Here's why:
* Structure: HBr consists of one hydrogen atom and one bromine atom.
* Bonding: The hydrogen atom shares its single electron with the bromine atom, forming a single covalent bond.
* Electron Pairs: The bromine atom has seven valence electrons, with one being involved in the bond with hydrogen. This leaves three lone pairs of electrons around the bromine atom.
* Repulsion: The lone pairs of electrons on bromine exert repulsion on the H-Br bond, pushing the hydrogen atom as far away as possible.
* Linear Geometry: This repulsion leads to a linear geometry where the hydrogen atom and bromine atom are positioned on opposite sides of the bromine atom, creating a straight line.
