Hybrization of H in HNO There is a problem that states: Find the molecular geometry of each molecule and the hybridization of each atom in the molecule. The two molecules are HNO and HCN. I found HNO to be sp3 hybridized and HCN to be sp hybridized. However, it says that only N and O are hybridized in the first. While all three are hybridized in the second. Why is hydrogen listed as sp hybridized?
Hybridization refers to the orbitals that each atom is using to make bonds.  In $\ce{HNO}$, the $\ce{N}$ and $\ce{O}$ are $sp^2$ hybridized.  This means they form a sigma bond with an $sp^2$ orbital from each and the pi bond from the interaction of the non-hybridized $p$ orbital on each.  The $\ce{N}$ also has a $sp^2$ orbital overlap with the $1s$ of $\ce{H}$, which forms a sigma bond.  Each of the lone pairs on the $\ce{N}$ and $\ce{O}$ is in an $sp^2$ orbital.

In $\ce{HCN}$ the carbon is $sp$ hybridized, as is the $\ce{N}$.  $\ce{C}$ and $\ce{N}$ form a sigma bond with $sp$ overlap, and the pi bond from the interaction of both of their non-hybridized $p$ orbitals (to form a triple bond).  The lone pair of $\ce{N}$ is in an $sp$ orbital, and the $\ce{C-H}$ bond is from an $sp$ overlap with the $1s$ of $\ce{H}$.

None of these molecules have $sp^3$ hybridization.