Mass Of Carbon 12

What is the mass of one mole of carbon-12 atoms? $1$$m o l$ of ${'}^{12} C$ atoms has a mass of $12.00 \cdot g$ precisely.

Why do we use carbon 12 as the basis for the relative atomic mass of elements in the periodic table? Here is a fun, light-hearted take on the story.Sourcesht. A carbon-12 atom is made up of six protons and six neutrons, hence 12 atomic mass units. The mass of the electron is considered negligible, therefore electrons are not counted in measuring an atom's atomic mass. One mole of carbon-12 atoms, or 6.0221415. 10^23 atoms, weighs exactly 12 grams.   Explanation:

The mole is the link between the micro world of atoms and molecules to the macro world of grams and kilograms. By definition, ${N}_{A}$${'}^{12} C$ atoms, i.e. $' A v o g a \mathrm{dr} o ' s \nu m b e r , ' 6.022 \times {10}^{23}$${'}^{12} C$ atoms has a mass of $12.00 \cdot g$.

Mass Of Carbon 12 Atom In Kg

But wait a minute! When I look at the Periodic Table, it gives the equivalent mass of $C$ as $12.011 \cdot g \cdot m o {l}^{-} 1$. Why is there a discrepancy?