Final answer:
The atomic mass of hydrogen is 1.00794 because it is an average of the masses of its isotopes calculated using their relative abundances, and this value reflects the precision of scientific measurements. Scientists use the atomic mass unit and scientific notation for convenience in representing and comparing the very small masses of atoms.
Step-by-step explanation:
The atomic mass of hydrogen is reported as 1.00794 rather than being rounded off to 1 due to the presence of isotopes. Hydrogen has three isotopes: protium, deuterium, and tritium, with atomic masses of approximately 1 u, 2 u, and 3 u, respectively. When calculating the average atomic mass, the relative abundances of hydrogen's isotopes are taken into account, resulting in the weighted average we see on the periodic table.
The atomic mass unit (amu) is a standard unit of measurement used in chemistry to express atomic and molecular masses. It is based on the carbon-12 isotope, where one amu is defined as one twelfth of the mass of a carbon-12 atom.
To make calculations more convenient, scientists often use scientific notation to express the mass of atoms in a way that is easier to compare and manipulate. An example of scientific notation is writing the mass of a hydrogen atom as 1.67 × 10-27 kg, which simplifies the representation of such a small number. Using this notation, any number, no matter how large or small, can be easily worked with in equations and comparisons without cumbersome decimals.
Understanding the concept of significant figures is crucial as well. The exact value of the atomic mass of hydrogen is reported to many decimal places to reflect the precision of scientific measurements and the slight variations due to the presence of different isotopes.