Draw the Lewis structure of ethyne (C₂H₂) and then choose the appropriate pair of molecular geometries of the two central atoms. Your answer choice is independent of the orientation of your drawn structure. A) linear / linear
B) trigonal/pyramidal
C) pyramidal/trigonal
D) trigonal pyramidal/trigonal pyramidal
E) planar / linear

A) linear / linear

Explanation:

In this case, we have a triple bond beetween the atoms (See figure 1). If we have this triple bond we will have an Sp hybridization (in both carbons). We have to remember the relationship between the geometry and the hybridization:

-) Sp3 = Tetrahedral

-) Sp2 = Trigonal

-) Sp = Linear

Due to the hybridization, we will have a linear structure between the atoms. The angle between the atoms is 180º (See figure 2).

So, if we have a hybridization Sp for both carbons, we will have a linear geometry in each carbon. Therefore, the answer is A.