Why do we need to giving name for organisms

By name I’m assuming you mean scientific name instead of common name

Every known species is given a two part scientific name. These names are important because they allow people from all over the world to be able to communicate about animal species in a way that everybody can understand. Scientists can also use scientific names to help classify species.

well we can't tell you because we cant see the time give a screen shot or something.

the relative atomic mass of an element is the mass of one atom of that element, relative to 1/12th of the mass of a  1212c atom. to convert to an absolute mass in kg, it is necessary to multiply by  1.661×10−271.661×10−27.

the relative atomic mass is roughly equal to the number of neutrons, plus the number of protons, in the nucleus of the atom.

for elements with more than one stable isotope (different types of nucleus with different numbers of neutrons but the same number of protons), the quoted mass is usually the average mass, weighted by the relative abundance of the different isotopes.