Question

What is the mass of 1 atom of oxygen?
(A) $$3.66\times {10}^{-23}g$$
(B) $$2.66\times {10}^{-23}g$$
(C) $$4.66\times {10}^{-23}g$$
(D) $$2.66\times {10}^{23}g$$

Answer 1

Hint: We know that atomic mass of oxygen is 16 g/mol and atomic number is 8. And one mole of oxygen has $$6.022\times {10}^{23}$$ number of atoms.

Complete step by step solution:
- Here, we have to calculate the mass or weight of 1 atom of oxygen. And we know that the atomic number of oxygen is 8. It means oxygen has 8 electrons and 8 protons and the number of protons tells us the identity of the element,because the number of protons is the same as the atomic number. So, the atomic mass or atomic weight of oxygen is 8+8=16 g/mol. And one mol of oxygen contains a number of atoms equal to Avogadro number (N) that is $$6.022\times {10}^{23}mo{l}^{-1}$$.
So, atomic mass of $$(O_2)$$ atoms of oxygen is equal to 16 g
So, the weight / mass of one atom of oxygen is equal to atomic mass / Avogadro number (N)
= 16 (g/mol)/ $$6.022\times {10}^{23}mo{l}^{-1}$$
= $$2.66\times {10}^{-23}g$$
So, the correct answer is “B”

Note: In the calculation you should be careful that atomic mass is not equal to atomic number, it is the sum of electrons and protons. Here, we are talking about the oxygen $$(O)$$ element, not about the oxygen molecule $$(O_2)$$.