The number of atoms present in one mole of an element is equal to Avogadro number. Which of the following element contains the greatest number of atoms?

Question

Philoid · Accepted Answer

The molecular weights of the given elements are as follows:

He = 4, Na = 23, Ca = 40.

To check which element has most atoms, we need to check the number of moles present in each option. The highest number of moles mean the most atoms present.

No. of moles = Given weight/molecular weight of the element

For 4g He, no. of moles are 4/4 = 1 mol.

For 46g Na, no. of moles are 46/23 = 2 mol.

For 0.40g Ca, no. of moles are 0.4/40 = 0.01 mol.

For 12g He, no. of moles are 12/4 = 3 mol.

Therefore, 12g He contains the most number of atoms.

The correct answer is (iv).