What electronic geometry lacks a lone pair around the central atom and has bond angles of 180° or 120°?

The electronic geometry characterized by having no lone pairs around the central atom and exhibiting bond angles of 180° is linear. In a linear arrangement, two bonding pairs of electrons are positioned opposite each other. This configuration minimizes electron pair repulsion, thereby resulting in a bond angle of 180°.

In the case of trigonal planar, while it also lacks lone pairs, the presence of three bonds leads to bond angles of 120°, which differentiates it from the linear geometry. Octahedral geometry, typically featuring six bonds around a central atom, has bond angles of 90° and lacks lone pairs as well, but does not fit the described angles. Lastly, the tetrahedral structure involves four bonds that generate bond angles of approximately 109.5°, which again does not align with the options provided.

Thus, the linear electronic geometry is the correct answer, as it is specifically characterized by the absence of lone pairs and bond angles of 180°.