← All study tools

Wedge & Dash Lab

A page is flat, but most molecules are not. Wedges and dashes show which atoms stick out of the page. Turn the model, watch the drawing change, then practise until it is automatic.

Plain lineThe bond lies in the page.
Solid wedgeThe atom comes out of the page, toward you. It looks bigger because it is closer.
Hashed wedge (dash)The atom goes behind the page, away from you.

The thin end of a wedge always starts at the central atom. The wide end is at the atom that sticks out.

Pick a molecule

1 · The real molecule (drag to turn it)

2 · What you draw from this view

3 · Seen from above

When do I need wedges and dashes?
  1. Flat shapes need none. Linear, trigonal planar and bent molecules have all their atoms in one plane, so the whole molecule lies in the page: plain lines only.
  2. Tetrahedral: a page can hold the central atom and only 2 of the 4 outer atoms. Draw those 2 as plain lines in a V. Of the other two, one is in front (wedge) and one is behind (dash).
  3. Trigonal pyramidal: draw the lone pair on top, then 1 plain line, 1 wedge and 1 dash below it.
  4. Always draw the central atom's lone pairs. They are why the shape is what it is.