hours ago
2
$begingroup$
It's probably down to different definitions and/or measuring techniques.
$endgroup$
– TAR86
19 hours ago
2
2
$begingroup$
He has VDW radisum of 140 pm, what particular radius of He are your referring to? There is more than one.
$endgroup$
– permeakra
20 hours ago
$begingroup$
He has VDW radisum of 140 pm, what particular radius of He are your referring to? There is more than one.
$endgroup$
– permeakra
20 hours ago
2
2
$begingroup$
It's probably down to different definitions and/or measuring techniques.
$endgroup$
– TAR86
19 hours ago
$begingroup$
It's probably down to different definitions and/or measuring techniques.
$endgroup$
– TAR86
19 hours ago
add a comment |
1 Answer
1
active
oldest
votes
$begingroup$
You are mixing apples and oranges.
Or, to be more precise, an ionic radius for $ce{Be^2+}$ with coordination number (C.N.) 6 and van der Waals radius of $ce{He}$.
To make it clear I compiled data for van der Waals and covalent radii [1, p. 9-58] as well as ionic radii [1, p. 12-13]:
$$
begin{array}{lccccc}
hline
text{Element} & R_mathrm{vdW}/pu{Å} & R_mathrm{cov}/pu{Å} & text{Ion} & text{C.N.} & R_mathrm{i}/pu{Å} \
hline
ce{Be} & 1.52 & 0.99 & ce{Be^2+} & 4 & 0.27 \
& & & & 6 & 0.45 \
ce{He} & 1.40 & 0.37 & & & \
hline
end{array}
$$
Apparently, there is no experimental ionic radii for helium to compare with as helium, well, represents one of the most non-reactive elements.
Also, all radii set are determined using various methods and cannot be directly compared.
From the foreword [1. p. 9-58]:
There are many scales of van der Waals radii, but they are not fully consistent with one another. The van der Waals radii determined by Bondi [...] from x-ray diffraction data, crystal densities, gas kinetic collision cross sections, critical densities, and liquid-
state properties are the most widely used values. [...]
The covalent radii tabulated here are recommendations for single covalent bonds,
and they are based on a comprehensive evaluation of experimental data [...].
Ionic radii are estimated first and foremost from the experimental crystal structure data, averaged and supplemented by empirical and theoretical calculations (extrapolations, e.g. using Zachariasen method).
References
- Haynes, W. M.; Lide, D. R.; Bruno, T. J. CRC Handbook of Chemistry and Physics: A Ready-Reference Book of Chemical and Physical Data.; 2017; Vol. 97. ISBN 978-1-4987-5429-3.
answered 19 hours ago
andseliskandselisk
16.4k653115
$endgroup$
add a comment |
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1 Answer
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$begingroup$
You are mixing apples and oranges.
Or, to be more precise, an ionic radius for $ce{Be^2+}$ with coordination number (C.N.) 6 and van der Waals radius of $ce{He}$.
To make it clear I compiled data for van der Waals and covalent radii [1, p. 9-58] as well as ionic radii [1, p. 12-13]:
$$
begin{array}{lccccc}
hline
text{Element} & R_mathrm{vdW}/pu{Å} & R_mathrm{cov}/pu{Å} & text{Ion} & text{C.N.} & R_mathrm{i}/pu{Å} \
hline
ce{Be} & 1.52 & 0.99 & ce{Be^2+} & 4 & 0.27 \
& & & & 6 & 0.45 \
ce{He} & 1.40 & 0.37 & & & \
hline
end{array}
$$
Apparently, there is no experimental ionic radii for helium to compare with as helium, well, represents one of the most non-reactive elements.
Also, all radii set are determined using various methods and cannot be directly compared.
From the foreword [1. p. 9-58]:
There are many scales of van der Waals radii, but they are not fully consistent with one another. The van der Waals radii determined by Bondi [...] from x-ray diffraction data, crystal densities, gas kinetic collision cross sections, critical densities, and liquid-
state properties are the most widely used values. [...]
The covalent radii tabulated here are recommendations for single covalent bonds,
and they are based on a comprehensive evaluation of experimental data [...].
Ionic radii are estimated first and foremost from the experimental crystal structure data, averaged and supplemented by empirical and theoretical calculations (extrapolations, e.g. using Zachariasen method).
References
- Haynes, W. M.; Lide, D. R.; Bruno, T. J. CRC Handbook of Chemistry and Physics: A Ready-Reference Book of Chemical and Physical Data.; 2017; Vol. 97. ISBN 978-1-4987-5429-3.
answered 19 hours ago
andseliskandselisk
16.4k653115
$endgroup$
add a comment |
$begingroup$
You are mixing apples and oranges.
Or, to be more precise, an ionic radius for $ce{Be^2+}$ with coordination number (C.N.) 6 and van der Waals radius of $ce{He}$.
To make it clear I compiled data for van der Waals and covalent radii [1, p. 9-58] as well as ionic radii [1, p. 12-13]:
$$
begin{array}{lccccc}
hline
text{Element} & R_mathrm{vdW}/pu{Å} & R_mathrm{cov}/pu{Å} & text{Ion} & text{C.N.} & R_mathrm{i}/pu{Å} \
hline
ce{Be} & 1.52 & 0.99 & ce{Be^2+} & 4 & 0.27 \
& & & & 6 & 0.45 \
ce{He} & 1.40 & 0.37 & & & \
hline
end{array}
$$
Apparently, there is no experimental ionic radii for helium to compare with as helium, well, represents one of the most non-reactive elements.
Also, all radii set are determined using various methods and cannot be directly compared.
From the foreword [1. p. 9-58]:
There are many scales of van der Waals radii, but they are not fully consistent with one another. The van der Waals radii determined by Bondi [...] from x-ray diffraction data, crystal densities, gas kinetic collision cross sections, critical densities, and liquid-
state properties are the most widely used values. [...]
The covalent radii tabulated here are recommendations for single covalent bonds,
and they are based on a comprehensive evaluation of experimental data [...].
Ionic radii are estimated first and foremost from the experimental crystal structure data, averaged and supplemented by empirical and theoretical calculations (extrapolations, e.g. using Zachariasen method).
References
- Haynes, W. M.; Lide, D. R.; Bruno, T. J. CRC Handbook of Chemistry and Physics: A Ready-Reference Book of Chemical and Physical Data.; 2017; Vol. 97. ISBN 978-1-4987-5429-3.
answered 19 hours ago
andseliskandselisk
16.4k653115
$endgroup$
add a comment |
$begingroup$
You are mixing apples and oranges.
Or, to be more precise, an ionic radius for $ce{Be^2+}$ with coordination number (C.N.) 6 and van der Waals radius of $ce{He}$.
To make it clear I compiled data for van der Waals and covalent radii [1, p. 9-58] as well as ionic radii [1, p. 12-13]:
$$
begin{array}{lccccc}
hline
text{Element} & R_mathrm{vdW}/pu{Å} & R_mathrm{cov}/pu{Å} & text{Ion} & text{C.N.} & R_mathrm{i}/pu{Å} \
hline
ce{Be} & 1.52 & 0.99 & ce{Be^2+} & 4 & 0.27 \
& & & & 6 & 0.45 \
ce{He} & 1.40 & 0.37 & & & \
hline
end{array}
$$
Apparently, there is no experimental ionic radii for helium to compare with as helium, well, represents one of the most non-reactive elements.
Also, all radii set are determined using various methods and cannot be directly compared.
From the foreword [1. p. 9-58]:
There are many scales of van der Waals radii, but they are not fully consistent with one another. The van der Waals radii determined by Bondi [...] from x-ray diffraction data, crystal densities, gas kinetic collision cross sections, critical densities, and liquid-
state properties are the most widely used values. [...]
The covalent radii tabulated here are recommendations for single covalent bonds,
and they are based on a comprehensive evaluation of experimental data [...].
Ionic radii are estimated first and foremost from the experimental crystal structure data, averaged and supplemented by empirical and theoretical calculations (extrapolations, e.g. using Zachariasen method).
References
- Haynes, W. M.; Lide, D. R.; Bruno, T. J. CRC Handbook of Chemistry and Physics: A Ready-Reference Book of Chemical and Physical Data.; 2017; Vol. 97. ISBN 978-1-4987-5429-3.
answered 19 hours ago
andseliskandselisk
16.4k653115
$endgroup$
You are mixing apples and oranges.
Or, to be more precise, an ionic radius for $ce{Be^2+}$ with coordination number (C.N.) 6 and van der Waals radius of $ce{He}$.
To make it clear I compiled data for van der Waals and covalent radii [1, p. 9-58] as well as ionic radii [1, p. 12-13]:
$$
begin{array}{lccccc}
hline
text{Element} & R_mathrm{vdW}/pu{Å} & R_mathrm{cov}/pu{Å} & text{Ion} & text{C.N.} & R_mathrm{i}/pu{Å} \
hline
ce{Be} & 1.52 & 0.99 & ce{Be^2+} & 4 & 0.27 \
& & & & 6 & 0.45 \
ce{He} & 1.40 & 0.37 & & & \
hline
end{array}
$$
Apparently, there is no experimental ionic radii for helium to compare with as helium, well, represents one of the most non-reactive elements.
Also, all radii set are determined using various methods and cannot be directly compared.
From the foreword [1. p. 9-58]:
There are many scales of van der Waals radii, but they are not fully consistent with one another. The van der Waals radii determined by Bondi [...] from x-ray diffraction data, crystal densities, gas kinetic collision cross sections, critical densities, and liquid-
state properties are the most widely used values. [...]
The covalent radii tabulated here are recommendations for single covalent bonds,
and they are based on a comprehensive evaluation of experimental data [...].
Ionic radii are estimated first and foremost from the experimental crystal structure data, averaged and supplemented by empirical and theoretical calculations (extrapolations, e.g. using Zachariasen method).
References
- Haynes, W. M.; Lide, D. R.; Bruno, T. J. CRC Handbook of Chemistry and Physics: A Ready-Reference Book of Chemical and Physical Data.; 2017; Vol. 97. ISBN 978-1-4987-5429-3.
answered 19 hours ago
andseliskandselisk
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edited 14 hours ago
answered 19 hours ago
andseliskandselisk
16.4k653115
answered 19 hours ago
andseliskandselisk
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answered 19 hours ago
andseliskandselisk
16.4k653115
16.4k653115
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$begingroup$
He has VDW radisum of 140 pm, what particular radius of He are your referring to? There is more than one.
$endgroup$
– permeakra
20 hours ago
2
$begingroup$
It's probably down to different definitions and/or measuring techniques.
$endgroup$
– TAR86
19 hours ago