[physicsdude69]

how would you draw this structure in 3d using dash-wedge representation?

HN=C=CH2

From my guess, I drew the N=C=C as being parallel, and the two hydrogens coming off the second C without having any dashes or wedges, but curving at 120 degrees from the carbon. For the HN, I had the H represented using a dark wedged line. To represent the N I had a dashed line going out, with 2 electrons depicted at the end of that dashed line to represents Nitrogens 2 free electrons.

Is this accurate and if not what is the right way? And what is the hybridization of the N in HN=C=CH2?

[nj_bartel]

The nitrogen is sp² hybridized.  I want to say the whole molecule would lie in one plane, with the hydrogens/lp in 120^o bond angles.  I'm not positive that the geometry would be 180^o for a =C= bond though.

[physicsdude69]

The nitrogen is sp² hybridized.  I want to say the whole molecule would lie in one plane, with the hydrogens/lp in 120^o bond angles.  I'm not positive that the geometry would be 180^o for a =C= bond though.

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but carbon is sp hybridized, and dont sp hybridized atoms have an angle of 180? and where would the dashes and wedges go? would a wedge be drawn from nitrogen to the electron pair of that nitrogen?

[nj_bartel]

Ok, yea, sp hybridization would make sense for a =C=.  There don't necessarily have to be wedges/dashes in a structure, take for example ethylene that lies in the plane of the paper.

[AWK]

Look at allene
http://en.wikipedia.org/wiki/Allene

change one C for N and remove one hydrogen atom from that atom