Hydrogen has the lowest density.
<span>The s sublevel has just one orbital, so can contain 2 electrons max. The p sublevel has 3 orbitals, so can contain 6 electrons max. The d sublevel has 5 orbitals, so can contain 10 electrons max. And the 4 sublevel has 7 orbitals, so can contain 14 electrons max.
So, having this in mind, 10 electrons in total can be contained in the 4d sublevel.
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No of moles of fe2o3 = 16.5/(55.8x2+16x3)=0.103mols
No. Of moles of iron= 0.103 x 2 = 0.206mols
Mass of iron = 0.206 x 55.8 = 11.5g
