How many nodes are in the highest energy molecular orbital of benzene?

I have read that PH5 does not exist and was wondering why.  Why can't the s orbitals from hydrogen form a bond with the five sp3d hybrid orbital from phosphorus?  I've also read that PH4 does exist.  Wouldn't the s orbitals on hydrogen form a bond with the sp3d hybrid orbitals there also with a free electron?

In cyclooctatetrane, how many electrons are in nonbonding molecular orbitals?

Molecular orbitals are formed from linear combinations of atomic orbitals. Which of the following hybridizations could be involved in the complete molecular orbital configuration of homonuclear diatomic species?

H-He-H2+ is a linear trinuclear with He occupying the central position and the two hydrogen occupying the terminal positions. Build a reasonable qualitative molecular orbital diagram

Draw the molecular orbital diagram for HCI. Clearly label the axes, MO's, atomic orbitals. Show the distibution of the electrons in the MO's. Roughly sketch the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO). Answer the next two questions based on your HCI MO diagram. Based on your MO diagram, what would be the bond order of HCI+2 jon? In the molecular orbital diagram of HCI, there are two non-bonding molecular orbitals with a total of 4 electrons occupying them. O True O False

4) a) Draw the p-orbitals that are involved in the pi-system in molecule 1 shown below. Make sure to include shading and put any lone pairs that are in a p-orbital in one in your drawing. H₂N Carbon 3 Carbon 2 1 H3CO Carbon 1 b) Are the p-orbitals on carbon 1 and carbon 2 in molecule 1 in conjugation with each other? (ie are the p- orbitals pointing in the same direction). Explain your reasoning.

2) a) Consider the following molecule . Given what you have learned about hybridization theory, draw an image or images explaining the bonding situation in this molecule. I want you to draw out all of the orbitals, hybrid orbitals and how they overlap to form the bonds in the molecule. Indicate the % s or p character in the given atomic and hybrid orbitals. Which C-C bond or bonds are the longest? In a paragraph or so explain the image or images you just drew. b) Lastly, consider the molecule below. Indicate the Molecular formula, the molar mass, label the hybridization of each atom except for hydrogen, indicate any chiral centers with a *, which bond or bonds are the shortest, identify by name of each functional group with an arrow pointing to the group.

The molecule below has 10 o bonds. For Parts 1-4, determine the number of specified orbitals. H,C- -CH3