What is the mass of a proton expressed as?

The mass of a proton is correctly expressed as (1.67262171 \times 10^{-27}) kg. This value represents the direct measurement of a proton's mass in kilograms and is significant for calculations involving atomic and subatomic particles. The precision of this figure indicates the mass's importance in various physical calculations, such as determining the mass of atoms and molecules where protons are a foundational component.

In atomic physics, the mass of protons plays a crucial role in determining atomic mass and the behavior of elements in chemical reactions. For example, the proton's mass significantly influences the mass of the nucleus of an atom, as protons (along with neutrons) contribute primarily to the atomic mass, while electrons have negligible mass in comparison.

Other options present alternative representations or values that do not accurately describe the mass of a proton in the context provided. For instance, (1.67 , \text{kg}) is not representative of a proton's mass but rather the mass of an object many orders of magnitude larger. The value (9.11 \times 10^{-31} , \text{kg}) represents the mass of an electron, not a proton. Lastly, (1.008 , u\