* It is formed by the chemical combination of two or more different elements. In this case, hydrogen (H) and bromine (Br) are chemically bonded together.
* The elements in a compound are present in a fixed ratio. The ratio of hydrogen to bromine in HBr is always 1:1.
* The compound has properties that are distinct from the elements that make it up. For example, HBr is a gas at room temperature, while hydrogen is a gas and bromine is a liquid.
Therefore, hydrogen bromide is not just a mixture of hydrogen and bromine, but a new substance with its own unique chemical and physical properties. This is why it is classified as a compound.
