But as soon as this attack takes place, we form a tetrahedral intermediate. And on top of that we're going to have a negative charge on this oxygen and this tetrahedral intermediate. Because of that negative charge, and because this molecule is no longer planar, it's not going to be a stable. So in step one, we formed a relatively unstable tetrahedral intermediate. So we call it a tetrahedral because here we have one, two, three sigma bonds. And here the carbon has 1234 sigma bonds.