(a) How does the structure of diborane $\left(\mathrm{B}_{2} \mathrm{H}_{6}\right)\( differ from that of ethane \)\left(\mathrm{C}_{2} \mathrm{H}_{6}\right) ?$ (b) Explain why diborane adopts the geometry that it does. (c) What is the significance of the statement that the hydrogen atoms in diborane are described as "hydridic"?

(a) Diborane has a more complex structure than ethane, with boron atoms connected by a bridging hydrogen atom forming a 3-center-2-electron (3C-2E) bond and two other hydrogen atoms connected to each boron atom. Diborane has a trigonal planar arrangement around each boron atom with bond angles of roughly 120 degrees, while ethane has a tetrahedral arrangement with bond angles of 109.5 degrees. (b) The geometry of diborane arises due to the electronic configuration of boron, which can accommodate only 6 electrons in its valence shell. The formation of 3C-2E bonds with bridging hydrogen atoms allows each boron atom to achieve an electron count of six. The trigonal planar arrangement around each boron atom minimizes electron pair repulsion. (c) In diborane, the term "hydridic" refers to the behavior of hydrogen atoms participating in the 3C-2E bonds, as they donate their lone pair of electrons to bond with boron atoms, acquiring a partial negative charge similar to that of a hydride ion (H-).