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 ?

(a) 4 g He (b) 46 g Na (c) 0.40 g Ca (d) 12 g He

Q. 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?

Q. The number of sulphur atoms present in $0.2$ mole of sodium thiosulphate is: $(N=$ Avogadro number)

Q. The atomic number of an element is equal to the number of protons present in an atom.

Q. One mole of an element contains $4.2\times {10}^{24}$ electrons. What is the atomic number of the element?

Q. Fill in the following blanks :
(a) 1 mole contains ...................... atoms, molecules or ions of a substance.
(b) A mole represents an ..................... number of particles of a substance.
(c) 60 g of carbon element are ................... moles of carbon atoms.
(d) 0.5 mole of calcium element has a mass of ......................
(e) 64 g of oxygen gas contains ....................... moles of oxygen atoms.