# Ammonia sigma bonds p character

Why does ammonia's sigma bonds to H have more p character than let's say ethane.

I am guessing it has something to do with the effect the lone pair has on bond lengths and angles, but not quite sure what the effect is exactly.

You'd rather have a higher $s$ character for the lone pair orbital. An ordinary bonding pair is already stabilized between two nuclei, so stabilizing the lone pair can help to further stabilize the system. Putting higher $s$ character into the lone pair orbital makes the orbital smaller and pulls the electrons closer to the nucleus.
This leaves more $p$ character in the other orbitals.