Question

Which has more number of atoms 100g of $Na$ or 100g of Fe?

Answer 1

Hint: To calculate the number of atoms in a sample, find out how many moles of the element that sample contains. A mole is a unit equal to Avogadro’s number. The weight of one mole of an element (its molar mass) is equal to its atomic weight in grams.

Formula used:
Number of moles $ = \dfrac{{given\, mass}}{{molar\, mass}}$
Number of atoms =Number of moles $ \times {N_A}$ (${N_A}$ =Avogadro’s number)

Complete step by step answer:
The mole concept is basically a convenient method of expressing the amount of a substance. Moreover, while dealing with the particles at an atomic (or molecular) level, even one gram of a pure element is known to contain a huge number of atoms and in such cases the mole concept is widely used.
Now, we have been given that the,
Mass of Na $ = 100g$
Molar mass of Na $ = 23g$
Therefore according to the formula,
Number of moles $ = \dfrac{{100}}{{23}} = 4.347$
Hence, number of atoms $ = 4.35 \times {N_A}$
Now,
Mass of Fe $ = 100g$ (given)
Molar mass of Fe $ = 56g$
Therefore,
Number of moles of Fe $ = \dfrac{{100}}{{56}} = 2.10$
Number of atoms of Fe $ = 2.10 \times {N_A}$
So, we have seen that Na has more numbers of atoms.

Note:
Atoms are the building blocks of matter, and they can be connected to make molecules. Because atoms, molecules and other particles are extremely small, we need a lot to even weigh them and that’s why chemists use the word known as “mole”.