Linear
Chemical Structure
The linear geometry is characterized by two atoms bonded to a central atom.
Let's focus on beryllium, Be, as the central atom as discussed in Section 8.5
of the textbook.
What group and row do you find Be in the Periodic Table?
In the linear molecular structure for Be, there are no lone electron pairs
(non-bonding electron pairs) on the central atom.
There are only two electron pairs around the central atom and they are all bonding electrons.
The molecule is perfectly happy in this state, and it is an exception
to the octet rule that we learned, or will soon learn, in class.
The molecule has both a linear molecular geometry and a linear electronic geometry.
Take a look at the overall geometry below. The central atom is in white,
the two other atoms are in red, and the bonds are shown in blue.
Place the cursor over the molecule, press and hold the left button down, and move the mouse.
You should be able to spin the molecule in any direction, and examine the orientation of
the atoms. (If the image looks weird, like it is only partially shown or it looks like a double image,
click the refresh button of your browser. It is at the top in the toolbar.)
The white atom represents Be. The two atoms shown in red are most commonly one of the halides. The halides are
in Group VIIA of the Periodic Table. Convince yourself that all three atoms lie in a single geometric line.
This is where the name "linear" arises.
Name chemical formulas for three molecules with Be as the central atom
that are expected to have the linear chemical structure?
Orbitals
In the linear molecular structure, the two chemical bonds are sp hybrid orbitals on the central white atom.
How many s orbitals and how many p orbitals on the central atom are used to create the two sp orbitals?
Convince yourself that there are two p orbitals on the central atom that do not
participate in forming the sp orbitals.
Below is the same chemical structure as shown above, except the unhybridized p orbitals are also shown.
Rotate the structure with your mouse.
How would you describe the orientation of the unhybridized p orbitals relative to the geometric line
in which all three atoms lie?
Are the unhybridized p orbitals occupied or unoccupied by electrons?
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