A mole of atoms is 6.022 x 10^23 atoms. This number is known as Avogadro's constant. It is named for the Italian scientist and scholar Amedeo Avogadro (1776-1856). Avogadro proposed that two different gases in equal volumes should have the same number of molecules, by which he was able to relate the molecular weights of the two gases to the ratio of their densities. Use Avogadro's constant to easily convert one or more atoms of any element to grams.
- Periodic table of the elements
- Scientific calculator
Write on a piece of paper the name of an element that interests you and the number of atoms of that element you wish to convert to grams. For example, you write "Seven atoms of lithium."
Find the element that interests you in an online periodic table (see Resources) or any chemistry textbook. For example, you find the element lithium (Li) in the first column of the periodic table, second from the top.
Read the number under the symbol for lithium. For example, you read 6.941.
Divide the number under the symbol of the element by 6.022 x 10^23 using a scientific calculator. For example, 6.941/(6.022 x 10^23) = 1.152 x 10^-23.
Multiply your answer times the number of atoms you wrote on the piece of paper. For example, (1.152 x 10^-23) x 7 = 8.068 x 10^-23. Seven atoms of lithium weigh approximately 8.07 x 10^-23 grams.