Water depletion results in a rather noticeable structure rearrangement.
Crystal structure of $\ce{Ca2B6O11}$ [1] is actually deposited in ICSD database (#23032).
Unit cell: $8.68(1)$, $8.56(1)$, $10.78(2)$, $90.00$, $90.00$, $110.0(1)$; space group $P1\,1\, 21/b$ monoclinic, $Z = 4$:
For clarity coordination polyhedra are only shown for $\ce{[BO4]}$.
Cross-linked structure features trimeric linear assemblies of $\ce{[BO4]}$ units connected via vertices into the 3D motif with $\ce{Ca}$ and $\ce{[BO3]}$. In order to answer your question regarding atom bonding, here are the environmental listings for all crystallographically non-equivalent atoms. for the quick reference, maximum number of nearest neighbous of oxygen is $4$, e.g. for $\mathrm{O2}$:
Boron
Forms two types of coordination polyhedra with oxygen: planar trigonal (C.N. = 3) and tetrahedral (C.N. = 4).
Water depletion results in a rather noticeable structure rearrangement.
Crystal structure of $\ce{Ca2B6O11}$ [1] is actually deposited in ICSD database (#23032). Unit cell: $8.68(1)$, $8.56(1)$, $10.78(2)$, $90.00$, $90.00$, $110.0(1)$; space group $P1\,1\, 21/b$ monoclinic, $Z = 4$:
For clarity coordination polyhedra are only shown for $\ce{[BO4]}$.
Cross-linked structure features trimeric linear assemblies of $\ce{[BO4]}$ units connected via vertices into the 3D motif with $\ce{Ca}$ and $\ce{[BO3]}$. In order to answer your question regarding atom bonding, here are the environmental listings for all crystallographically non-equivalent atoms. for the quick reference, maximum number of nearest neighbous of oxygen is $4$, e.g. for $\mathrm{O2}$:
Boron
Forms two types of coordination polyhedra with oxygen: planar trigonal (C.N. = 3) and tetrahedral (C.N. = 4).
1) Oxygen CAN form 3 or 4 bonds. The most common example is $\ce{H3O+}$ ion This form of bonding is critical to understand basic nature of ammonia solutions, so for exact description of it look that part of the book.
2)Boron also can form more than 3 bonds if at least one its partner provides an electron pair for bonding, not one electron.
As a general rule I prefer to stay away from the chemistry of borates and alumina-silicates as it is ruled largely by ionic interactions and non-intuitive hydration/dehydration.
===========
In structural diagrams of polymeric salts 'unit' often refers to some recurring fragment... however, it is not nessesarily has same stochiometry than formal anion. In alumosilicates the anionic frame consists of $\ce{AlO4-}$ and $\ce{SiO4}$ tetrahedral units. However, they are usually connected by shared vertexes, so the exact formula of formal anion is different. Borates are a bit more complex system, since they may include both $\ce{BO3}$ and $\ce{BO4-}$ units, and oxygen is often connected to hydrogen.
==========
I looked into open cristallographic database. Unsurprisingly, it does NOT feature a compound $\ce{Ca2B6O11}$. However, salts are often written in 'dehydrated' form, so I looked for any borate with $\ce{Ca:B} = 1:3$ stochiometry. Several with rather complex crystal structure were found, so I left only two: one with rather simple structure of typical 'hidrated' borate anion and one with rather complex continous 'dehydrated' boron-oxygen layers. Note: the structures are refined from X-Ray , so they does not reveal hydrogen positions. Isolated oxygens of water molecules and cations are omitted.
$\ce{B3O8}$ unit from mineral Inyoite, $\ce{CaB3O3(OH)5·4(H2O)}$
$\ce{[B3O6]_{\infty}}$ layer from mineral Fabianite $\ce{CaB3O5(OH)}$
1) Oxygen CAN form 3 or 4 bonds. The most common example is $\ce{H3O+}$ ion This form of bonding is critical to understand basic nature of ammonia solutions, so for exact description of it look that part of the book.
2)Boron also can form more than 3 bonds if at least one its partner provides an electron pair for bonding, not one electron.
As a general rule I prefer to stay away from the chemistry of borates and alumina-silicates as it is ruled largely by ionic interactions and non-intuitive hydration/dehydration.
===========
In structural diagrams of polymeric salts 'unit' often refers to some recurring fragment... however, it is not nessesarily has same stochiometry than formal anion. In alumosilicates the anionic frame consists of $\ce{AlO4-}$ and $\ce{SiO4}$ tetrahedral units. However, they are usually connected by shared vertexes, so the exact formula of formal anion is different. Borates are a bit more complex system, since they may include both $\ce{BO3}$ and $\ce{BO4-}$ units, and oxygen is often connected to hydrogen.
==========
I looked into open cristallographic database. Unsurprisingly, it does NOT feature a compound $\ce{Ca2B6O11}$. However, salts are often written in 'dehydrated' form, so I looked for any borate with $\ce{Ca:B} = 1:3$ stochiometry. Several with rather complex crystal structure were found, so I left only two: one with rather simple structure of typical 'hidrated' borate anion and one with rather complex continous 'dehydrated' boron-oxygen layers. Note: the structures are refined from X-Ray , so they does not reveal hydrogen positions. Isolated oxygens of water molecules and cations are omitted.
$\ce{B3O8}$ unit from mineral Inyoite, $\ce{CaB3O3(OH)5·4(H2O)}$
$\ce{[B3O6]_{\infty}}$ layer from mineral Fabianite $\ce{CaB3O5(OH)}$
The crystal structure of $\ce{Ca2B6O11}$ has actually been deposited to Inorganic Crystal Structure Database in 1980 and modified in 1987. The reference number is #23032.More
You will have better idea if you see 2D structure instead of 3D
You can clearly see no $\ce{O}$ atom have more then 3 bonds!
You will have better idea if you see 2D structure instead of 3D
You can clearly see no $\ce{O}$ atom have more then 3 bonds!
More
VOTE
$\ce{Ca2B6O11}$ is an anhydrous form of several main boron minerals with well-established both compositions and structures, such as:
Water depletion results in a rather noticeable structure rearrangement.
Crystal structure of $\ce{Ca2B6O11}$ [1] is actually deposited in ICSD database (#23032).
Unit cell: $8.68(1)$, $8.56(1)$, $10.78(2)$, $90.00$, $90.00$, $110.0(1)$; space group $P1\,1\, 21/b$ monoclinic, $Z = 4$:
$\color{#804000}{\Large\bullet}~\ce{B}$; $\color{#FF0D0D}{\Large\bullet}~\ce{O}$; $\color{#3DFF00}{\Large\bullet}~\ce{Ca}$.
For clarity coordination polyhedra are only shown for $\ce{[BO4]}$.
Cross-linked structure features trimeric linear assemblies of $\ce{[BO4]}$ units connected via vertices into the 3D motif with $\ce{Ca}$ and $\ce{[BO3]}$. In order to answer your question regarding atom bonding, here are the environmental listings for all crystallographically non-equivalent atoms. for the quick reference, maximum number of nearest neighbous of oxygen is $4$, e.g. for $\mathrm{O2}$:
Boron
Forms two types of coordination polyhedra with oxygen: planar trigonal (C.N. = 3) and tetrahedral (C.N. = 4).
Oxygen
Calcium
Features two heavily distorted oxo-environments with C.N. = 6 and C.N. = 8.
Bibliography
$\ce{Ca2B6O11}$ is an anhydrous form of several main boron minerals with well-established both compositions and structures, such as:
Water depletion results in a rather noticeable structure rearrangement.
Crystal structure of $\ce{Ca2B6O11}$ [1] is actually deposited in ICSD database (#23032).
Unit cell: $8.68(1)$, $8.56(1)$, $10.78(2)$, $90.00$, $90.00$, $110.0(1)$; space group $P1\,1\, 21/b$ monoclinic, $Z = 4$:
$\color{#804000}{\Large\bullet}~\ce{B}$;$\color{#FF0D0D}{\Large\bullet}~\ce{O}$;$\color{#3DFF00}{\Large\bullet}~\ce{Ca}$.
For clarity coordination polyhedra are only shown for $\ce{[BO4]}$.
Cross-linked structure features trimeric linear assemblies of $\ce{[BO4]}$ units connected via vertices into the 3D motif with $\ce{Ca}$ and $\ce{[BO3]}$. In order to answer your question regarding atom bonding, here are the environmental listings for all crystallographically non-equivalent atoms. for the quick reference, maximum number of nearest neighbous of oxygen is $4$, e.g. for $\mathrm{O2}$:
Boron
Forms two types of coordination polyhedra with oxygen: planar trigonal (C.N. = 3) and tetrahedral (C.N. = 4).
Oxygen
Calcium
Features two heavily distorted oxo-environments with C.N. = 6 and C.N. = 8.
Bibliography
More
VOTE
1) Oxygen CAN form 3 or 4 bonds. The most common example is $\ce{H3O+}$ ion This form of bonding is critical to understand basic nature of ammonia solutions, so for exact description of it look that part of the book.
2)Boron also can form more than 3 bonds if at least one its partner provides an electron pair for bonding, not one electron.
As a general rule I prefer to stay away from the chemistry of borates and alumina-silicates as it is ruled largely by ionic interactions and non-intuitive hydration/dehydration.
===========
In structural diagrams of polymeric salts 'unit' often refers to some recurring fragment... however, it is not nessesarily has same stochiometry than formal anion. In alumosilicates the anionic frame consists of $\ce{AlO4-}$ and $\ce{SiO4}$ tetrahedral units. However, they are usually connected by shared vertexes, so the exact formula of formal anion is different. Borates are a bit more complex system, since they may include both $\ce{BO3}$ and $\ce{BO4-}$ units, and oxygen is often connected to hydrogen.
==========
I looked into open cristallographic database. Unsurprisingly, it does NOT feature a compound $\ce{Ca2B6O11}$. However, salts are often written in 'dehydrated' form, so I looked for any borate with $\ce{Ca:B} = 1:3$ stochiometry. Several with rather complex crystal structure were found, so I left only two: one with rather simple structure of typical 'hidrated' borate anion and one with rather complex continous 'dehydrated' boron-oxygen layers. Note: the structures are refined from X-Ray , so they does not reveal hydrogen positions. Isolated oxygens of water molecules and cations are omitted.
$\ce{B3O8}$ unit from mineral Inyoite, $\ce{CaB3O3(OH)5·4(H2O)}$
$\ce{[B3O6]_{\infty}}$ layer from mineral Fabianite $\ce{CaB3O5(OH)}$
and its main building block
1) Oxygen CAN form 3 or 4 bonds. The most common example is $\ce{H3O+}$ ion This form of bonding is critical to understand basic nature of ammonia solutions, so for exact description of it look that part of the book.
2)Boron also can form more than 3 bonds if at least one its partner provides an electron pair for bonding, not one electron.
As a general rule I prefer to stay away from the chemistry of borates and alumina-silicates as it is ruled largely by ionic interactions and non-intuitive hydration/dehydration.
===========
In structural diagrams of polymeric salts 'unit' often refers to some recurring fragment... however, it is not nessesarily has same stochiometry than formal anion. In alumosilicates the anionic frame consists of $\ce{AlO4-}$ and $\ce{SiO4}$ tetrahedral units. However, they are usually connected by shared vertexes, so the exact formula of formal anion is different. Borates are a bit more complex system, since they may include both $\ce{BO3}$ and $\ce{BO4-}$ units, and oxygen is often connected to hydrogen.
==========
I looked into open cristallographic database. Unsurprisingly, it does NOT feature a compound $\ce{Ca2B6O11}$. However, salts are often written in 'dehydrated' form, so I looked for any borate with $\ce{Ca:B} = 1:3$ stochiometry. Several with rather complex crystal structure were found, so I left only two: one with rather simple structure of typical 'hidrated' borate anion and one with rather complex continous 'dehydrated' boron-oxygen layers. Note: the structures are refined from X-Ray , so they does not reveal hydrogen positions. Isolated oxygens of water molecules and cations are omitted.
$\ce{B3O8}$ unit from mineral Inyoite, $\ce{CaB3O3(OH)5·4(H2O)}$
$\ce{[B3O6]_{\infty}}$ layer from mineral Fabianite $\ce{CaB3O5(OH)}$
and its main building block
More
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