Trouble with picturing the 3-d structures

[tuha]

I know I am overthinking, as always, but for some reason I am just having so much trouble with picturing the 3-d structures (dash/wedge) when solving the problems. My test is tomorrow and I am stuck, I just can't draw them correctly...I get the hybridization, and the angle that will form.
What I don't get is how do you know where to draw a dash or a wedge, and when will the dash be to the upper left corner (extended) versus the lower left? Sometimes they are drawn near each other (dash and wedge going towards the upper left) with the one in the plane going towards the left. How do you determine this? Does it have to do with the bond angles? I tried figuring it out that way, but I still can't get the right figure without looking at the answer for a hint. For example: (CH3)3 N ... I have no idea how to orient my lewis dot to come up with the right three-d...how do you know which of the hydrogens will be off the plane and et.? Is there a simple way of doing this, and what is wrong with the way I am thinking?
Also, for a positive charged [H2COH] (+) molecule, why is the oxygen atom (as it says in my book) sp2? I know the carbon is sp2, but wouldn't trhe oxygen be sp3 because it's bonded to two things, and it also has 2 pairs of lone electrons?
Any help is greatly appreciated.

Thank you for your help in advance!

 

[ccl4]

To extend the ideas of valence-bond theory to polyatomic molecules, we must envision mixing s, p, and sometimes d orbitals to form hybrid orbitals. The process of hybridization leads to hybrid atomic orbitals that have a large lobe directed to overlap with orbitals on another atom to make a bond. Hybrid orbitals can also accommodate nonbonding pairs. A particular mode of hybridization can be associated with each of the five common electron-domain geometries ( trigonal trigonal and ).

Covalent bonds in which the electron density lies along the line connecting the atoms (the internuclear axis) are called sigma bonds. Bonds can also be formed from the sideways overlap of p orbitals. Such a bond is called a pi bond. A double bond, such as that in consists of one bond and one bond; a triple bond, such as that in consists of one and two bonds. The formation of a bond requires that molecules adopt a specific orientation; the two groups in for example, must lie in the same plane. As a result, the presence of bonds introduces rigidity into molecules. In molecules that have multiple bonds and more than one resonance structure, such as the bonds are delocalized; that is, the bonds are spread among several atoms.

 

[Blueshift5]

I understand that visualizing three-dimensional structures can be challenging. It is important to remember that these structures are representations of molecules and are not always exact depictions. Additionally, there is no one right way to draw a molecule's structure, as long as the correct bonding and hybridization is shown.

To answer your question about the dash and wedge representation, these symbols indicate the orientation of the bonds in a three-dimensional space. The dash represents a bond that is going into the plane of the paper, while the wedge represents a bond that is coming out of the plane. The placement of these symbols is determined by the relative positions of the atoms in the molecule. For example, in (CH3)3N, the three methyl groups are all in different planes, so the dashes and wedges will be drawn accordingly to show this.

In terms of determining the orientation of the bonds, it is helpful to visualize the molecule in three dimensions and consider the bond angles. For example, in a tetrahedral molecule like (CH3)3N, the bond angles are all approximately 109.5 degrees, so the bonds will be drawn accordingly.

As for your question about the positive charged molecule [H2COH] (+), the oxygen atom is indeed sp2 hybridized. This is because the oxygen atom has three regions of electron density (two bonds and one lone pair), which results in a trigonal planar geometry and sp2 hybridization. The carbon atom is also sp2 hybridized in this molecule.

I hope this helps to clarify your understanding of three-dimensional structures and their representation. Remember that practice and visualizing molecules in 3D can greatly improve your ability to draw accurate structures. Good luck on your test tomorrow!